Skip to main content
NCBI home page
NIHPA Author Manuscripts logoLink to NIHPA Author Manuscripts
. Author manuscript; available in PMC: 2021 Nov 1.
Published in final edited form as: Horm Behav. 2020 Sep 18;126:104851. doi: 10.1016/j.yhbeh.2020.104851

Brain region-dependent alterations in polysialic acid immunoreactivity across the estrous cycle in mice

Laura L Giacometti 1, Fangyi Huang 1, Brianna S Hamilton 1, Jacqueline M Barker 1
PMCID: PMC7725886  NIHMSID: NIHMS1631948  PMID: 32941849

Abstract

N-glycosylation is a posttranslational modification that plays significant roles in regulating protein function. One form of N-glycosylation, polysialylation, has been implicated in many processes including learning and memory, addiction, and neurodegenerative disease. Polysialylation appears to be modulated by the estrous cycle in the hypothalamus in rat, but this has not been assessed in other brain regions. To determine if polysialylation was similarly estrous phase-dependent in other neuroanatomical structures, the percent area of polysialic acid (PSA) immunoreactivity in subregions of the medial prefrontal cortex, hippocampus, and nucleus accumbens was assessed in each of the four phases of adult female mice. In this study, we found that PSA immunoreactivity fluctuated across the estrous cycle in a subregion-specific manner. In the prefrontal cortex, PSA immunoreactivity was significantly lower in proestrus phase compared to estrus in the prelimbic cortex, but did not differ across the estrous cycle in the infralimbic cortex. In the hippocampus, PSA immunoreactivity was significantly increased in proestrus compared to metestrus in the CA1 and CA2 and compared to diestrus in CA3, but remain unchanged in the dentate gyrus. PSA immunoreactivity did not vary across the estrous cycle in the nucleus accumbens core or shell. These findings may have implications for estrous cycle-dependent alterations in behavior.

Keywords: N-glycosylation, polysialylation, estrous cycle, prefrontal cortex, nucleus accumbens, hippocampus

Introduction

N-glycosylation is a posttranslational modification involving the addition of a peptide with oligosaccharide side chains to the asparagine residue of a protein (Ohtsubo and Marth, 2006). These glycans can then modulate protein conformation, receptor signaling, activation, and trafficking, and the strength of protein-protein interactions (Ohtsubo and Marth, 2006). In the brain, N-glycosylation occurs on a variety of receptors, ion channels, and cell adhesion molecules (Scott and Panin, 2014).

The glycan polysialic acid (PSA) is an form of N-glycosylation with great specificity for its limited central nervous system targets, including the cell adhesion molecules neural cell adhesion molecule (NCAM) and synaptic cell adhesion molecule 1 (SynCAM1), and the receptor, neuropilin-2 (Mühlenhoff et al., 2013). NCAM modification has been the most thoroughly characterized. NCAM and SynCAM1 are surface glycoproteins that mediate homophilic and heterophilic cell-cell interactions and heterophilic cell-substrate interactions (Acheson et al., 1991; Fogel et al., 2007; Galuska et al., 2010), such as with extracellular matrix proteins. N-glycosylation appears to regulate cell adhesion, but in opposing directions for NCAM and SynCAM1. While N-glycosylation of NCAM leads to steric repulsion, promoting anti-adhesive properties (Johnson et al., 2005), adhesive strength of SynCAM1 can be either increased or decreased (Fogel et al., 2010).

