Skip to main content
NCBI home page
Endocrinology logoLink to Endocrinology
. 2008 Aug 7;149(12):6399–6405. doi: 10.1210/en.2008-0433

Organizational and Activational Effects of Testosterone on Masculinization of Female Physiological and Behavioral Stress Responses

Nirupa Goel 1, Tracy L Bale 1
PMCID: PMC2613052  PMID: 18687782

Abstract

The prevalence of affective disorders is two times greater in women than in men. The onset of anxiety and depression occurs at different ages that may correspond to key developmental periods when the brain is more vulnerable to hormonal and exogenous influences. Because stressful life events can precipitate disease onset, the development of greater stress sensitivity in females may contribute to their increased vulnerability. Gonadal hormone exposure in males during early development and again from puberty onward plays a prominent role in sexually dimorphic brain formation, possibly contributing to sex differences in stress responsivity. Therefore, organizational effects of testosterone propionate (TP) administered postnatally and activational effects of TP administered beginning at puberty on adult female physiological and behavioral stress responses were examined in mice. Although the activational effects of TP in females ameliorated the sex difference in the hypothalamic-pituitary-adrenal axis stress response, there was no effect of postnatal TP. Similarly, higher immobile time in intact females in the tail suspension test was blunted by activational TP in the absence of postnatal TP. However, in the marble-burying test of anxiety-like behaviors, organizational and activational TP independently resulted in increased burying behaviors. These results show that TP administration has distinct effects on reducing physiological and behavioral stress responsivity in rodent models and suggest that sex differences in these responses may partially result from the absence of testosterone in females.

THE LIFETIME prevalence of affective disorders including anxiety and major depression is nearly two times higher in women than in men (1). The presentation of behaviors associated with anxiety disorders begins to increase around age 5, whereas depression-related characteristics emerge around puberty (2), suggesting that divergent central mechanisms may underlie the timing of vulnerability to these disorders. One common factor in depression and anxiety etiology is dysregulation of stress neurocircuitry (3). The ability to respond appropriately and maintain homeostasis after stressors is an important factor in disease prevention.

Sex differences in the hypothalamic-pituitary-adrenal (HPA) axis stress response may play a role in the vulnerability to affective disorders. Adult female rodents display a greater physiological stress response than males as seen by higher corticosterone levels after a variety of stressors (4,5,6,7,8), regardless of estrous cycle stage (9,10). In females, basal and stress-induced corticosterone as well as hypothalamic corticotropin-releasing factor (CRF) expression are elevated during proestrous compared with diestrous or estrous (11,12,13). In addition, rodent studies have shown sex differences in behavioral responses to stress in which females use more passive strategies, such as increased immobile time in the forced swim and tail suspension tests compared with males (14,15,16). In humans, such passive responses have been associated with the occurrence of depressive symptoms (17,18).

Sex differences in the HPA axis in humans are more complex. In studies of healthy adults, men compared with women in the luteal phase of the menstrual cycle show similar plasma and salivary-free cortisol levels after stress, whereas free cortisol is lower in women during the follicular phase (19,20). Variability between studies showing either no sex differences in free cortisol or greater levels in men may be partially attributed to phase of the menstrual cycle (for review, see Ref. 21) or to the type of stress challenge. Plasma cortisol is higher in men in response to the Trier Social Stress Test and CRF stimulation but higher in women in response to naloxone and intense exercise (22,23,24). Interestingly, one study using stressors that are etiologically related to affective disorders showed that women responded to social rejection with greater salivary-free cortisol than men (25). Furthermore, depressed women exhibit greater ACTH secretion in the evening compared with depressed men (26,27). Thus, women may have a distinct type of HPA axis sensitivity that is related to the vulnerability to affective disorders.

Sex differences in physiological and behavioral stress responsivity may be related to differential brain development and/or modulation by gonadal hormones (28,29). Gonadal hormones can have effects that are organizational, which persist in the absence of circulating hormone, and activational, which require the presence of hormone. Testosterone exposure in males during both early brain formation and in puberty is critical for the development of the sexually dimorphic male brain, including masculinization of reproductive behavioral neurocircuitry (29,30). Some of these morphological effects can be reproduced in the female via a single testosterone injection on postnatal day (PN) 1 (31). Further sexually dimorphic brain development occurs during puberty, including greater enlargement of the amygdala in males and of the hippocampus in females (32,33). The brain regions with the greatest dimorphism in adulthood also have the highest expression of gonadal hormone receptors during critical periods of brain development (34), signifying the impact of early hormone organization on later activation.

The underlying mechanisms that contribute to the development of sex differences in stress responsivity have not been fully explored in rodent models. Therefore, we administered testosterone propionate (TP) to female mice on either PN 1 (organizational) and/or beginning at puberty (activational) and examined masculinization of physiological and behavioral stress responses compared with control male and female mice. We hypothesized that this masculinization would result in a reduced physiological stress response and increased active behaviors in adult females.

