Abstract
Background
Postpartum depression (PPD) affects approximately 10% to 20% of women during the first 4 weeks of the postpartum period and is characterized by labile mood with prominent anxiety and irritability, insomnia,and depressive mood. During the postpartum period, elevated ovarian hormones abruptly decrease to the early follicular phase levels that are postulated to play a major role in triggering PPD. However, the underlying neurobiological mechanisms that contribute to PPD have not been determined.
Methods
In the present study, we examined the effect of ovarian steroids, administered at levels that occur during human pregnancy followed by rapid withdrawal to simulate postpartum conditions, on behavior and gene expression in the rat.
Results
The results of behavioral testing reveal that the hormone-simulated postpartum treatment results in the development of a phenotype relevant to PPD, including vulnerability for helplessness, increased anxiety, and aggression. Real-time quantitative polymerase chain reaction (PCR) demonstrated transient regulation of several genes, including Ca2+/calmodulin-dependent protein kinase II (CAMKII), serotonin transporter (SERT), myocyte enhancer factor 2A (MEF2A), brain-derived neurotrophic factor (BDNF), gamma-aminobutyric acid type A receptor α4 (GABAARA4), mothers against decapentaplegic homolog 4 (SMAD4), and aquaporin 4 (AQP4) that could underlie these behavioral effects.
Conclusions
These studies provide an improved understanding of the effects of withdrawal from high doses of ovarian hormones on behavior and gene expression changes in the brain that could contribute to the pathophysiology of PPD.
Keywords: Aggression, anxiety, behavior, depression, gene profiling, postpartum depression
Postpartum depression (PPD) is a serious medical condition that affects approximately 10% to 20% of mothers during the first 4 weeks after delivery (1). Symptoms of PPD can include labile mood with prominent anxiety and irritability and depressive mood (2,3). Increased aggression and infanticidal thoughts are mainly linked to postpartum psychosis (4,5), which takes the form of mania or severe depression and complicates one in 1000 deliveries (5).
Pregnancy, delivery, and the postpartum period are characterized by robust hormonal change. By the end of third trimester, plasma estrogen and progesterone rise gradually and reach levels approximately 50-fold and 10-fold higher than maximal menstrual cycle levels, respectively. After parturition, these hormones rapidly drop to early follicular phase levels by days 3 to 7 (3). These endocrine events are purported to play a major role in triggering PPD. A pharmacological model of PPD supports this hypothesis; simulating the postpartum state by administrating pregnancy levels of gonadal steroids and rapidly withdrawing them significantly increases the incidence of depression in women with a history of PPD more than in nondepressed women. Although statistically not significant, the scores of depression scales are higher in the withdrawal period in nonde-pressed women, indicating that these endocrine events provoke mood changes in postpartum women (6). However, the underlying neurobiological mechanisms that contribute to PPD have not been determined.
Several studies have been conducted to address this issue using rat models (7–9). One study found an antidepressant-like response in the forced swim test (FST) in the early, but not the late, pregnancy/postpartum period (7). Another study examined the influence of hormone-simulated pseudopregnancy (HSP) to investigate the withdrawal effect of gonadal steroids on the FST (8,9). Ovariectomized rats were administrated 17β-estradiol benzoate (2.5 µg) and progesterone (4 mg) for 16 days, followed by 8 days of a high dose (50 µg/day) 17β-estradiol benzoate treatment to mimic the rat pregnancy, combined with different time periods of withdrawal. The results demonstrate that rats receiving HSP followed by withdrawal exhibit significantly decreased antidepressant-like responses in the FST. However, this regimen was based on the plasma concentration of estrogen and progesterone that occurs in the course of rat pregnancy, where progesterone peaks during the middle of gestation and falls to estrous cycle levels by the time of delivery (10). Conversely in humans, both estrogen and progesterone increase gradually throughout the pregnancy (11). Progesterone has been shown to alter neurotransmission, indicating a crucial role in the pathophysiology of PPD (3). Thus, novel strategies may be necessary to address the pathophysiology of human PPD.
Based on these considerations, we have developed a novel strategy using endocrine conditions that mimic human pregnancy and the postpartum period. We examine the influence of a high dose of estrogen and progesterone and rapid withdrawal on behavioral alterations in models of depression, anxiety, and aggression, all symptoms of PPD, and gene expression changes. We refer to this as hormone-simulated pseudopregancy-human (HSP-H) and the withdrawal period as hormone-simulated postpartum period-human (HSPP-H). The results identify a behavioral phenotype consistent with the symptoms of PPD and novel gene expression changes that could contribute to PPD. Although the use of human endocrine conditions in rodents has limitations, this model will be useful for future studies of this devastating disorder.
Methods and Materials
Animal Treatment
Female Sprague Dawley rats (250 to 280 g, Charles-River Laboratories, Wilmington, Massachusetts) were group housed and maintained on a 12-hour light/dark cycle (7:00 am–7:00 pm lights on) with free access to food and water. All animal use procedures were in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals and were approved by Yale University Animal Care and Use Committee.
Hormone-Simulated Pseudopregnancy-Human and Hormone-Simulated Postpartum Period-Human
Rats underwent ovariectomy (OVX) followed by continuous release pellet implantation (.5 mg of 17β estradiol [E2] and 50 mg of progesterone [P4] 21-day release or placebo) (Innovative Research of America, Sarasota, Florida) under pentobarbital/ atropine anesthesia to mimic serum levels of those during human pregnancy (11). After 21 days treatment, the hormone pellets were completely removed under isoflurane anesthesia. In accordance with previous studies using the rat model of the postpartum period, the 22nd to 28th days were considered as the HSPP-H (7–9). Behavioral tests were conducted in the following experimental groups: placebo treatment (OVX), 21-day treatment of HSP-H, and HSPP-H followed by different periods of hormonal withdrawal (1 day–7 days; HSPP-H/1–7). Separate groups of rats were tested on the forced swim test or the other behavioral tests. Rats that underwent FST were tested only once at each time point. Rats that underwent the open field test (OFT) on withdrawal day 4 were used for further behavioral analysis, i.e., elevated plus maze (EPM) on withdrawal day 5, learned helplessness (LH) or resident intruder test on withdrawal day 7 (Table 1). For gene expression, we used OVX, HSP-H, and HSPP-H/4 rats that were not subjected to the behavioral studies to avoid stress effects. Rats were sacrificed by decapitation, and brains were removed, dissected, and stored at −80°C.
Table 1.
Experimental Timeline
Experimental Group |
HSP Treatment 21 Days |
Withdrawal | Behavioral Tests |
---|---|---|---|
OVX | Placebo | Pellet removal on day 21 | FST on WD day 0, 1, 4, or 07;or |
HSPP-H | E&P | Pellet removal on day 21 | OFT on WD day 4, EPM on WD day 5, and LH or RIT on WD day 28 |
HSP-H | E&P | Sham surgery on day 17 | FST on day 21; or OFT on day 21, EPM on day 22, and LH or RIT on day 24 |
E, estrogen; EPM, elevated plus maze test; FST, forced swim test; HSP-H, hormone-simulated pseudopregancy-human; HSPP-H, hormone-simulated postpartum period-human; LH, learned helplessness test; OFT, open field test; OVX, ovariectomy; P, progesterone; RIT, resident intruder test; WD, withdrawal day.