NCAM and SynCAM1 are expressed by both excitatory and inhibitory neurons and by astrocytes. Their expression is regulated in a brain region-dependent manner from early postnatal development into adulthood (Di Cristo et al., 2007; Niquet et al., 1993; Ribic et al., 2019; Sandau et al., 2011; Seki and Arai, 1993; Thomas et al., 2008). Roles for PSA-NCAM and SynCAM1 include neurogenesis, synaptic plasticity, and modulation of spine density (Cremer et al., 2000; Doengi et al., 2016; Gascon et al., 2010, 2007; Guirado et al., 2014; Muller et al., 1996; Robbins et al., 2010). NCAM and SynCAM1 have both been implicated in learning and memory in males (Barker et al., 2012; Becker et al., 1996; Lopez-Fernandez et al., 2007; Robbins et al., 1999), with much of the work examining the role of N-glycosylated proteins focused on the role of PSA-NCAM in learning and memory in the hippocampus. Cleavage of PSA in the hippocampus via administration of the bacterial enzyme endo-neuraminidase (endo-N) impairs acquisition and expression of spatial memory and reduces contextual freezing following fear conditioning in male rats (Becker et al., 1996; Lopez-Fernandez et al., 2007). In addition, PSA-NCAM expression in the prefrontal cortex has been implicated in extinction of ethanol seeking in male mice (Barker et al., 2012). NCAM and SynCAM1 within the nucleus accumbens are sensitive to stress and drugs of abuse (Bessa et al., 2013; Giza et al., 2013; Kähler et al., 2020; Wang et al., 2020), suggesting a potential role for N-glycosylation in the nucleus accumbens as a mediator of synaptic structure and related behavior. To our knowledge, this has not yet been studied. PSA-NCAM expression also appears to be modulated by stress (Nacher et al., 2004a, 2004b; Pham et al., 2003) and in various neuropsychiatric diseases such as Schizophrenia, depression, and addiction (Barbeau et al., 1995; Gilabert-Juan et al., 2012; Varea et al., 2012; Weber et al., 2006).

Given the role of PSA in regulation of key neurocognitive functions, it is critical to extend research on PSA to females. To date, the majority of this research has been conducted exclusively in males and PSA-NCAM expression and function remains minimally characterized in females. The little data that do exist suggest that PSA-NCAM expression may change across the estrous cycle, at least in a subset of brain regions which may be a potential contributor to estrous-associated variations in synaptic plasticity and function. Specifically, PSA-NCAM immunoreactivity is increased in proestrus relative to metestrus in the hypothalamus (Tan et al., 2009), suggesting that polysialylation is regulated by circulating hormones. However, it is unclear if polysialylation varies across the estrous cycle in other brain regions.

Dendritic spine density is regulated by PSA in males (Guirado et al., 2014), though this is not characterized in females. Spine density varies across the estrous cycle and in response to estradiol administration, but the direction of these effects is brain region dependent with different patterns in the hippocampus, prefrontal cortex, and nucleus accumbens. In the CA1 subregion of hippocampus, spine density decreases from proestrus, when estradiol and progesterone levels are high in rats, to estrus, a low hormonal state (Woolley et al., 1990; Woolley and McEwen, 1993). Estradiol administration also increases dendritic spine density in the prefrontal cortex (Khan et al., 2013; Tuscher et al., 2016), but decreases spine density in the core, but not shell, of the nucleus accumbens (NAc) (Peterson et al., 2015). As spine density is regulated by both PSA and circulating hormones, we hypothesized that PSA expression would vary across the estrous cycle in a brain subregion-dependent manner. A thorough characterization of estrous cycle -associated changes in neuroplasticity-associated protein expression within key neurobiological substrates is critical for our comprehension of neurobehavioral and neurocognitive function in female mice. Thus, we evaluated PSA expression in each phase of the estrous cycle across subregions of the hippocampus, prefrontal cortex, and nucleus accumbens of adult female mice.

Materials and Methods

Subjects

Female C57BL/6J mice (n=27, 9 weeks, Jackson Laboratories) were group housed in same-sex cages in a temperature- and humidity-controlled environment and maintained under a 12h light/dark cycle with ad libitum access to food and water. All procedures were approved by the Institutional Animal Use and Care Committee at Drexel University.

Identification of estrous cycle

Mice were allowed to acclimate to the colony room for 1 week prior to handling. Following acclimation, mice were handled and monitored for at least two weeks prior to perfusion. Approximately 1–2 hours prior to perfusion at the same time every day (3 hours into the light cycle), vaginal cytology was used to monitor the phase of estrous cycle of C57BL/6J female mice. Vaginal cells were collected via lavage of the opening of the vaginal canal with saline (McLean et al., 2012). As the method employed for cell collection does not involve touching the vaginal opening or penetrating of the vaginal canal, the likelihood of inducing pseudopregnancy is minimized and we did not observe pseudopregnancy in any of the mice included in the study. The vaginal fluid collected was placed on a clean glass slide. Stage of the estrous cycle was determined by examining smears under a light microscope without staining. Mice were randomly assigned to be perfused in each of the four phases.