Materials and Methods

Animals

Twelve litters of 129:C57BL/6J mice were bred in our colony. On the day of birth, designated as PN 1, female pups were randomly assigned to one of four conditions shown in Table 1. Females assigned to determine organizational effects of TP (Sigma Life Science, St. Louis, MO) received 100 μg TP per pup sc in 20 μl sesame oil on PN 1 (abbreviated PN TP). This method has been shown to masculinize reproductive behavior in mice (35). Vehicle treatment (PN V) consisted of a 20-μl injection of sesame oil on PN 1. At 28 d, all mice were weaned and bilateral ovariectomy (OVX) surgery was performed on all female mice except for the intact group (♀PN V). Ovariectomy surgery was performed under isoflurane anesthesia immediately followed by implantation of a SILASTIC brand (Dow Corning, Midland, MI) capsule (inner diameter 1.98 mm, outer diameter 3.18 mm) that contained TP (3 mm TP; OVX TP) or was empty (OVX V). Implants were inserted sc, caudal to the scapula. The five experimental groups were as follows: 1) ♀PN V, ovary-intact females (n = 5), 2) ♀PN TP+OVX V (n = 10), 3) ♀PN V+OVX TP (n = 10), 4) ♀PN TP+OVX TP (n = 9), and 5) ♂PN V, intact males (n = 11). All mice were group housed under controlled conditions of a 12-h light, 12-h dark cycle with access to food and water ad libitum. In adulthood, females with intact ovaries (♀PN V) were cycled by taking vaginal smears. Cycle stage was determined using methods described previously (36). All procedures were approved by the Institutional Animal Care and Use Committee at the University of Pennsylvania.

Table 1.

Treatments and testing schedule

Birth sex (n) PN 1 PN 28 PN 67-78 PN 88-91
Female (5) V Behavioral testing HPA axis stress response
Female (10) TP OVX + V implant Behavioral testing HPA axis stress response
Female (10) V OVX + TP implant Behavioral testing HPA axis stress response
Female (9) TP OVX + TP implant Behavioral testing HPA axis stress response
Male (11) V Behavioral testing HPA axis stress response
Open in a new tab

Testosterone analysis

In a separate cohort of female mice (n = 6), plasma testosterone concentration resulting from SILASTIC brand implants was assessed. At 28 d, females were bilaterally OVX and given a TP-filled capsule as described above. Blood samples were collected at d 70, 77, and 91. These time points coordinate with behavior and HPA axis testing used in these studies. Samples were assayed using a commercial 125I RIA kit for total testosterone (Diagnostic Products Corp., Los Angeles, CA). The minimum detection limit of the assay was 4 ng/dl, and intraassay coefficient of variation was 17%. Data were converted to nanograms per milliliter in Table 2.

Table 2.

Plasma testosterone concentrations resulting from a TP implant

Age (d) Plasma testosterone (ng/ml)
70 3.9 ± 0.7
77 3.5 ± 0.5
91 2.8 ± 0.6
Open in a new tab

Corticosterone analysis

The HPA axis response to acute stress was measured by exposing mice to a 15-min restraint in a 50-ml conical tube (37). Testing occurred between 2 and 5 h after lights on and was performed on mice between the ages of PN 88 and 91. Blood samples were collected from a tail nick at four time points: 1) time 0, immediately upon removal from the cage, 2) time 15, immediately after the restraint stress, 3) time 30, after 15 min recovery in the home cage, and 4) time 90, after 75 min recovery in the home cage. Samples were collected into EDTA-treated tubes, immediately centrifuged, and stored at −80 C until assayed for corticosterone. Corticosterone concentrations were measured using a commercial 125I RIA kit (MP Biomedicals, Orangeburg, NY). The minimum detection limit of the assay was 7.7 ng/ml, and intraassay coefficient of variation was 7.3%.

Behavior testing

Testing occurred from PN 67-78. Behavior tests were chosen based on previously reported sex differences and were conducted in the following order with 2 d rest between each test.

Tail suspension test.

To measure depression-like behaviors in a stress-provoking task, we performed the tail suspension test. Testing was performed as previously described (38). Distance from floor was 40 cm. Testing occurred during the light cycle for a duration of 6 min. Testing was digitally recorded and analyzed using ANY-maze software (Stoelting Co., Wood Dale, IL).

Marble-burying test.

To measure stress-provoked anxiety-like responses, we performed the marble-burying test (37). Mice were placed individually in cages (20 × 40 × 15 cm) with 5 cm bedding and 12 uniform marbles evenly distributed on the surface of the bedding. Testing occurred in the dark phase of the light/dark cycle for a duration of 30 min. An overhead lamp was used to illuminate the testing room at 100 lux. The number of marbles buried (two thirds covered by bedding) was binned at 5-min intervals.

Light-dark box.

To further measure anxiety-like responses, light-dark box testing was performed as previously described (39). Light intensity was 5 lux in the dark compartment and 300 lux in the light compartment. Test duration was 10 min. Testing occurred 2 h into the dark cycle. Behaviors were scored using ANY-maze software.

Statistical analysis

Corticosterone and marble-burying data were analyzed using repeated-measures ANOVA (time × group). Additionally, corticosterone was analyzed for rate of HPA axis activation by performing a one-way ANOVA on the slope of corticosterone from 0–15 min. All other data were analyzed using one-way ANOVA. Significant differences were identified at P < 0.05. To reveal specific differences between groups, significant main effects and interactions were further analyzed with Student’s t test. All data are reported as mean ± sem.