Learned Helplessness
This test was performed with a shuttle box for active and passive avoidance (Med Associates Inc., St. Albans, Vermont) during light cycle (1:00 pm–5:00 pm). Rats were subjected to 60 inescapable electric foot shocks (.65 mA; 15-sec duration, at random intervals; mean 30 sec; average 22–38 sec) in the shuttle box. Twenty-four hours later, all rats were placed back in the same shuttle box and tested for shuttle escape learning. The testing paradigm used fixed-ratio (FR) trials, first with 5 FR1 trials (one cross) to terminate the grid shock, followed by 25 FR2 trials (two crosses) to terminate the shock. The entire shuttle box escape test session lasted for 45 min per subject. The mean latencies to terminate the shock for the FR1 and FR2 trials were analyzed separately for all experimental groups (OVX, n = 16; HSP-H, n = 18; and HSPP-H/7, n = 17).
Forced Swim Test
This paradigm was performed as described previously (12– 14) during light cycle (1:00 pm–5:00 pm). On day 1, the animals were placed in a Plexiglas cylinder (25 cm diameter × 65 cm height) with water at a depth of 45 cm (24°C –25°C) for 15 min. Then, the rats were removed from water, dried, and kept warm for 30 min. On day 2, the rats were placed back into the water for 5 min, and the sessions were videotaped (OVX, n = 24; other groups, n = 6). A time-sampling technique was used to rate the behavior at the end of each 5 sec period during the 300 sec test session. The behaviors scored in the FST were 1) immobility (rat making only those movements necessary to keep its head above water); 2) swimming (rat staying afloat, pedaling, and making circular movements around the tank); and 3) struggling/climbing (rat making active attempts to escape from the tank).
Open Field Test
Spontaneous locomotor activity was measured in the open field test in a square arena (76.5 × 76.5 × 49 cm) using a standard procedure (15) during the dark cycle (9:00 pm–1:00 am). Animals that underwent OVX, HSP-H, and HSPP-H/4 were used (n = 16/group). The open field was divided into two areas, a peripheral area and a square center (40 × 40 cm). Rats were allowed to explore for 5 min. The test room was dimly illuminated under red light. The computer software (EthoVision; Noldus, Alexandria, Virginia) calculated the distance moved and the time spent in the center of the open field.
Elevated Plus Maze Test
This test was carried out during dark cycle (9:00 pm–1:00 am). This model consists of an elevated (50 cm above the floor) plus-shaped maze with two opposite enclosed and two open arms, measuring 50 cm long and 10 cm wide, placed in a red dimly lit room. The testing procedure was described previously (16). Each animal underwent OVX, HSP-H, and HSPP-H/4 (n = 14/group) was placed in the center of the maze facing a closed arm. An entry into an arm was defined as the animal placing all four paws into it. The cumulative time spent in the open/closed arms and in the center and the number of open-arm and closed-arm entries were recorded through a 5-min session. Data were expressed as the time spent in the open arms, the closed arms, and the center (second); the number of entries to the closed arms; and the total number of entries (open + closed arms).
Resident Intruder Test
Aggression toward an unfamiliar intruder was evaluated as described previously (17–19). This test was carried out during the dark cycle (9:00 pm–1:00 am). A female resident rat that underwent OVX, HSP-H, or HSPP-H/7 treatment (n = 10/group) confronted a naive male intruder rat (240–270 g) for 10 min. A similar paradigm (female resident and smaller male intruder) has been shown to result in significant aggressive behavior in a previous report (19). The behavior of residents during confrontation was videotaped and latency to the first attack was monitored. Frequency and duration of behavioral acts were manually scored for each animal. The following behaviors were distinguished: 1) lateral threat; 2) offensive upright; 3) keep down; 4) clinch; 5) chase; 6) investigating opponent; 7) anogenital sniffing; 8) social grooming/crawl over; 9) mounting; 10) ambulation; 11) rearing; 12) grooming; 13) inactivity; 14) freeze; 15) submissive posture; and 16) keep off. Offensive behavior includes lateral threat, offensive upright, keep down, clinch, and chase. Social explore includes investigating opponent and anogenital sniffing. Social interaction includes social grooming/crawl over and mounting. Nonsocial explore includes ambulation and rearing. The duration of the different behavioral categories was cumulated and expressed as a percentage of the 10-min confrontation.
Real-Time Quantitative Reverse Transcript Polymerase Chain Reaction
To identify the candidate genes that are regulated by HSP-H and HSPP-H, DNA microarray analysis was performed as described previously (20) (Supplement 1). Differential expression of candidate genes obtained from DNA microarray analysis was confirmed by real-time quantitative reverse transcript polymerase chain reaction (RT-PCR). Total RNA (3 µg) from hippocampus, a region that is implicated in the pathophysiology of mood disorders (21), was reverse transcribed using SuperScript II first-strand synthesis system for RT-PCR (Invitrogen, Carlsbad, California). Primers used for RT-PCR are designed using Primer express software (Applied Biosystems, Foster City, California) and listed in Table 2. Real-time quantitative reverse transcript polymerase chain reaction was performed in the ABI PRISM 7900HT fast real-time polymerase chain reaction (PCR) system (Applied Biosystems) using SYBR green detection (QuantiTect SYBR green PCR kit, Qiagen, Valencia, California). The following temperature profile was used: 40 cycles of 15 sec at 95°C followed by 1 min at 60°C. Cycle thresholds were automatically determined within the log-linear phase of the reaction using Sequence Detection Systems (SDS) plate utility software, version 2.2 (Applied Biosystems). The comparative cycle threshold method (ΔCt method) was used to calculate relative expression levels. Briefly, to calculate ΔCt, cycle number at threshold crossing values (Ct) for an internal control housekeeping gene (cyclophilin) was subtracted from Ct for a gene of interest. Each expression value relative to cyclophilin was determined as 2 −ΔCt and normalized by OVX (n = 6/group).
Table 2.
Primers Used for Quantitative Real-Time PCR
Gene ID | Left Primer Sequence | Right Primer Sequence |
---|---|---|
AQP4 | AGATCAGCATCGCCAAGTCT | GGGTGTGACCAGGTAGAGGA |
BDNF | AAGGCTGCAGGGGCATAGAC | TGAACCGCCAGCCAATTCTC |
CAMKIIA | TATCGTCCGACTCCATGACA | CTGGCATCAGCCTCACTGTA |
CAMKIIB | GGCCAGCAAATGCAAAGG | GTTCCCGCAAATCCAAACC |
CAMKIID | CCAAAGACAATGCAGTCAGAAGAG | GACCCCGAACGATGAAAGTG |
CAMKIIG | GCAGGCTTGGTTTGGTTTTG | TCCATAGGGATCTTTCCTCAAGAC |
GABAARA4 | TGAAATCCTGAGGTTGAACAATATG | GACAGATTTCTTTCCATTCCTGAAG |
MEF2A | GCCTCCGCAGGGACTAGTG | GCGCTGGTCAA TGAGTAATCAG |
SERT | ACTGGGCCAGTACCACCG | TCGGGCAGATCTTCCTCC |
SMAD4 | GGCATTGGTGTAGACGACCT | CGGTGGAGGTGAATCTCAA |
AQP4, aquaporin 4; BDNF, brain-derived neurotrophic factor; CAMKII, Ca2+/calmodulin-dependent protein kinase II; GABAARA4, gamma-aminobutyric acid type A receptor α4; MEF2A, myocyte enhancer factor 2A; PCR, polymerase chain reaction; SERT, serotonin transporter; SMAD4, mothers against decapentaplegic homolog 4.
Statistical Analysis
The data obtained in the experiments were analyzed by a one-way analysis of variance (ANOVA), followed by Fisher’s protected least squares difference (PLSD) or Scheffe’s test for the post hoc comparison of the mean. All statistical data in the text are expressed as mean ± SEM; differences were considered statistically significant only if p < .05.