The proestrus phase was identified by the presence of primarily nucleated epithelial cells. The estrus phase was identified by the presence of predominantly cornified epithelial cells. The diestrus phase was identified by the presence of predominantly leucocytes. The metestrus phase was identified by a mixture of nucleated cells, cornified cells, and leucocytes.

Tissue Processing and Immunohistochemistry

Mice were transcardially perfused with 4% paraformaldehyde in each of the four phases of the estrous cycle. Brains were cryoprotected in 30% w/v sucrose and sliced using a cryostat to obtain 40μm coronal sections. Sections were incubated in 1% hydrogen peroxide solution for 1 hour to block endogenous peroxidase activity. Sections were blocked in 5% normal donkey serum for 1 hour followed by incubation with anti-PSA primary antibody (1:1000, Absolute Antibody, mab735, Oxford, UK) at room temperature overnight (18–24 hours), and biotinylated donkey anti-mouse secondary (1:1000, Jackson Labs, West Grove PA, 715–065-151) for 30 minutes. This antibody was selected as it has been well-validated for selectivity to PSA through the use of a variety of methods, including in a knockout mouse model and after enzymatic cleavage of PSA (Galuska et al., 2006; Husmann et al., 1990; Nakayama et al., 1998). Staining was visualized using nickel-enhanced DAB (Vector labs, Burlingame, CA, SK-4100) for 10 minutes. After staining, sections were mounted on plus slides and coverslipped with DPX mounting medium (Election Microscopy Science, Hatfield, PA). To control for any batch-to-batch differences in background staining, all batches contained representation from each phase of the estrous cycle.

To analyze PSA immunoreactivity, 10X images from 3 sections were taken and stitched together using Microsoft Image Composite Editor of slices in the prefrontal cortex (PFC, 1.54mm, 1.70mm, and 1.98mm anterior of Bregma), nucleus accumbens (NAc, 1.10mm, 1.42mm, and 1.70mm anterior of Bregma), and dorsal hippocampus subregions (−1.34mm, - 1.82mm, and −2.18mm posterior of Bregma). Due to the density of labeling, all images were analyzed bilaterally as percent area using ImageJ using an automated thresholding approach with manual adjustments for artifacts (Donnelly et al., 2009) under blinded conditions. We have established high interrator reliability with this technique and the blinded and predominantly automated nature of the analysis reduces experimenter bias. Animals were excluded from analysis if any of the three sections for a particular brain region were not available for analysis.

Statistical Analysis

Data were analyzed in GraphPad using one-way ANOVA when variances were equal for comparing percent area of staining in proestrus, estrus, metestrus, and diestrus, followed by Tukey’s multiple comparisons test when significant. When variances were not equal as indicated by Brown-Forsythe’s test, means were compared using Welch’s ANOVA, followed by Dunnett’s T3 multiple comparisons test when significant.

Results

Medial Prefrontal Cortex

To determine if estrous cycle impacted PSA expression in the prelimbic and infralimbic cortices, tissue from female mice sacrificed in each phase of the estrous cycle underwent immunohistochemical analysis and quantification of PSA immunoreactivity (Fig. 1a, 1b). In the prelimbic cortex, a Brown-Forsythe test revealed no significant differences in variance of percent area of PSA [F(3,19) = 1.658, p = 0.2097]. A one-way ANOVA of percent area of PSA immunoreactivity in the prelimbic cortex revealed a significant difference between groups [F(3,19) = 4.026, p = 0.022, η2=0.39] (Fig. 1c). Post hoc analyses indicated that PSA immunoreactivity was significantly decreased in proestrus compared to estrus (p = 0.035). In contrast, in the infralimbic cortex, a Brown-Forsythe test revealed a significant difference in the variances of percent area of PSA immunoreactivity [F(3,19) = 4.141, p = 0.048, η2=0.40] (Fig. 1d). Post hoc analyses revealed the variance in diestrus was significantly less than the variance in proestrus (p=0.0019) and metestrus (p=0.0078). Welch’s ANOVA revealed no significant differences in mean PSA immunoreactivity across groups [W(3,9) = 2.886, p = 0.0970].