Results

Plasma testosterone

Plasma testosterone resulting from TP implants was measured in a separate group of female mice on PN 70, 77, and 91, corresponding to the timing of behavioral and HPA axis testing. Values were in the range of an intact male mouse during these tests (Table 2) (40,41,42).

HPA axis stress response

To examine the contribution of organizational and activational effects of testosterone on masculinization of the HPA stress axis response, corticosterone levels were measured after a 15-min restraint stress (Fig. 1). A significant main effect of group and a significant group × time interaction [F(4,27) = 22.28 and F(4,27) = 18.41; P < 0.0001 for both] was revealed by repeated-measures ANOVA. Due to the interaction, individual time points were analyzed for main effects of group. We analyzed the peak response at time 30 and found a main effect of group [F(4,32) = 10.68; P < 0.0001]. Post hoc analysis revealed that intact females showed greater peak response than males and postnatally masculinized females showed a feminized response, whereas corticosterone levels were significantly reduced by activational effects of TP (PN V and PN TP+OVX V were different from males, PN V+OVX TP, and PN TP+OVX TP; P < 0.05 for time 30). During recovery at time 90, a main effect of group [F(4,31) = 22.51; P < 0.0001] was further analyzed to reveal a difference between the PN TP+OVX V mice and all others (P < 0.05). Intact females and males displayed similar recovery corticosterone levels at 90 min. In addition, rate of HPA axis activation was assessed by analysis of slope from 0–15. We found a main effect of group [F(4,33) = 11.60; P < 0.0001] and post hoc analysis showed that intact females and postnatally masculinized females showed a greater initial corticosterone rise than males and females with activational TP (PN V and PN TP+OVX V were different from males, PN V+OVX TP, and PN TP+OVX TP; P < 0.05).

Figure 1.

Figure 1

Open in a new tab

Sex differences in corticosterone levels after a 15-min restraint stress are reduced in females by activational effects of TP. Intact females exhibited an elevated corticosterone rise and peak value compared with males. Activational effects of TP in females resulted in a masculinized response, whereas postnatal TP exposure did not change this response (main effect of group, P < 0.0001; group × time interaction, P < 0.0001; * and #, P < 0.05 post hoc tests for slope from 0–15 and for time 30, respectively). At time 90, recovery was delayed in the ♀PN TP+OVX V group (main effect of group, P < 0.0001; #, P < 0.05 post hoc test showing difference from all other groups). V, Vehicle.

Tail suspension test

To examine the effects of organizational vs. activational TP administration in a test of antidepressant efficacy, we performed the tail suspension test. Analysis of immobile time in the tail suspension test revealed a main effect of group [F(4,37) = 5.50; P < 0.01; Fig. 2]. Post hoc testing showed a sex difference that was masculinized by activational TP exposure in the absence of PN TP. Specifically, intact females and the two groups with postnatal testosterone (PN TP+OVX V and PN TP+OVX TP) displayed greater time spent immobile than males (P < 0.05). Additionally, the PN V+OVX TP mice, showing immobile time similar to males, were significantly different from the two postnatally treated groups (P < 0.05).

Figure 2.

Figure 2

Open in a new tab

Activational TP treatment in the absence of postnatal TP masculinized immobile time in the tail suspension test. There were significant differences in time spent immobile among the groups (main effect of group, P < 0.01). Post hoc analysis revealed that intact females and females with postnatal TP treatment showed greater immobility than males (*, P < 0.05). Immobility was reduced in females with only activational TP exposure (#, P < 0.05). V, Vehicle.

Marble-burying test

To examine sex differences in active behaviors related to anxiety and the effects of masculinization, we performed the marble-burying test (Fig. 3). Data were collected in 5-min bins for 30 min, and marbles buried were analyzed by repeated-measures ANOVA. A trend was found for intact females to bury fewer marbles than males [F(1,12) = 4.05; P = 0.07 by repeated-measures ANOVA]. Either organizational or activational TP increased burying, as found by comparing intact females with all treatment groups and intact males [F(1,39) = 4.20; P < 0.05 by repeated-measures ANOVA].

Figure 3.

Figure 3

Open in a new tab

Either organizational or activational TP exposure masculinized active burying behavior in females in the marble-burying test. Intact females buried fewer marbles compared with males and females treated with organizational or activational TP (*, P < 0.05, intact females compared with all other groups by repeated-measures ANOVA). V, Vehicle.

Light-dark box

To examine anxiety-like behaviors, we measured responses in the light-dark box. There were no significant effects of TP on time spent in the light compartment or the average bout in the dark compartment [F(4,38) = 0.95, P = 0.45 and F(4,37) = 0.23, P = 0.92; Fig. 4, A and B]. Locomotion, as measured by total number of transitions between compartments, was not significantly altered by TP administration [F(4,37) = 0.31; P = 0.87; Fig. 4C].

Figure 4.

Figure 4

Open in a new tab

Effects of TP exposure in females on anxiety-like behaviors in the light-dark box. A and B, There were no significant differences in time spent in the light compartment (A) or the average bout in the dark (B). C, TP treatment did not affect number of transitions between compartments. V, Vehicle.