Results
Behavior Analysis
Learned Helplessness Test
Animals exposed to repeated inescapable foot shock (IES) exhibit “helpless” behavior characterized by an inability to respond in a subsequent escapable situation. This escape deficit is reversed by chronic antidepressant treatments (22,23). There were significant effects of treatment on escape failure and escape latency of FR1, FR2, and the mean [F(2,48) = 4.181, p = .0212; F(2,48) = 4.663, p = .0141; F(2,48) = 4.690, p = .0138; F(2,48) = 5.323, p = .0082]. The HSPP-H/7 animals displayed a significantly increased escape failure and latency to escape after exposure to IES compared with OVX. There were no significant behavioral changes between the OVX and HSP-H groups (Figure 1, Table 3). The results demonstrate that the hormonal deprivation subsequent to HSP-H treatment increases helplessness in the LH.
Figure 1.
Influence of HSP-H and HSPP-H on the learned helplessness test. Escape failures, number of crossings, and escape latency (FR1, FR2, and total mean value) were determined. The results are the mean ± SEM (OVX n = 16, HSP-H n = 18, HSPP-H/7 n = 17). ANOVA and Scheffe: *p < .05, difference in comparison with HSP-H, ** p < .01, difference in comparison with HSP-H. Left top to right top, F(2,48) = 4.181, p < .05; F(2,48) = 3.437, p < .05. Left bottom to right bottom, F(2,48) = 4.663, p< .05; F(2,48) = 4.690, p< .05; F(2,48) = 5.323, p< .01. ANOVA, analysis of variance; FR1, fixed-ratio one cross; FR2, fixed-ratio two crosses; HSP-H, hormone-simulated pseudopregancy-human; HSPP-H, hormone-simulated postpartum period-human; OVX, ovariectomy.
Table 3.
Behavioral Profile of HSP-H and HSPP-H Animals
Behavioral Tests | HSP-H | HSPP-H |
---|---|---|
Learned Helplessness | ||
Escape failures | − | + +/helpless |
Escape latency | − | + + |
Forced Swim Test | ||
Immobility | ne | + + + |
Swimming | ne | + |
Struggling/climbing | ne | + + |
Open Field Test | ||
Time in center | ne | ne |
Total distance | ne | ne |
Elevated Plus Maze | ||
Open arm | − | + + + |
Total arm | − − | ne |
Resident Intruder Test | ||
Social behaviors | ne | ne |
Aggression: time | + + + + + | + + + |
latency | + + + | + + + |
HSP-H, hormone-simulated pseudopregancy-human; HSPP-H, hormone-simulated postpartum period-human; ne, no effect; +, indicated behavior induced; −, opposite effect observed.
Forced Swim Test
In this paradigm, the time spent in immobility is typically decreased by antidepressant administration (12). The results revealed significant differences between the groups in mean time spent in immobility and struggling/climbing [F(4,43) = 5.410, p = .0013; F(4,43) = 4.746, p = .0029]. Immobility was significantly decreased in the HSPP-H/4 and HSPP-H/7 groups and struggling/climbing was significantly increased in the HSPP-H/7 group compared with OVX. There was no significant interaction between treatment group and swimming [F(4,43) = 2.317, p = .0724] (Figure 2, Table 3).
Figure 2.
Influence of HSP-H and HSPP-H on the FST. Each behavior (immobility, swimming, struggling/climbing) was scored during the first 5 min of day 2 trials. The results are the mean ± SEM(OVX n = 24;HSP-H,HSPP-H/1,HSPP-H/4, and HSPP-H/7 n = 6each). ANOVA and Scheffe:*p <.05, difference in comparison with OVX. Left to right, F(4,43) = 5.410, p < .005; F(4,43) = 2.317, not significant (ns); F(4,43) = 4.746, p < .005. ANOVA, analysis of variance; FST, forced swim test; HSP-H, hormone-simulated pseudopregancy-human; HSPP-H, hormone-simulated postpartum period-human; ns, not significant; OVX, ovariectomy.
Open Field Test
The open field test, as well as EPM, were conducted to test the possibility that the decreased immobility observed in HSPP-H on the FST was due to increased spontaneous locomotor activity or increased anxiety. Time spent in the center of a novel open field and the distance moved are indications of anxiety and locomotor activity, respectively (15). Four days’ withdrawal was examined, as decreased immobility in the FST was observed at this time point. Hormone-simulated pseudopregancy-human treatment and HSPP-H did not significantly influence time in the center field or the distance moved [F(2,45) = .566, p = .5717; F(2,45) = 1.176, p = .3177], although there was a tendency for a decrease in center time in HSPP-H treated groups (Figure 3, Table 3).
Figure 3.
Influence of HSP-H and HSPP-H on the open field test. Distance moved and the time spent in the center that indicate locomotor activity and anxiety, respectively, were calculated. The results are the mean ± SEM (n = 16/group). Left to right, F(2,45) = .566, ns; F(2,45) = 1.176, ns. HSP-H, hormone-simulated pseudopregancy-human; HSPP-H, hormone-simulated postpartum period-human; ns, not significant.
Elevated Plus Maze Test
This test relies on the inherent conflict between exploration and avoidance of a novel area. The time spent on the open arms and the number of entries into the open arms are inversely correlated with anxiety. Previous studies demonstrate that anxiolytic agents increase and that anxiogenic drugs decrease the time and entries in the open arms (16). The amount of time spent in the open arms of the OVX females is similar to that in previous reports (24,25). Analysis of variance revealed a significant effect of treatment on time spent in open arms and number of total entries [F(2,27) = 15.119, p< .0001; F(2,27) = 16.569, p < .0001]. Hormone-simulated postpartum period-hu-man/5 animals spent significantly less time in the open arms than HSP-H animals, whereas HSP-H rats showed a significant increase in the number of entries compared with OVX (Figure 4, Table 3).
Figure 4.
Influence of HSP-H and HSPP-H on the elevated plus maze test. This test was conducted to evaluate the influence of HSP-H and HSPP-H treatments on anxiety. The results are the mean ± SEM (n = 14/group). ANOVA and Scheffe: * p< .05, difference in comparison with HSP-H. †p< .05, difference in comparison with OVX. Left top to right top, F(2,39) = 3.297, p< .05; F(2,39) = 2.744, ns; F(2,39) = .425, ns. Left bottom to right bottom, F(2,39) = 3.020, ns; F(2,39) = 4.073, p< .05. ANOVA, analysis of variance; HSP-H, hormone-simulated pseudopregancy-human; HSPP-H, hormone-simulated postpartum period-human; ns, not significant; OVX, ovariectomy.
Resident Intruder Test
This test was performed to evaluate whether maternal aggression is induced by HSP-H or HSPP-H. Intrusion of an unfamiliar rat into the home cage provokes a typical offensive and aggressive behavioral pattern of the resident rat (18). The results revealed a significant effect of treatments on offensive behavior and attack latency [F(2,27) = 15.119, p< .0001; F(2,27) = 16.569, p< .0001]. Hormone-simulated pseudopregancy-human animals showed a significantly increased time in offensive behaviors toward the intruder compared with OVX and HSPP-H/7 animals. Both HSP-H and HSPP-H/7 showed a significant reduction in the attack latency to the intruder. There was no significant influence on other social and nonsocial behaviors (Figure 5, Table 3). These results indicate that the HSP-H treatment induces aggression in female rats that persists for at least 7 days after withdrawal.
Figure 5.