Fig. 1. Estrous Cycle-Dependent PSA immunoreactivity in the Medial Prefrontal Cortex.

Fig. 1.

Open in a new tab

(a) Schematics of locations of prelimbic and infralimbic cortices. (b) Representative images of PSA immunoreactivity in the medial PFC in proestrus, estrus, metestrus, and diestrus. (c) Percent area of PSA immunoreactivity in the prelimbic cortex in each phase of the estrous cycle. (d) Percent area of PSA immunoreactivity in the infralimbic cortex in each phase of the estrous cycle. Dashed line represents median value, dotted lines represent quartiles, P* mean percent area p < 0.05 vs proestrus, P† variance p < 0.05 vs proestrus, M$ variance p < 0.05 vs metestrus

Hippocampus

To determine if estrous cycle impacted PSA expression in the CA1, CA2, CA3 and dentate gyrus subregions of the hippocampus, PSA immunoreactivity was quantified separately for each subregion in each of the four phases (Fig. 2a, 2b). In the CA1, A Brown-Forsythe test revealed a significant difference in the variances of percent area of PSA [F(3,23) = 3.303, p = 0.0382, η2=0.32] (Fig. 2c). Post hoc analyses revealed the variance in diestrus was significantly greater than the variance in proestrus (p=0.0011) and metestrus (p=0.0416) and the variance in estrus is significantly greater than the variance in proestrus (p=0.0184). Welch’s ANOVA revealed a significant difference in mean between groups in [W(3,11) = 6.923, p = 0.0068]. Post hoc analyses indicated that PSA immunoreactivity was significantly increased in proestrus compared to metestrus (p = 0.0407).

Fig. 2. Estrous Cycle-Dependent PSA immunoreactivity in the Hippocampus.

Fig. 2.

Open in a new tab

(a) Schematics of locations of CA1, CA2, CA3, and dentate gyrus. (b) Representative images of PSA immunoreactivity in the hippocampus in proestrus, estrus, metestrus, and diestrus. (c) Percent area of PSA immunoreactivity in the CA1 in each phase of the estrous cycle. (d) Percent area of PSA immunoreactivity in the CA2 in each phase of the estrous cycle. (e) Percent area of PSA immunoreactivity in the CA3 in each phase of the estrous cycle. (f) Percent area of PSA immunoreactivity in the dentate gyrus in each phase of the estrous cycle. Dashed line represents median value, dotted lines represent quartiles, P* mean percent area p < 0.05 vs proestrus, P† variance p < 0.05 vs proestrus, M$ variance p < 0.05 vs metestrus

In the CA2 subregion, a Brown-Forsythe test revealed a significant difference in the variances of percent area of PSA immunoreactivity [F(3,23) = 3.272, p = 0.0394, η2=0.22] (Fig. 2d). Post hoc analyses revealed the variance in diestrus was significantly greater than the variance in proestrus (p=0.0018) and metestrus (p=0.0381) and the variance in estrus is significantly greater than the variance in proestrus (p=0.0101). Welch’s ANOVA revealed a significant difference in mean between groups [W(3,11) = 5.747, p = 0.0126]. Post hoc analyses indicated that PSA immunoreactivity was significantly increased in proestrus compared to metestrus (p = 0.0321).

In the CA3, variance was not estrous phase-dependent [F(3,23) = 2.446, p = 0.0896, η2=0.30]. A one-way ANOVA revealed a significant difference among groups [F(3,23) = 3.236, p = 0.0408] (Fig. 2e). Post hoc analyses revealed that PSA immunoreactivity was significantly greater in proestrus compared to diestrus (p = 0.0268).

For the dentate gyrus, a Brown-Forsythe test revealed a significant difference in the variances of percent area of PSA immunoreactivity [F(3,23) = 4.262, p = 0.0156, η2=0.25] (Fig. 2f). Post hoc analyses revealed the variance in diestrus was significantly greater than the variance in proestrus (p=0.0136) and metestrus (p=0.0443). Welch’s ANOVA revealed no significant difference among groups [W(3,12) = 3.105, p = 0.0675].