Discussion

In comparison with males, female rodents exhibit greater physiological and behavioral stress sensitivity. Gonadal hormones are influential in early brain development through organizational effects as well as in modulation of adult physiology and behavior through activational effects. Testosterone plays an important role in suppressing the HPA stress axis and in increasing active behavioral responses to environmental challenges in males (4,43,44), contributing to sex differences in stress responsivity. We sought to examine whether female physiological and behavioral stress responses could be masculinized by organizational and/or activational effects of testosterone by administration of TP as a single injection on PN 1 or as a sc implant beginning at puberty.

As a measure of HPA axis stress physiology, we examined a time course of corticosterone levels after an acute restraint stress. As expected, we detected a sex difference in corticosterone between intact males and females where females showed a substantially higher maximal rise after the restraint. We found that activational effects of TP in females resulted in significantly decreased corticosterone to levels similar to males. This effect was observed in the presence or absence of postnatal treatment. Surprisingly, the females treated with only postnatal TP were not masculinized, still displaying an elevated corticosterone response compared with males. These results differ from those previously reported showing that female rats treated with testosterone on PN 1 display a reduced corticosterone response after 10 min of white noise stress (45). These findings may support species differences in the development of the HPA stress axis or may be related to differences in methodology, including type of stressor used. Interestingly, the postnatal TP-treated females displayed a slower stress recovery than other treatment groups, suggestive of altered negative feedback that may relate to changes in glucocorticoid receptor levels or limbic system development. We have previously shown that early expression of heightened HPA axis responsivity can be a predictor of adult stress sensitivity (37). Our results show that the presence of activational testosterone has a greater influence than early organizational effects on masculinizing the physiological stress response. Moreover, human studies have shown that testosterone administration in females results in decreased stress responsivity measured by skin conductance and startle behavior (46). In addition, in men, testosterone replacement after gonadal suppression resulted in decreased CRF-stimulated cortisol and cortisol to ACTH ratio (47). Thus, similar to our rodent studies, activational testosterone leads to decreased stress responsivity in humans, too.

A masculinization of the stress response is likely the result of modulatory actions of testosterone on the HPA axis (4,5,48). These effects may involve multiple mechanisms, including decreasing cellular activation in the hypothalamus after stress exposure, decreasing CRF expression, and increasing glucocorticoid receptor expression to promote negative feedback (4,5,49,50). Possible additional sex differences involved in the HPA stress axis include females exhibiting greater adrenal gland weight, adrenal zona fasciculata volume, and CRF-binding protein expression in the pituitary (51,52,53). Whether these differences can be masculinized by testosterone exposure or have an influence on HPA stress axis function have not yet been investigated.

Behavioral stress responses were also examined to assess the organizational and activational effects of TP in female mice. The behavioral tests were selected for their predictive sex differences where females typically show more passive responses than males (15,16,54,55). In humans, passive coping is more prevalent in females and is associated with higher depressive scores (17,18). Estrous cycle stage of intact female mice was monitored on each day of testing. Variability in behaviors in this group may be attributed to differences in cycle stage. In the tail suspension test, intact females showed greater immobile time than males. Activational effects of TP in the absence of postnatal TP reduced female time spent immobile, resulting in a masculinized response. These data are in agreement with previous work showing that after gonadectomy, TP replacement in males reduces immobile time in this test (43). Postnatal TP treatment did not result in a change in immobile time, and surprisingly, mice exposed to both organizational and activational TP were not masculinized in their behavior as we had expected. The lack of activational TP effects in this female group compared with the known effect in males points to a likely influence of sex chromosomes. Previous studies have shown that genetic sex, independent from gonadal sex and hormonal condition, is an important determining factor in adult behavior and in brain development (56,57,58). For example, testosterone exposure during development is responsible for the larger volume of the sexually dimorphic nucleus of the preoptic area in males. Males and females that are gonadectomized and ovariectomized on PN 1 and given a testosterone injection show increased volume of this nucleus, but the magnitude of the effect is greater in males than females (31). This may lead to an altered response in females to later exposure. Although precise mechanisms are unknown, our data suggest that PN 1 testosterone exposure may have differing effects on dimorphic brain regions in males and females, thereby altering later hormone responses.