Influence of HSP-H and HSPP-H on the resident intruder test. The results are the mean ± SEM (n = 10/group). ANOVA and Scheffe: *p< .01,**p< .001, ***p<.0001, difference in comparison with OVX. †p<.05, difference in comparison with HSP-H. Left top to right top, F(2,27) = 15.119,p<.0001;F(2,27) = .385, ns;F(2,27) = .746, ns. Left bottom to right bottom, F(2,27) = .250, ns;F(2,27) = 3.449, p< .05;F(2,27) = 2.291, ns;F(2,27) = 16.569, p < .0001. ANOVA, analysis of variance; HSP-H, hormone-simulated pseudopregancy-human; HSPP-H, hormone-simulated postpartum period-human; ns, not significant; OVX, ovariectomy.
Gene Expression: RT-PCR
Differential expression of candidate genes obtained from microarray results (see Supplement 1 for details) was confirmed using real-time quantitative RT-PCR. The results revealed that Ca2+/calmodulin-dependent protein kinase II8 (CAMKIID) is significantly upregulated by HSP-H and returns to OVX levels after 4 days withdrawal. Ca2+/calmodulin-dependent protein kinase IIα (CAMKIIA) expression was significantly decreased in the HSPP-H/4 group compared with OVX and HSP-H. Other CAMKII subtypes, including CAMKIIβ (CAMKIIB) and CAMKII γ (CAMKIIG), were not regulated. The expression of the serotonin transporter (SERT) was significantly increased by HSP-H and returned to OVX levels after 4 days withdrawal. Myocyte enhancer factor 2A (MEF2A) and brain-derived neurotrophic factor (BDNF) expressions were significantly attenuated after hormonal deprivation but were not altered by the HSP-H per se. Gamma-aminobutyric acid type A receptor α4 (GABAARA4) and aquaporin 4 (AQP4) expressions were significantly downregulated by HSP-H and returned to OVX levels after 4 days withdrawal. Expression of mothers against decapentaplegic homolog 4 (SMAD4) was significantly decreased in the HSP-H group compared with OVX (Figure 6, Table 4). Other genes that have been implicated in mood disorders, including the glucocorticoid receptor (26), vascular endothelial growth factor (VEGF) (27), glycogen synthase kinase 3β (GSK3B), Akt/protein kinase B (28), and interleukin-18 (29), were not altered in the present model (not shown).
Figure 6.
Real-time PCR of selected genes identified by microarray to be regulated by HSP-H and HSPP-H. Fold change was calculated as 2−ΔCt and normalized by OVX as described in Methods and Materials. The results are the mean ± SEM (n = 6/group). ANOVA and Fisher’s PLSD: * p< .05. †p< .05, ††p< .01, difference in comparison with HSP-H. (A) CAMKIIs: Left to right, F(2,15) = 5.239, p< .05; F(2,15) = 2.207, ns; F(2,15) = 1.874, ns; F(2,15) = 4.648, p< .05. (B) Upregulated genes: Left to right, F(2,15) = 3.398, p< .05;F(2,15) = 3.732, p< .05. (C) Downregulated genes: Left to right, F(2,15) = 3.889, p = .05;F(2,15) = 4.059, p< .05; F(2,15) = 3.695, p< .05; F(2,15) = 4.424, p< .05. ANOVA, analysis of variance; CAMKII, Ca2+/calmodulin-dependent protein kinase II; HSP-H, hormone-simulated pseudopregancy-human; HSPP-H, hormone-simulated postpartum period-human; ns, not significant; OVX, ovariectomy; PCR, polymerase chain reaction; PSLD, protected least squares difference.
Table 4.
Genes Regulated by HSP-H and HSPP-H Treatments
Fold Change (ANOVA and Fisher PLSD p Value) |
||||
---|---|---|---|---|
Protein | Gene ID | HSP-H/OVX | HSPP-H/OVX | HSPP-H/HSP-H |
Ca2+/Calmodulin-dependent Protein Kinase II α | CAMKIIA | + 1.11 (ns) | − 1.61 (.0242) | − 1.78 (.0147) |
Ca2+/Calmodulin-dependent Protein Kinase II β | CAMKIIB | + 1.19 (ns) | − 1.18 (ns) | − 1.41 (ns) |
Ca2+/Calmodulin-dependent Protein Kinase II δ | CAMKIID | + 1.61 (.0280) | − 1.19 (ns) | − 1.92 (.0078) |
Ca2+/Calmodulin-dependent Protein Kinase II γ | CAMKIIG | + 1.16 (ns) | − 1.20 (ns) | − 1.39 (ns) |
γ-Amino-Butyric Acid Type A Receptor α4 | GABAARA4 | − 1.24 (.0318) | + 1.01 (ns) | + 1.25 (.0219) |
Serotonin Transporter | SERT | + 2.58 (.0425) | + 1.21 (ns) | − 2.13 (.0261) |
Aquaporin 4 | AQP4 | − 1.48 (.0282) | + 1.04 (ns) | + 1.52 (.0164) |
Myocyte Enhancer Factor 2A | MEF2A | + 1.49 (ns) | − 1.15 (ns) | − 1.72 (.0206) |
SMAD, Mothers Against Decapentaplegic Homolog 4 | SMAD4 | − 1.32 (.0205) | − 1.23 (ns) | + 1.07 (ns) |
Brain-Derived Neurotrophic Factor | BDNF | + 1.08 (ns) | − 1.36 (ns) | − 1.47 (.0170) |
ANOVA, analysis of variance; AQP4, aquaporin 4; BDNF, brain-derived neurotrophic factor; CAMKII, Ca2+/calmodulin-dependent protein kinase II; GABAARA4, gamma-aminobutyric acid type A receptor α4; HSP-H, hormone-simulated pseudopregancy-human; HSPP-H, hormone-simulated postpartum period-human; MEF2A, myocyte enhancer factor 2A; ns, not significant; PSLD, protected least squares difference; SERT, serotonin transporter; SMAD4, mothers against decapentaplegic homolog 4.
Discussion
Behavioral Studies
In the LH behavioral despair model, the HSPP-H animals showed significantly increased escape failures and latency to escape, interpreted as a measure of helplessness or depressive-like behavior. Conversely, in the FST, the HSPP-H animals displayed a significant decrease in immobility, which is typically interpreted as a measure of antidepressant activity (12,30). Although the opposing effects observed in LH and FST tests appear contradictory, there are conflicting reports on FST behavior in postpartum rat models. One study reported decreased immobility in early pregnancy and no effect in postpartum (7), while other studies have reported that an HSPP-H regimen that mimics rat pregnancy (i.e., progesterone [4 mg/day] terminated in day 14), increased immobility (8,9). The differences in the progesterone treatment between the latter and the present study (continuous release pellet, 50 mg/21 days) could underlie the behavioral differences observed.