Nucleus accumbens

To determine if estrous cycle impacted PSA expression in the core and shell of the nucleus accumbens, PSA immunoreactivity was analyzed in each of the four phases for both subregions (Fig. 3a, 3b). A Brown-Forsythe test revealed no significant differences in variance in either nucleus accumbens core [F(3,19) = 0.6314, p = 0.6038] or shell [F(3,19) = 0.3874, p = 0.7633]. A one way ANOVA of percent area of PSA immunoreactivity in the nucleus accumbens shell [F(3,19) = 0.936, p = 0.442, η2=0.13] (Fig. 3c) and core [F(3,19) = 0.979, p = 0.423, η2=0.13] (Fig. 3d) revealed no difference among groups.

Fig. 3. Estrous Cycle-Dependent PSA immunoreactivity in the Nucleus Accumbens.

Fig. 3.

Open in a new tab

(a) Schematics of locations of core and shell of nucleus accumbens. (b) Representative images of PSA immunoreactivity in the nucleus accumbens in proestrus, estrus, metestrus, and diestrus. (c) Percent area of PSA immunoreactivity in the nucleus accumbens shell in each phase of the estrous cycle. (d) Percent area of PSA immunoreactivity in the nucleus accumbens core in each phase of the estrous cycle. Dashed line represents median value, dotted lines represent quartiles

Discussion

Our findings demonstrate that PSA immunoreactivity varied across the estrous cycle in a brain subregion-specific manner, with opposing effects in discrete structures (Fig. 4). We found that PSA immunoreactivity was significantly higher in estrus compared to proestrus in the prelimbic cortex, but was significantly lower in metestrus compared to proestrus in CA1 and CA2 and in diestrus compared to proestrus in CA3. In contrast, we observed no estrous cycle-dependent changes in PSA immunoreactivity in the nucleus accumbens, dentate gyrus, and infralimbic cortex.

Fig. 4. Summary of estrous cycle-dependent PSA expression in the female mouse brain.

Fig. 4.

Open in a new tab

Solid lines represent approximate changes in mean across each phase for each brain subregion. Lighter shaded area represents changes in variance across the estrous cycle. Progesterone and estradiol curve schematics are based on McLean et al 2012. P* mean percent area p < 0.05 vs proestrus, P† variance p < 0.05 vs proestrus, M$ variance p < 0.05 vs metestrus

In the PFC, PSA immunoreactivity varied across the estrous phase in the prelimbic cortex, but not the infralimbic cortex. The prelimbic and infralimbic cortices play distinct roles in learning and memory (Ashwell and Ito, 2014; Sierra-Mercado et al., 2011) and project to distinct brain regions (Vertes, 2004). This increase in PSA expression in during estrus may have implications for behaviors dependent on the prelimbic cortex. For example, prelimbic cortex projections to the nucleus accumbens core appear to drive drug-primed reinstatement of cocaine seeking (McFarland et al., 2003), a behavior which is augmented in estrus females (Kippin et al., 2005).

In the hippocampus, PSA immunoreactivity varied across the estrous phase in CA1, CA2, and CA3. Given that estrous cycle-dependent alterations in spine density appear to be specific to CA1 (Woolley et al., 1990), we did not expect to observe similar alterations in CA2 and CA3. As depletion of PSA is associated with an increase in spine density and spine density in the CA1 is higher in proestrus compared to estrus (Woolley et al., 1990), contrary to our findings, we anticipated that PSA would be lower in proestrus in CA1. However, the study investigating PSA depletion was examining spine density on interneurons of the CA1, while estrous cycle effects on spine density have been characterized in pyramidal neurons. Thus, our findings may indicate that PSA regulation of spine density is distinct in differing neuronal subtypes. Alternatively, our findings identify modest changes in PSA expression across the estrous cycle, and it is possible that the impact of physiologically relevant fluctuations in PSA expression impact spine density differently from enzymatic depletion of PSA. Estrous cycle is also known to regulate spine morphology of pyramidal neurons, with mushroom type spines predominating in proestrus and thin type spines predominating in estrus (González-Burgos et al., 2005). Thus, it is possible that the decrease in PSA during estrus may be associated with the increased prevalence of immature, thin-type spines. These estrous cycle-related alterations in PSA immunoreactivity in the hippocampus may have implications for learning and memory. For example, as polysialylation of NCAM in the hippocampus appears to be an important contributor to fear conditioning in males (Lopez-Fernandez et al., 2007), it may be possible that estrous cycle-dependent alterations in fear conditioning (Markus and Zecevic, 1997; Milad et al., 2009) may be, in part, mediated by alterations in PSA expression. Notably, much of this work has been performed in rats in which hormone fluctuation patterns may be distinct from those observed in mice (Bastida et al., 2005; Bertolin and Murphy, 2014; Butts et al., 2010; Fata et al., 2001; McLean et al., 2012; Walmer et al., 1992), thus it will be important to determine how these findings generalize across species.