Anxiety-like behavioral responses were also compared in these mice. In the marble-burying test, intact females displayed the lowest burying behavior, indicative of predicted passive stress behavioral responses. Previous studies have also shown that females are less active in defensive burying tasks (55). Females treated with either organizational or activational TP and males were significantly different from intact females in that they buried a greater number of marbles. The effect of activational TP to increase burying duration has been previously demonstrated in gonadectomized male rats (59). Our studies show similar results in female mice, in addition to showing effects of organizational TP to increase active coping. In a separate anxiety-like task, the light-dark box, there were no sex differences or significant effects of TP on time spent in the light side of the box or locomotor performance as measured by transitions between light and dark compartments. The differential results from these two tests may be due to the types of anxiety-provoking stimuli presented. In the marble-burying test, the stimuli are novel objects that the mice must actively bury while being unable to escape the environment. In contrast, in the light-dark box, mice have a choice of two environments and can easily avoid the bright, open compartment. Behaviors in these two tests represent different styles of coping. Females have been previously reported to spend less time in the light compartment than males, indicative of an increased anxiety-like response in this test (54). However, the reported study used a different strain and age of mice and a shorter test duration, which are important variables in rodent behavior testing. Moreover, in agreement with our results, studies of the effects of testosterone on behavior in the light-dark box have not shown significant changes in male rats (60,61). In other anxiety-like tasks, including the open-field test and the elevated plus maze, testosterone and its nonaromatizable metabolites have been shown to increase center time and open arm time, respectively (44,62). This suggests that behaviors in these anxiety-like tests may be more sensitive to the effects of testosterone, possibly due to the slight differences in stimuli that these tests present vs. the light-dark box. The elevated plus maze is conducted during the light cycle in very low light conditions, and the open-field test, like the marble-burying test, does not provide an escape. In summary, our data demonstrate that normally passive female coping behaviors in the marble-burying test can be masculinized by organizational or activational effects of TP, whereas in the tail suspension test, only activational TP masculinized the behavioral response. The difference in results from anxiety- and depression-like tasks suggests that organizational and activational TP have unique profiles of behavioral effects.

Overall, testosterone exposure appears to be a major contributor to sex differences in physiological and behavioral stress responsivity. The mechanisms by which testosterone produces these effects may occur through changes in dendritic morphology and gene expression in stress-responsive brain areas (5,63,64). Our studies suggest that testosterone may act on different neurobiological targets depending on whether the exposure was organizational or activational. Early postnatal life is a sensitive period during which hormone exposure can have organizational effects that alter serotonin system maturation (65), potentially leading to long-term changes in stress sensitivity. The presence of testosterone in adulthood may exert further modulatory effects on serotonin and γ-aminobutyric acid systems (62,66), thereby affecting active behaviors and stress physiology. Puberty is thought to be a second window of organizational effects by gonadal hormones (67). In our studies, activational TP exposure began at puberty onset. Thus, future studies will limit TP exposure to occur only during puberty to more specifically delineate activational vs. organizational effects during this window on stress responses.

Acknowledgments

We thank Yanming Xiong for her assistance.

Footnotes

This work was supported by National Institutes of Health Grant MH073030.

Disclosure Statement: The authors have nothing to disclose.

First Published Online August 7, 2008

Abbreviations: CRF, Corticotropin-releasing factor; HPA, hypothalamic-pituitary-adrenal; OVX, ovariectomized; PN, postnatal day; TP, testosterone propionate; V, vehicle.