To examine the possibility that the decreased immobility observed in HSPP-H on the FST was influenced by altered spontaneous locomotor activity or anxiety, we examined behaviors in the OFT and EPM. The results of the OFT demonstrate that the HSP-H, with or without withdrawal, has no significant effect on locomotor activity. Hormone-simulated postpartum period-human showed a small trend for decreased time spent in the center, indicative of increased anxiety. This was confirmed by the EPM, which demonstrates a highly significant increase in anxiety, indicating that hormone withdrawal also leads to increased anxiety. The reason for the discrepancy between the OFT and EPM is not clear but could be related to the greater level of anxiety that is encountered in the open arm of the EPM relative to that in the open field. It is also possible that the elevated anxiety observed in the HSPP-H withdrawal group could contribute to the altered behavior in the FST. This is supported by previous studies demonstrating that agents that increase anxiety, including pentylenetetrazol, a corticotropin-releasing factor receptor type 1 (CRF1) agonist, or a diazepam inverse agonist, all decrease immobility time in the FST, similar to the effects observed in the present study (31–33). In addition, exposure to stress produces a state where subsequent antidepressant treatment increases, instead of decreases, immobility (34). These studies indicate that enhanced anxiety could increase struggling and climbing in the FST and thereby account for the observed decrease in immobility. In summary, the data are consistent with the hypothesis that hormone withdrawal increases behavioral despair in the LH paradigm and that this is accompanied by increased anxiety in situations that induce a relatively high state of anxiety, such as the open arm in the EPM and water/swimming in the FST.
The elevated anxiety observed in the EPM is in line with the clinical features of PPD; women with PPD are more likely to present with anxious features compared with patients with nonpostpartum depression (35). This finding is also supported by animal studies demonstrating that pseudopregnant rats that undergo estrogen and progesterone withdrawal display an enhanced level of anxiety (36). Progesterone elicits an anxiolytic effect through its metabolite allopregnanolone, which interacts with the gamma-aminobutyric acid type A receptor (GABAAR) in a benzodiazepine-like manner (37–39). Therefore, it is possible that progesterone deprivation leads to a rebound increase in anxiety.
The resident intruder test revealed increased aggression toward the intruder in the HSP-H and the HSPP-H animals compared with the OVX animals. Previous studies are in agreement with this finding, reporting that in rodents the dam shows an enhanced aggressive behavior toward an intruder after parturition (40–43), although reduced anxiety has been reported (40,44). There is clinical evidence that the symptoms of PPD may include anxiety accompanied by aggression, sometimes resulting in obsessions of child harm (5). Taken together, the increased anxiety and aggression, as well as depressive-like behavior, observed in the current PPD model are more relevant to the clinical manifestations of PPD than those observed in models that more closely approximate the rodent hormone levels and changes.
Gene Expression Analysis
Ca2+/calmodulin-dependent protein kinase II is a mediator of diverse physiological responses induced by Ca2+-linked signaling that exists in four known isoforms, CAMKIIA, CAMKIIB, CAMKIID, and CAMKIIG (45). Ca2+/calmodulin-dependent protein kinase IIA and CAMKIIB are neuron specific, whereas CAMKIID and CAMKIIG are ubiquitous (46). Ca2+/calmodulin-dependent protein kinase IIA, the most enriched form, plays a role in synaptic plasticity and memory (47–50) and neurotransmission (51). Postmortem brain studies have suggested the involvement of CAMKIIs in the pathophysiology of psychiatric conditions including bipolar disorder (52), Alzheimer disease (53), schizophrenia, and depression (54). Furthermore, chronic antidepressant treatment increases CAMKII activity (55,56). Our results revealed transient CAMKIID upregulation and decreased CAMKIIA expression during the course of HSP followed by withdrawal, suggestive of possible involvement of these kinases in the pathophysiology of PPD.
Serotonin transporter regulates extracellular serotonin levels (57) and is a primary molecular target of antidepressants (58). Serotonin transporter gene expression is regulated by cyclic adenosine monophosphate (cAMP)-dependent (59), as well as cyclic guanosine monophosphate (cGMP)-dependent, pathways (60); S100β, which is astrocyte-specific Ca2+-binding protein (61); and steroid hormones including estrogen (59,62). The adaptive downregulation of this protein is postulated to play a major role in the clinical response of antidepressants (63). In our animal model of PPD, we observed a transient increase and a rapid decrease to basal levels of SERT expression in response to HSP-H followed by withdrawal. The large fluctuation of SERT expression that occurs during the perinatal period could contribute to the development and expression of mood disorders.
Myocyte enhancer factor 2A is a transcription factor that plays a critical role in cell differentiation during development of skeletal muscle, as well as the central nervous system (CNS) (64). Although there are no reports of a relationship between MEF2A and mood disorders, our results suggest that decreased MEF2A gene expression after gonadal steroid deprivation could also contribute to the behavioral changes observed.
Brain-derived neurotrophic factor is a small basic protein that supports the survival of neurons (65). Several lines of evidence suggest the involvement of BDNF in the neurobiological basis of depression and antidepressant response. Stress decreases and antidepressant treatment increases the expression of BDNF (66,67), and BDNF infusions produce an antidepressant response in rodent behavioral models (14,23,68). The present results demonstrate that BDNF expression is decreased during the HSPP-H period, an effect that could contribute to the depressive-like behavior observed in the learned helplessness paradigm and possibly the other behavioral responses.
The gamma-aminobutyric acid (GABA) gated chloride channel A (GABAAR) is a pentamer composed of various combinations of α (1–6), β (1–3), γ (1–3), δ, and ε subunits that mediate inhibitory neurotransmission in the CNS (69). Withdrawal from the progesterone derivative allopregnanolone increases both the messenger RNA (mRNA) and protein of GABAAR α4 (GABAARA4), a subunit that is relatively insensitive to benzodiazepines (36,70) and has been reported to be involved in the pathophysiology of PPD and premenstrual syndrome (3). The results of the present study are consistent with these findings and demonstrate that GABAARA4 expression is increased in HSPP-H animals compared with HSP-H.
Aquaporin 4 is the predominant water channel in the brain and might be related to the formation of blood-brain barrier (71). Increased AQP4 expression has been reported in postmortem brain of bipolar disorder subjects (72). Our results reveal a transient decrease of AQP4 expression by HSP-H followed by rapid recovery.
Mothers against decapentaplegic homolog 4 (SMAD4) is an essential intracellular component of transforming growth factor beta (TGF-β) signaling (73). Enhancement of TGF-β signaling by activin, a member of TGF-β superfamily, promotes an antide-pressant-like effect (74). In the present study, SMAD4 expression is decreased by HSP-H, suggesting that the behavioral changes in the postpartum model could be precipitated by attenuated TGF-β signaling.
In summary, we have established a novel animal model of PPD that mimics human pregnancy and the postpartum period. Although there are limitations of our study, including the difference of gestation length between human and rat and the levels of estrogen and progesterone, the results demonstrate a behavioral phenotype that is relevant to PPD symptoms, including increased anxiety, increased aggression, and vulnerability for learned helplessness. Analysis of gene expression reveals transient regulation of several genes encoding regulatory proteins that might be susceptible genes for PPD, a hypothesis to be tested in future studies. We believe these studies provide an improved understanding of the effects of ovarian hormones and withdrawal on behavioral and gene expression changes in the brain that underlie the pathophysiology of PPD.
Supplementary Material
Acknowledgments
This work was supported by United States Public Health Service Grants MH45481 and 2 PO1 MH25642, Veterans Administration National Center Grant for Post-Traumatic Stress Disorder, the Connecticut Mental Health Center, and a Mitsubishi Pharma Research Foundation Award to SS.
Footnotes
The authors reported no biomedical financial interests or potential conflicts of interest.
Supplementary material cited in this article is available online.