Further, targets of PSA are also expressed on other cell types, including astrocytes (Miñana et al., 1998; Sandau et al., 2011). Sialylation of astrocytic proteins is critical for activity-dependent changes in astrocyte morphology (Theodosis et al., 1999). Astrocytic volume in the CA1 is increased during estrus, which is hypothesized to compensate for the loss of dendritic spines observed in estrus (Klintsova et al., 1995) and mirrors the pattern of PSA immunoreactivity we observed in CA1. NCAM expression is also increased in reactive astrocytes in the hippocampus (Niquet et al., 1993) and astrocyte reactivity is regulated by the estrous cycle in the hippocampus (Arias et al., 2009; Struble et al., 2006). Thus, PSA expression of astrocytes may be contributing to the estrous cycle-related changes in total PSA immunoreactivity in the hippocampus. As hippocampal astrocytes actively participate in learning and memory (Adamsky et al., 2018; Bracchi-Ricard et al., 2008; Habbas et al., 2015; Suzuki et al., 2011), alterations in astrocyte PSA expression may also contribute to estrous cycle-dependent changes in behavior.

PSA expression did not vary across the estrous cycle in the dentate gyrus. PSA-NCAM expression in the dentate gyrus appears to be modulated by stressors such as chronic restraint stress or drug use in males (MaćKowiak et al., 2005; Pham et al., 2003; Weber et al., 2006). Thus, it is possible that estrous cycle-related alterations in PSA in the dentate gyrus may be uncovered under conditions in which stressors have been introduced, though this was not assessed in the current study.

In addition to significant differences in the mean immunoreactivity across the estrous cycle, we also observed significant differences in the variance in the infralimbic cortex and CA1, CA2, and dentate gyrus. These differences in range of expression may reflect differences in hormonal fluctuations, particularly in the case of the infralimbic cortex where there is a wide range of values in the proestrus phase. Alternatively, these differences in variance may indicate that only a subset of females are sensitive to changes in hormone level-induced alterations in PSA expression.

In contrast to the PFC and hippocampus, we did not observe estrous cycle-related differences in PSA immunoreactivity in either the shell or the core of the nucleus accumbens. To our knowledge, previous work has not investigated the relationship between polysialylation and synaptic plasticity in the nucleus accumbens. However, this brain region is known to be regulated by estradiol. Neuronal excitability in the nucleus accumbens is modulated by the estrous cycle (Proaño et al., 2018) and estradiol administration modulates spine density of medium spiny neurons in the nucleus accumbens core (Peterson et al., 2015). Thus, polysialylation may not be a major contributor to these estrous cycle-dependent alterations in excitability and spine density in the accumbens. Alternatively, as our findings did not differentiate between neuronal and glial expression of PSA, this lack of change in total PSA immunoreactivity does not preclude the possibility of cell type-specific alterations. Further, differential effects of estrous cycle on polysialylation of either NCAM or SynCAM1 may be masked by measuring total PSA.

In addition to its roles in healthy brain function, polysialylation has also been implicated in neurodegenerative disease and neuropsychiatric disorders including substance use disorders, and may have a role in other diseases with neurocognitive impairments such as HIV (Barbeau et al., 1995; Brennaman and Maness, 2010; El Maarouf et al., 2006; Gilabert-Juan et al., 2012; Poluektova et al., 2005; Sato et al., 2016; Schnaar et al., 2014; Varea et al., 2012; Weber et al., 2006). As the prevalence, symptoms, and long term outcomes of neuropsychiatric and neurodegenerative disorders are frequently sex-dependent (Altemus et al., 2014; Giacometti and Barker, 2020; Ullah et al., 2019), we believe these data will have implications for our understanding of the neurobiological basis of sex differences in risk and prognosis of neuropsychiatric and neurodegenerative disease.