References

  1. Kessler RC, McGonagle KA, Zhao S, Nelson CB, Hughes M, Eshleman S, Wittchen HU, Kendler KS 1994 Lifetime and 12-month prevalence of DSM-III-R psychiatric disorders in the United States. Results from the National Comorbidity Survey. Arch Gen Psychiatry 51:8–19 [DOI] [PubMed] [Google Scholar]
  2. Roza SJ, Hofstra MB, van der Ende J, Verhulst FC 2003 Stable prediction of mood and anxiety disorders based on behavioral and emotional problems in childhood: a 14-year follow-up during childhood, adolescence, and young adulthood. Am J Psychiatry 160:2116–2121 [DOI] [PubMed] [Google Scholar]
  3. Arborelius L, Owens MJ, Plotsky PM, Nemeroff CB 1999 The role of corticotropin-releasing factor in depression and anxiety disorders. J Endocrinol 160:1–12 [DOI] [PubMed] [Google Scholar]
  4. Handa RJ, Burgess LH, Kerr JE, O'Keefe JA 1994 Gonadal steroid hormone receptors and sex differences in the hypothalamo-pituitary-adrenal axis. Horm Behav 28:464–476 [DOI] [PubMed] [Google Scholar]
  5. Seale JV, Wood SA, Atkinson HC, Harbuz MS, Lightman SL 2004 Gonadal steroid replacement reverses gonadectomy-induced changes in the corticosterone pulse profile and stress-induced hypothalamic-pituitary-adrenal axis activity of male and female rats. J Neuroendocrinol 16:989–998 [DOI] [PubMed] [Google Scholar]
  6. Young EA 1996 Sex differences in response to exogenous corticosterone: a rat model of hypercortisolemia. Mol Psychiatry 1:313–319 [PubMed] [Google Scholar]
  7. Frederic F, Oliver C, Wollman E, Bouchaud ND, Mariani J 1993 IL-1 and LPS induce a sexually dimorphic response of the hypothalamo-pituitary-adrenal axis in several mouse strains. Eur Cytokine Netw 4:321–329 [PubMed] [Google Scholar]
  8. Harizi H, Delarche FH, Amrani A, Coulaud J, MormËde P 2007 Marked genetic differences in the regulation of blood glucose under immune and restraint stress in mice reveals a wide range of corticosensitivity. J Neuroimmunol 189:59–68 [DOI] [PubMed] [Google Scholar]
  9. Rhodes ME, Kennell JS, Belz EE, Czambel RK, Rubin RT 2004 Rat estrous cycle influences the sexual diergism of HPA axis stimulation by nicotine. Brain Res Bull 64:205–213 [DOI] [PubMed] [Google Scholar]
  10. Spinedi E, Suescun MO, Hadid R, Daneva T, Gaillard RC 1992 Effects of gonadectomy and sex hormone therapy on the endotoxin-stimulated hypothalamo-pituitary-adrenal axis: evidence for a neuroendocrine-immunological sexual dimorphism. Endocrinology 131:2430–2436 [DOI] [PubMed] [Google Scholar]
  11. Bohler HC, Zoeller RT, King JC, Rubin BS, Weber R, Merriam GR 1990 Corticotropin releasing hormone mRNA is elevated on the afternoon of proestrus in the parvocellular paraventricular nuclei of the female rat. Brain Res Mol Brain Res 8:259–262 [DOI] [PubMed] [Google Scholar]
  12. Nichols DJ, Chevins PF 1981 Plasma corticosterone fluctuations during the oestrous cycle of the house mouse. Experientia 37:319–320 [DOI] [PubMed] [Google Scholar]
  13. Viau V, Meaney MJ 1991 Variations in the hypothalamic-pituitary-adrenal response to stress during the estrous cycle in the rat. Endocrinology 129:2503–2511 [DOI] [PubMed] [Google Scholar]
  14. Bale TL, Vale WW 2003 Increased depression-like behaviors in corticotropin-releasing factor receptor-2-deficient mice: sexually dichotomous responses. J Neurosci 23:5295–5301 [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Liu X, Gershenfeld HK 2001 Genetic differences in the tail-suspension test and its relationship to imipramine response among 11 inbred strains of mice. Biol Psychiatry 49:575–581 [DOI] [PubMed] [Google Scholar]
  16. Pelloux Y, Hagues G, Costentin J, Duterte-Boucher D 2005 Helplessness in the tail suspension test is associated with an increase in ethanol intake and its rewarding effect in female mice. Alcohol Clin Exp Res 29:378–388 [DOI] [PubMed] [Google Scholar]
  17. Hanninen V, Aro H 1996 Sex differences in coping and depression among young adults. Soc Sci Med 43:1453–1460 [DOI] [PubMed] [Google Scholar]
  18. Kaya M, Genc M, Kaya B, Pehlivan E 2007 [Prevalence of depressive symptoms, ways of coping, and related factors among medical school and health services higher education students]. Turk Psikiyatri Derg 18:137–146 (Turkish) [PubMed] [Google Scholar]
  19. Kirschbaum C, Kudielka BM, Gaab J, Schommer NC, Hellhammer DH 1999 Impact of gender, menstrual cycle phase, and oral contraceptives on the activity of the hypothalamus-pituitary-adrenal axis. Psychosom Med 61:154–162 [DOI] [PubMed] [Google Scholar]
  20. Rohleder N, Schommer NC, Hellhammer DH, Engel R, Kirschbaum C 2001 Sex differences in glucocorticoid sensitivity of proinflammatory cytokine production after psychosocial stress. Psychosom Med 63:966–972 [DOI] [PubMed] [Google Scholar]
  21. Kajantie E, Phillips DIW 2006 The effects of sex and hormonal status on the physiological response to acute psychosocial stress. Psychoneuroendocrinology 31:151–178 [DOI] [PubMed] [Google Scholar]
  22. Deuster PA, Petrides JS, Singh A, Lucci EB, Chrousos GP, Gold PW 1998 High intensity exercise promotes escape of adrenocorticotropin and cortisol from suppression by dexamethasone: sexually dimorphic responses. J Clin Endocrinol Metab 83:3332–3338 [DOI] [PubMed] [Google Scholar]