References
- 1.American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 4th ed. Washington, DC: American Psychiatric Association; 2000. Text Revision. [Google Scholar]
- 2.Miller LJ. Postpartum depression. JAMA. 2002;287:762–765. doi: 10.1001/jama.287.6.762. [DOI] [PubMed] [Google Scholar]
- 3.Bloch M, Daly RC, Rubinow DR. Endocrine factors in the etiology of postpartum depression. Compr Psychiatry. 2003;44:234–246. doi: 10.1016/S0010-440X(03)00034-8. [DOI] [PubMed] [Google Scholar]
- 4.Reck C, Hunt A, Fuchs T, Weiss R, Noon A, Moehler E, et al. Interactive regulation of affect in postpartum depressed mothers and their infants: An overview. Psychopathology. 2004;37:272–280. doi: 10.1159/000081983. [DOI] [PubMed] [Google Scholar]
- 5.Brockington I. Postpartum psychiatric disorders. Lancet. 2004;363:303–310. doi: 10.1016/S0140-6736(03)15390-1. [DOI] [PubMed] [Google Scholar]
- 6.Bloch M, Schmidt PJ, Danaceau M, Murphy J, Nieman L, Rubinow DR. Effect of gonadal steroids in women with a history of postpartum depression. Am J Psychiatry. 2000;157:924–930. doi: 10.1176/appi.ajp.157.6.924. [DOI] [PubMed] [Google Scholar]
- 7.Molina-Hernandez M, Tellez-Alcantara NP. Antidepressant-like actions of pregnancy, and progesterone in Wistar rats forced to swim. Psychoneuroendocrinology. 2001;26:479–491. doi: 10.1016/s0306-4530(01)00007-5. [DOI] [PubMed] [Google Scholar]
- 8.Galea LA, Wide JK, Barr AM. Estradiol alleviates depressive-like symptoms in a novel animal model of post-partum depression. Behav Brain Res. 2001;122:1–9. doi: 10.1016/s0166-4328(01)00170-x. [DOI] [PubMed] [Google Scholar]
- 9.Stoffel EC, Craft RM. Ovarian hormone withdrawal-induced “depression” in female rats. Physiol Behav. 2004;83:505–513. doi: 10.1016/j.physbeh.2004.08.033. [DOI] [PubMed] [Google Scholar]
- 10.Lye SJ, Nicholson BJ, Mascarenhas M, MacKenzie L, Petrocelli T. Increased expression of connexin-43 in the rat myometrium during labor is associated with an increase in the plasma estrogen:progesterone ratio. Endocrinology. 1993;132:2380–2386. doi: 10.1210/endo.132.6.8389279. [DOI] [PubMed] [Google Scholar]
- 11.Birzniece V, Johansson IM, Wang MD, Seckl JR, Bäckström T, Olsson T. Serotonin 5-HT1A receptor mRNA expression in dorsal hippocampus and raphe nuclei after gonadal hormone manipulation in female rats. Neuroendocrinology. 2001;74:135–142. doi: 10.1159/000054679. [DOI] [PubMed] [Google Scholar]
- 12.Porsolt RD, Le Pichon M, Jalfre M. Depression: A new animal model sensitive to antidepressant treatments. Nature. 1977;266:730–732. doi: 10.1038/266730a0. [DOI] [PubMed] [Google Scholar]
- 13.Detke MJ, Rickels M, Lucki I. Active behaviors in the rat forced swimming test differentially produced by serotonergic and noradrenergic antidepressants. Psychopharmacology (Berl) 1995;121:66–72. doi: 10.1007/BF02245592. [DOI] [PubMed] [Google Scholar]
- 14.Siuciak JA, Lewis DR, Wiegand SJ, Lindsay RM. Antidepressant-like effect of brain-derived neurotrophic factor (BDNF) Pharmacol Biochem Behav. 1997;56:131–137. doi: 10.1016/S0091-3057(96)00169-4. [DOI] [PubMed] [Google Scholar]
- 15.Lacroix L, Broersen LM, Weiner I, Feldon J. The effects of excitotoxic lesion of the medial prefrontal cortex on latent inhibition, prepulse inhibition, food hoarding elevated plus maze, active avoidance and locomotor activity in the rat. Neuroscience. 1998;84:431–442. doi: 10.1016/s0306-4522(97)00521-6. [DOI] [PubMed] [Google Scholar]
- 16.File SE, Lippa AS, Beer B, Lippa MT. Current Protocols in Neuroscience. Hoboken, New Jersey: John Wiley & Sons; 2004. Animal tests of anxiety; pp. 8.3.1–8.3.22. [DOI] [PubMed] [Google Scholar]
- 17.Miczek KA. A new test for aggression in rats without aversive stimulation: Differential effects of d-amphetamine and cocaine. Psycho-pharmacology (Berl) 1979;60:253–259. doi: 10.1007/BF00426664. [DOI] [PubMed] [Google Scholar]
- 18.de Boer SF, Lesourd M, Mocaer E, Koolhaas JM. Selective antiaggressive effect of alnespirone in resident-intruder test are mediated via 5-hydroxytryptamine 1A receptors: A comparative pharmacological study with 8-hydroxy-2-dipropylaminotetralin, ipsapirone, buspirone, eltoprazine, and WAY-100635. J Pharmacol Exp Ther. 1999;288:1125–1133. [PubMed] [Google Scholar]
- 19.Consiglio AR, Borsoi A, Pereira GA, Lucion AB. Effects of oxytocin microinjected into the central amygdaloid nucleus and bed nucleus of stria terminalis on maternal aggressive behavior in rats. Physiol Behav. 2005;85:354–362. doi: 10.1016/j.physbeh.2005.05.002. [DOI] [PubMed] [Google Scholar]
- 20.Newton SS, Collier EF, Hunsberger J, Adams D, Terwilliger R, Selvanayagam E, Duman RS. Gene profile of electroconvulsive seizures: Induction of neurotrophic and angiogenic factors. J Neurosci. 2003;23:10841–10851. doi: 10.1523/JNEUROSCI.23-34-10841.2003. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Warner-Schmidt JL, Duman RS. Hippocampal neurogenesis: Opposing effects of stress and antidepressant treatment. Hippocampus. 2006;16:239–249. doi: 10.1002/hipo.20156. [DOI] [PubMed] [Google Scholar]
- 22.Chen AC, Shirayama Y, Shin KH, Neve RL, Duman RS. Expression of the cAMP response element binding protein (CREB) in hippocampus produces an antidepressant effect. Biol Psychiatry. 2001;49:753–762. doi: 10.1016/s0006-3223(00)01114-8. [DOI] [PubMed] [Google Scholar]
- 23.Shirayama Y, Chen AC, Nakagawa S, Russell DS, Duman RS. Brain-derived neurotrophic factor produces antidepressant effects in behavioral models of depression. J Neurosci. 2002;22:3251–3261. doi: 10.1523/JNEUROSCI.22-08-03251.2002. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Koss WA, Gehlert DR, Shekhar A. Different effects of subchronic doses of 17-beta estradiol in two ethologically based models of anxiety utilizing female rats. Horm Behav. 2004;46:158–164. doi: 10.1016/j.yhbeh.2004.02.011. [DOI] [PubMed] [Google Scholar]
- 25.Ho YJ, Wang CF, Hsu Wy, Tseng T, Hsu CC, Kao MD, Tsai YF. Psychoimmunological effects of doscorea in ovariectomized rats: Role of anxiety level. Ann Gen Psychiatry. 2007;6:21–28. doi: 10.1186/1744-859X-6-21. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Barden N. Implication of the hypothalamic-pituitary-adrenal axis in the physiopathology of depression. J Psychiatry Neurosci. 2004;29:185–193. [PMC free article] [PubMed] [Google Scholar]
- 27.Newton SS, Duman RS. Regulation of neurogenesis and angiogenesis in depression. Curr Neurovasc Res. 2004;1:261–267. doi: 10.2174/1567202043362388. [DOI] [PubMed] [Google Scholar]
- 28.Karege F, Perroud N, Burkhardt S, Schwald M, Ballmann E, La Harpe R, Malafosse A. Alteration in kinase activity but not in protein levels of protein kinase B and glycogen synthase kinase-3beta in ventral prefrontal cortex of depressed suicide victims. Biol Psychiatry. 2007;61:240–245. doi: 10.1016/j.biopsych.2006.04.036. [DOI] [PubMed] [Google Scholar]
- 29.Merendino RA, Di Rosa AE, Di Pasquale G, Minciullo PL, Mangraviti C, Costantino A, et al. Interleukin-18 and CD30 serum levels in patients with moderate-severe depression. Mediators Inflamm. 2002;11:265–267. doi: 10.1080/096293502900000131. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 30.Porsolt RD, Bertin A, Blavet N, Deniel M, Jalfre M. Immobility induced by forced swimming in rats: Effects of agents which modify central catecholamine and serotonin activity. Eur J Pharmacol. 1979;57:201–210. doi: 10.1016/0014-2999(79)90366-2. [DOI] [PubMed] [Google Scholar]
- 31.Cannizzaro G, Flugy A, Cannizzaro C, Gagliano M, Sabatino M. Effects of desipramine and alprazolam in the forced swim test in rats after long-lasting termination of chronic exposure to picrotoxin and pentylenetetrazol. Eur Neuropsychopharmacol. 1993;3:477–484. doi: 10.1016/0924-977x(93)90272-n. [DOI] [PubMed] [Google Scholar]
- 32.Tezval H, Jahn O, Todorovic C, Sasse A, Eckart K, Spiess J. Cortagine, a specific agonist of the corticotrophin-releasing factor receptor subtype 1, is anxiogenic and antidepressive in the mouse model. Proc Natl Acad Sci U S A. 2004;101:9468–9473. doi: 10.1073/pnas.0403159101. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33.Nishimura H, Ida Y, Tsuda A, Tanaka M. Opposite effects of diazepam and b-CCE on immobility and straw-climbing behavior of rats in a modified forced swim test. Pharmacol Biochem Beh. 1989;33:227–231. doi: 10.1016/0091-3057(89)90454-1. [DOI] [PubMed] [Google Scholar]
- 34.Consoli D, Fedotova J, Micale V, Sapronov NS, Drago F. Stressors affect the response of male and female rats to clomipramine in a model of behavioral despair (forced swim test) Eur J Pharmacol. 2005;520:100–107. doi: 10.1016/j.ejphar.2005.08.012. [DOI] [PubMed] [Google Scholar]
- 35.Hendrick V, Altshuler L, Strouse T, Grosser S. Postpartum and nonpostpartum depression: Differences in presentation and response to pharmacologic treatment. Depress Anxiety. 2000;11:66–72. doi: 10.1002/(sici)1520-6394(2000)11:2<66::aid-da3>3.0.co;2-d. [DOI] [PubMed] [Google Scholar]
- 36.Smith SS, Gong QH, Li X, Moran MH, Bitran D, Frye CA, Hsu FC. Withdrawal from 3alpha-OH-5alpha-pregnan-20-One using a pseudo-pregnancy model alters the kinetics of hippocampal GABAA-gated current and increases the GABAA receptor alpha4 subunit in association with increased anxiety. J Neurosci. 1998;18:5275–5284. doi: 10.1523/JNEUROSCI.18-14-05275.1998. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 37.Bitran D, Shiekh M, McLeod M. Anxiolytic effect of progesterone is mediated by the neurosteroid allopregnanolone at brain GABAA receptors. J Neuroendocrinol. 1995;7:171–177. doi: 10.1111/j.1365-2826.1995.tb00744.x. [DOI] [PubMed] [Google Scholar]
- 38.Laconi MR, Casteller G, Gargiulo PA, Bregonzio C, Cabrera RJ. The anxiolytic effect of allopregnanolone is associated with gonadal hormonal status in female rats. Eur J Pharmacol. 2001;417:111–116. doi: 10.1016/s0014-2999(01)00865-2. [DOI] [PubMed] [Google Scholar]
- 39.Amin Z, Mason GF, Cavus I, Krystal JH, Rothman DL, Epperson CN. The interaction of neuroactive steroids and GABA in the development of neuropsychiatric disorders in women. Pharmacol Biochem Behav. 2006;84:635–643. doi: 10.1016/j.pbb.2006.06.007. [DOI] [PubMed] [Google Scholar]
- 40.Erskine MS, Barfield RJ, Goldman BD. Intraspecific fighting during late pregnancy and lactation in rats and effects of litter removal. Behav Biol. 1978;23:206–218. doi: 10.1016/s0091-6773(78)91814-x. [DOI] [PubMed] [Google Scholar]
- 41.Hansen S, Ferreira A. Food intake, aggression, and fear behavior in the mother rat: Control by neural systems concerned with milk ejection and maternal behavior. Behav Neurosci. 1986;100:64–70. doi: 10.1037//0735-7044.100.1.64. [DOI] [PubMed] [Google Scholar]
- 42.Rosenblatt JS, Factor E, Mayer AD. Relationship between maternal aggression and maternal care in the rat. Aggress Behav. 1994;20:243–255. [Google Scholar]
- 43.Ferreira A, Hansen S, Nielsen M, Archer T, Minor BG. Behavior of mother rats in conflict tests sensitive to anti-anxiety agents. Behav Neurosci. 1989;103:193–201. doi: 10.1037//0735-7044.103.1.193. [DOI] [PubMed] [Google Scholar]
- 44.Ferreira A, Pereira M, Agrati D, Uriarte N, Fernandez-Guasti A. Role of maternal behavior on aggression, fear and anxiety. Physiol Behav. 2002;77:197–204. doi: 10.1016/s0031-9384(02)00845-4. [DOI] [PubMed] [Google Scholar]
- 45.Hudmon A, Schulman H. Structure-function of the multifunctional Ca2+/calmodulin-dependent protein kinase II. Biochem J. 2002;364:593–611. doi: 10.1042/BJ20020228. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 46.Tighilet B, Hashikawa T, Jones EG. Cell- and lamina-specific expression and activity-dependent regulation of type II calcium/calmod-ulin-dependent protein kinase isoforms in monkey visual cortex. J Neurosci. 1998;18:2129–2146. doi: 10.1523/JNEUROSCI.18-06-02129.1998. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 47.Silva AJ, Paylor R, Wehner JM, Tonegawa S. Impaired spatial learning in alpha-calcium-calmodulin kinase II mutant mice. Science. 1992;257:206–211. doi: 10.1126/science.1321493. [DOI] [PubMed] [Google Scholar]
- 48.Bach ME, Hawkins RD, Osman M, Kandel ER, Mayford M. Impairment of spatial but not contextual memory in CaMKII mutant mice with a selective loss of hippocampal LTP in the range of the theta frequency. Cell. 1995;81:905–915. doi: 10.1016/0092-8674(95)90010-1. [DOI] [PubMed] [Google Scholar]
- 49.Mayford M, Bach ME, Huang YY, Wang L, Hawkins RD, Kandel ER. Control of memory formation through regulated expression of a CaMKII transgene. Science. 1996;274:1678–1683. doi: 10.1126/science.274.5293.1678. [DOI] [PubMed] [Google Scholar]