  23. Uhart M, Chong RY, Oswald L, Lin PI, Wand GS 2006 Gender differences in hypothalamic-pituitary-adrenal (HPA) axis reactivity. Psychoneuroendocrinology 31:642–652 [DOI] [PubMed] [Google Scholar]
  24. Roca CA, Schmidt PJ, Deuster PA, Danaceau MA, Altemus M, Putnam K, Chrousos GP, Nieman LK, Rubinow DR 2005 Sex-related differences in stimulated hypothalamic-pituitary-adrenal axis during induced gonadal suppression. J Clin Endocrinol Metab [Erratum (2005) 90:5522] 90:4224–4231 [DOI] [PubMed] [Google Scholar]
  25. Stroud LR, Salovey P, Epel ES 2002 Sex differences in stress responses: social rejection versus achievement stress. Biol Psychiatry 52:318–327 [DOI] [PubMed] [Google Scholar]
  26. Young EA, Ribeiro SC 2006 Sex differences in the ACTH response to 24H metyrapone in depression. Brain Res 1126:148–155 [DOI] [PubMed] [Google Scholar]
  27. Young EA, Ribeiro SC, Ye W 2007 Sex differences in ACTH pulsatility following metyrapone blockade in patients with major depression. Psychoneuroendocrinology 32:503–507 [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Arnold AP, Gorski RA 1984 Gonadal steroid induction of structural sex differences in the central nervous system. Annu Rev Neurosci 7:413–442 [DOI] [PubMed] [Google Scholar]
  29. MacLusky NJ, Naftolin F 1981 Sexual differentiation of the central nervous system. Science 211:1294–1302 [DOI] [PubMed] [Google Scholar]
  30. Feder HH, Phoenix CH, Young WC 1966 Suppression of feminine behaviour by administration of testosterone propionate to neonatal rats. J Endocrinol 34:131–132 [DOI] [PubMed] [Google Scholar]
  31. Jacobson CD, Csernus VJ, Shryne JE, Gorski RA 1981 The influence of gonadectomy, androgen exposure, or a gonadal graft in the neonatal rat on the volume of the sexually dimorphic nucleus of the preoptic area. J Neurosci 1:1142–1147 [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Giedd JN, Castellanos FX, Rajapakse JC, Vaituzis AC, Rapoport JL 1997 Sexual dimorphism of the developing human brain. Prog Neuropsychopharmacol Biol Psychiatry 21:1185–1201 [DOI] [PubMed] [Google Scholar]
  33. Koshibu K, Levitt P, Ahrens ET 2004 Sex-specific, postpuberty changes in mouse brain structures revealed by three-dimensional magnetic resonance microscopy. Neuroimage 22:1636–1645 [DOI] [PubMed] [Google Scholar]
  34. Goldstein JM, Seidman LJ, Horton NJ, Makris N, Kennedy DN, Caviness VS, Faraone SV, Tsuang MT 2001 Normal sexual dimorphism of the adult human brain assessed by in vivo magnetic resonance imaging. Cereb Cortex 11:490–497 [DOI] [PubMed] [Google Scholar]
  35. Manning A, McGill TE 1974 Neonatal androgen and sexual behavior in female house mice. Horm Behav 5:19–31 [DOI] [PubMed] [Google Scholar]
  36. Nelson JF, Felicio LS, Randall PK, Sims C, Finch CE 1982 A longitudinal study of estrous cyclicity in aging C57BL/6J mice. I. Cycle frequency, length and vaginal cytology. Biol Reprod 27:327–339 [DOI] [PubMed] [Google Scholar]
  37. Goel N, Bale TL 2007 Identifying early behavioral and molecular markers of future stress sensitivity. Endocrinology 148:4585–4591 [DOI] [PubMed] [Google Scholar]
  38. Steru L, Chermat R, Thierry B, Simon P 1985 The tail suspension test: a new method for screening antidepressants in mice. Psychopharmacology (Berl) 85:367–370 [DOI] [PubMed] [Google Scholar]
  39. Bale TL, Contarino A, Smith GW, Chan R, Gold LH, Sawchenko PE, Koob GF, Vale WW, Lee KF 2000 Mice deficient for corticotropin-releasing hormone receptor-2 display anxiety-like behaviour and are hypersensitive to stress. Nat Genet 24:410–414 [DOI] [PubMed] [Google Scholar]
  40. Al-Attar L, Noel K, Dutertre M, Belville C, Forest MG, Burgoyne PS, Josso N, Rey R 1997 Hormonal and cellular regulation of Sertoli cell anti-Mullerian hormone production in the postnatal mouse. J Clin Invest 100:1335–1343 [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Krishnamurthy H, Babu PS, Morales CR, Sairam MR 2001 Delay in sexual maturity of the follicle-stimulating hormone receptor knockout male mouse. Biol Reprod 65:522–531 [DOI] [PubMed] [Google Scholar]
  42. Machida T, Yonezawa Y, Noumura T 1981 Age-associated changes in plasma testosterone levels in male mice and their relation to social dominance or subordinance. Horm Behav 15:238–245 [DOI] [PubMed] [Google Scholar]
  43. Bernardi M, Genedani S, Tagliavini S, Bertolini A 1989 Effect of castration and testosterone in experimental models of depression in mice. Behav Neurosci 103:1148–1150 [DOI] [PubMed] [Google Scholar]
  44. Edinger KL, Frye CA 2005 Testosterone’s anti-anxiety and analgesic effects may be due in part to actions of its 5α-reduced metabolites in the hippocampus. Psychoneuroendocrinology 30:418–430 [DOI] [PubMed] [Google Scholar]
  45. Seale JV, Wood SA, Atkinson HC, Harbuz MS, Lightman SL 2005 Postnatal masculinization alters the HPA axis phenotype in the adult female rat. J Physiol 563:265–274 [DOI] [PMC free article] [PubMed] [Google Scholar]