- 50.Frankland PW, O’Brien C, Ohno M, Kirkwood A, Silva AJ. Alpha-CaMKII-dependent plasticity in the cortex is required for permanent memory. Nature. 2001;411:309–313. doi: 10.1038/35077089. [DOI] [PubMed] [Google Scholar]
- 51.Popoli M, Vocaturo C, Perez J, Smeraldi E, Racagni G. Presynaptic Ca2+/calmodulin-dependent protein kinase II: Autophosphorylation and activity increase in the hippocampus after long-term blockade of serotonin reuptake. Mol Pharmacol. 1995;48:623–629. [PubMed] [Google Scholar]
- 52.Xing G, Russell S, Hough C, O’Grady J, Zhang L, Yang S, et al. Decreased prefrontal CaMKII alpha mRNA in bipolar illness. Neuroreport. 2002;13:501–505. doi: 10.1097/00001756-200203250-00029. [DOI] [PubMed] [Google Scholar]
- 53.Amada N, Aihara K, Ravid R, Horie M. Reduction of NR1 and phosphorylated Ca2+/calmodulin-dependent protein kinase II levels in Alzheimer’s disease. Neuroreport. 2005;16:1809–1813. doi: 10.1097/01.wnr.0000185015.44563.5d. [DOI] [PubMed] [Google Scholar]
- 54.Novak G, Seeman P, Tallerico T. Increased expression of calcium/ calmodulin-dependent protein kinase II beta in frontal cortex in schizophrenia and depression. Synapse. 2006;59:61–68. doi: 10.1002/syn.20211. [DOI] [PubMed] [Google Scholar]
- 55.Celano E, Tiraboschi E, Consogno E, D’Urso G, Mbakop MP, Gennarelli M, et al. Selective regulation of presynaptic calcium/calmodulin-dependent protein kinase II by psychotropic drugs. Biol Psychiatry. 2003;53:442–449. doi: 10.1016/s0006-3223(02)01491-9. [DOI] [PubMed] [Google Scholar]
- 56.Tiraboschi E, Giambelli R, D’Urso G, Galietta A, Barbon A, de Bartolomeis A, et al. Antidepressants activate CaMKII in neuron cell body by Thr286 phosphorylation. Neuroreport. 2004;15:2393–2396. doi: 10.1097/00001756-200410250-00018. [DOI] [PubMed] [Google Scholar]
- 57.Blakely RD, De Felice LJ, Hartzell HC. Molecular physiology of norepinephrine and serotonin transporters. J Exp Biol. 1994;196:263–281. doi: 10.1242/jeb.196.1.263. [DOI] [PubMed] [Google Scholar]
- 58.Frazer A. Antidepressants. J Clin Psychiatry. 1997;58:9–25. [PubMed] [Google Scholar]
- 59.Blakely RD, Ramamoorthy S, Schroeter S, Qian Y, Apparsundaram S, Galli A, DeFelice LJ. Regulated phosphorylation and trafficking of antidepressant-sensitive serotonin transporter proteins. Biol Psychiatry. 1998;44:169–178. doi: 10.1016/s0006-3223(98)00124-3. [DOI] [PubMed] [Google Scholar]
- 60.Ramamoorthy S, Samuvel DJ, Buck ER, Rudnick G, Jayanthi LD. Phosphorylation of threonine residue 276 is required for acute regulation of serotonin transporter by cyclic GMP. J Biol Chem. 2007;282:11639–11647. doi: 10.1074/jbc.M611353200. [DOI] [PubMed] [Google Scholar]
- 61.Djalali S, Holtje M, Grosse G, Rothe T, Stroh T, Grosse J, et al. Effects of brain-derived neurotrophic factor (BDNF) on glial cells and serotonergic neurones during development. J Neurochem. 2005;92:616–627. doi: 10.1111/j.1471-4159.2004.02911.x. [DOI] [PubMed] [Google Scholar]
- 62.Rubinow DR, Schimidt PJ, Roca CA. Estrogen-serotonin interactions: Implications for affective regulation. Biol Psychiatry. 1998;44:839–850. doi: 10.1016/s0006-3223(98)00162-0. [DOI] [PubMed] [Google Scholar]
- 63.Benmansour S, Owens WA, Cecchi M, Morilak DA, Frazer A. Serotonin clearance in vivo is altered to a greater extent by antidepressant-induced downregulation of the serotonin transporter than by acute blockade of this transporter. J Neurosci. 2002;22:6766–6772. doi: 10.1523/JNEUROSCI.22-15-06766.2002. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 64.Mao Z, Bonni A, Xia F, Nadal-Vicens M, Greenberg ME. Neuronal activity-dependent cell survival mediated by transcription factor MEF2. Science. 1999;286:785–790. doi: 10.1126/science.286.5440.785. [DOI] [PubMed] [Google Scholar]
- 65.Kalcheim C, Barde YA, Thoenen H, Le Douarin NM. In vivo effect of brain-derived neurotrophic factor on the survival of developing dorsal root ganglion cells. EMBO J. 1987;10:2871–2873. doi: 10.1002/j.1460-2075.1987.tb02589.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 66.Duman RS, Monteggia LM. A neurotrophic model for stress-related mood disorders. Biol Psychiatry. 2006;59:1116–1127. doi: 10.1016/j.biopsych.2006.02.013. [DOI] [PubMed] [Google Scholar]
- 67.Nibuya M, Morinobu S, Duman RS. Regulation of BDNF and trkB mRNA in rat brain by chronic electroconvulsive seizure and antidepressant drug treatments. J Neurosci. 1995;11:7539–7547. doi: 10.1523/JNEUROSCI.15-11-07539.1995. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 68.Hoshaw BA, Malberg JE, Lucki I. Central administration of IGF-I and BDNF leads to long-lasting antidepressant-like effects. Brain Res. 2005;1037:204–208. doi: 10.1016/j.brainres.2005.01.007. [DOI] [PubMed] [Google Scholar]
- 69.Hevers W, Luddens H. The diversity of GABAA receptors. Pharmacological and electrophysiological properties of GABAA channel sub-types. Mol Neurobiol. 1998;18:35–86. doi: 10.1007/BF02741459. [DOI] [PubMed] [Google Scholar]
- 70.Smith SS, Gong QH, Hsu FC, Markowitz RS, ffrench-Mullen JM, Li X. GABA(A) receptor alpha4 subunit suppression prevents withdrawal properties of an endogenous steroid. Nature. 1998;392:926–930. doi: 10.1038/31948. [DOI] [PubMed] [Google Scholar]
- 71.Badaut J, Lasbennes F, Magistretti PJ, Regli L. Aquaporins in brain: Distribution, physiology, and pathophysiology. J Cereb Blood Flow Metab. 2002;22:367–378. doi: 10.1097/00004647-200204000-00001. [DOI] [PubMed] [Google Scholar]
- 72.Iwamoto K, Kakiuchi C, Bundo M, Ikeda K, Kato T. Molecular characterization of bipolar disorder by comparing gene expression profiles of postmortem brains of major mental disorders. Mol Psychiatry. 2004;9:406–416. doi: 10.1038/sj.mp.4001437. [DOI] [PubMed] [Google Scholar]
- 73.Nakao A, Imamura T, Souchelnytskyi S, Kawabata M, Ishisaki A, Oeda E, et al. TGF-beta receptor-mediated signalling through Smad2, Smad3 and Smad4. EMBO J. 1997;16:5353–5362. doi: 10.1093/emboj/16.17.5353. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 74.Dow AL, Russell DS, Duman RS. Regulation of activin mRNA and Smad2 phosphorylation by antidepressant treatment in the rat brain: Effects in behavioral models. J Neurosci. 2005;25:4908–4916. doi: 10.1523/JNEUROSCI.5155-04.2005. [DOI] [PMC free article] [PubMed] [Google Scholar]
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