  46. Hermans EJ, Putman P, Baas JM, Gecks NM, Kenemans JL, van Honk J 2007 Exogenous testosterone attenuates the integrated central stress response in healthy young women. Psychoneuroendocrinology 32:1052–1061 [DOI] [PubMed] [Google Scholar]
  47. Rubinow DR, Roca CA, Schmidt PJ, Danaceau MA, Putnam K, Cizza G, Chrousos G, Nieman L 2005 Testosterone suppression of CRH-stimulated cortisol in men. Neuropsychopharmacology 30:1906–1912 [DOI] [PMC free article] [PubMed] [Google Scholar]
  48. Viau V, Meaney MJ 1996 The inhibitory effect of testosterone on hypothalamic-pituitary-adrenal responses to stress is mediated by the medial preoptic area. J Neurosci 16:1866–1876 [DOI] [PMC free article] [PubMed] [Google Scholar]
  49. Bingaman EW, Magnuson DJ, Gray TS, Handa RJ 1994 Androgen inhibits the increases in hypothalamic corticotropin-releasing hormone (CRH) and CRH-immunoreactivity following gonadectomy. Neuroendocrinology 59:228–234 [DOI] [PubMed] [Google Scholar]
  50. Lund TD, Munson DJ, Haldy ME, Handa RJ 2004 Androgen inhibits, while oestrogen enhances, restraint-induced activation of neuropeptide neurones in the paraventricular nucleus of the hypothalamus. J Neuroendocrinol 16:272–278 [DOI] [PubMed] [Google Scholar]
  51. Bielohuby M, Herbach N, Wanke RD, Maser-Gluth C, Beuschlein F, Wolf E, Hoeflich A 2007 Growth analysis of the mouse adrenal gland from weaning to adulthood: time- and gender-dependent alterations of cell size and number in the cortical compartment. Am J Physiol Endocrinol Metab 293:E139–E146 [DOI] [PubMed] [Google Scholar]
  52. Majchrzak M, Malendowicz LK 1983 Sex differences in adrenocortical structure and function. XII. Stereologic studies of rat adrenal cortex in the course of maturation. Cell Tissue Res 232:457–469 [DOI] [PubMed] [Google Scholar]
  53. Speert DB, McClennen SJ, Seasholtz AF 2002 Sexually dimorphic expression of corticotropin-releasing hormone-binding protein in the mouse pituitary. Endocrinology 143:4730–4741 [DOI] [PubMed] [Google Scholar]
  54. Guo M, Wu CF, Liu W, Yang JY, Chen D 2004 Sex difference in psychological behavior changes induced by long-term social isolation in mice. Prog Neuropsychopharmacol Biol Psychiatry 28:115–121 [DOI] [PubMed] [Google Scholar]
  55. Wilson MA, Burghardt PR, Ford KA, Wilkinson MB, Primeaux SD 2004 Anxiolytic effects of diazepam and ethanol in two behavioral models: comparison of males and females. Pharmacol Biochem Behav 78:445–458 [DOI] [PubMed] [Google Scholar]
  56. Carruth LL, Reisert I, Arnold AP 2002 Sex chromosome genes directly affect brain sexual differentiation. Nat Neurosci 5:933–934 [DOI] [PubMed] [Google Scholar]
  57. Gatewood JD, Wills A, Shetty S, Xu J, Arnold AP, Burgoyne PS, Rissman EF 2006 Sex chromosome complement and gonadal sex influence aggressive and parental behaviors in mice. J Neurosci 26:2335–2342 [DOI] [PMC free article] [PubMed] [Google Scholar]
  58. Quinn JJ, Hitchcott PK, Umeda EA, Arnold AP, Taylor JR 2007 Sex chromosome complement regulates habit formation. Nat Neurosci 10:1398–1400 [DOI] [PubMed] [Google Scholar]
  59. Edinger KL, Frye CA 2006 Intrahippocampal administration of an androgen receptor antagonist, flutamide, can increase anxiety-like behavior in intact and DHT-replaced male rats. Horm Behav 50:216–222 [DOI] [PubMed] [Google Scholar]
  60. Edinger KL, Frye CA 2007 Sexual experience of male rats influences anxiety-like behavior and androgen levels. Physiol Behav 92:443–453 [DOI] [PubMed] [Google Scholar]
  61. Frye CA, Edinger K, Sumida K 2008 Androgen administration to aged male mice increases anti-anxiety behavior and enhances cognitive performance. Neuropsychopharmacology 33:1049–1061 [DOI] [PMC free article] [PubMed] [Google Scholar]
  62. Bitran D, Kellogg CK, Hilvers RJ 1993 Treatment with an anabolic-androgenic steroid affects anxiety-related behavior and alters the sensitivity of cortical GABAA receptors in the rat. Horm Behav 27:568–583 [DOI] [PubMed] [Google Scholar]
  63. Cooke BM, Woolley CS 2005 Gonadal hormone modulation of dendrites in the mammalian CNS. J Neurobiol 64:34–46 [DOI] [PubMed] [Google Scholar]
  64. Romeo RD, Staub D, Jasnow AM, Karatsoreos IN, Thornton JE, McEwen BS 2005 Dihydrotestosterone increases hippocampal N-methyl-d-aspartate binding but does not affect choline acetyltransferase cell number in the forebrain or choline transporter levels in the CA1 region of adult male rats. Endocrinology 146:2091–2097 [DOI] [PubMed] [Google Scholar]
  65. Dominguez R, Cruz-Morales SE, Carvalho MC, Xavier M, Brandao ML 2003 Effect of steroid injection to newborn rats on serotonin activity in frontal cortex and raphe. Neuroreport 14:597–599 [DOI] [PubMed] [Google Scholar]
  66. Robichaud M, Debonnel G 2005 Oestrogen and testosterone modulate the firing activity of dorsal raphe nucleus serotonergic neurones in both male and female rats. J Neuroendocrinol 17:179–185 [DOI] [PubMed] [Google Scholar]
  67. Sisk CL, Zehr JL 2005 Pubertal hormones organize the adolescent brain and behavior. Front Neuroendocrinol 26:163–174 [DOI] [PubMed] [Google Scholar]

Articles from Endocrinology are provided here courtesy of The Endocrine Society

RESOURCES