Together, these data suggest that N-glycosylation may be regulated by the estrous cycle in a brain region-specific manner. These alterations are likely driven by circulating estradiol, as all alterations occurred in proestrus, a phase characterized by high levels of estradiol, relative to low estradiol phases. However, it is possible that increases in progesterone during the diestrus phase may contribute to alterations during this phase and subsequent studies should interrogate the independent and interactive roles of progesterone and estradiol. Interestingly, the direction of changes in proestrus relative to other phases was not unidirectional, suggesting that the relationship between estradiol and PSA expression may be cell type- or brain region-specific. This estrous cycle-dependent regulation will likely have implications for estrous cycle-dependent behavioral changes. Further, naturally occurring cyclicity in PSA expression may relate to periods of heightened vulnerability to stress-, infection-, or drug-induced alterations in neural plasticity and function across the estrous cycle, which will inform understanding of the neurobiological consequences of these insults.

Highlights.

  • Estrous cycle modulates total polysialic acid immunoreactivity as well as variance

  • PSA immunoreactivity was modulated in the prelimbic PFC and hippocampal subregions

  • Estrous cycle did not modulate polysialic acid immunoreactivity in nucleus accumbens

Acknowledgements

This research was supported by NIH grant DA047919 (JMB). FH was supported by funds from the China Scholarship Council. BSH was supported by the NIH Interdisciplinary and Translational Research Training in NeuroAIDS grant MH079785.

Footnotes

Declaration of competing interest

The authors declare that they have no competing interests.

Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

References

  1. Acheson A, Sunshine JL, Rutishauser U, 1991. NCAM polysialic acid can regulate both cell-cell and cell-substrate interactions. J. Cell Biol 114, 143–153. 10.1083/jcb.114.1.143 [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Adamsky A, Kol A, Kreisel T, Doron A, Ozeri-Engelhard N, Melcer T, Refaeli R, Horn H, Regev L, Groysman M, London M, Goshen I, 2018. Astrocytic Activation Generates De Novo Neuronal Potentiation and Memory Enhancement. Cell 174, 59–71.e14. 10.1016/j.cell.2018.05.002 [DOI] [PubMed] [Google Scholar]
  3. Altemus M, Sarvaiya N, Neill Epperson C, 2014. Sex differences in anxiety and depression clinical perspectives. Front. Neuroendocrinol 35, 320–330. 10.1016/j.yfrne.2014.05.004 [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Arias C, Zepeda A, Hernández-Ortega K, Leal-Galicia P, Lojero C, Camacho-Arroyo I, 2009. Sex and estrous cycle-dependent differences in glial fibrillary acidic protein immunoreactivity in the adult rat hippocampus. Horm. Behav 55, 257–263. 10.1016/j.yhbeh.2008.10.016 [DOI] [PubMed] [Google Scholar]
  5. Ashwell R, Ito R, 2014. Excitotoxic lesions of the infralimbic, but not prelimbic cortex facilitate reversal of appetitive discriminative context conditioning: The role of the infralimbic cortex in context generalization. Front. Behav. Neurosci 8 10.3389/fnbeh.2014.00063 [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Barbeau D, Liang JJ, Robitaille Y, Quirion R, Srivastava LK, 1995. Decreased expression of the embryonic form of the neural cell adhesion molecule in schizophrenic brains. Proc. Natl. Acad. Sci. U. S. A 92, 2785–2789. 10.1073/pnas.92.7.2785 [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Barker JM, Torregrossa MM, Taylor JR, 2012. Low prefrontal PSA-NCAM confers risk for alcoholism-related behavior. Nat. Neurosci 15, 1356–1358. 10.1038/nn.3194 [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Bastida CM, Cremades A, Castells MT, López-Contreras AJ, López-García C, Tejada F, Peñafiel R, 2005. Influence of ovarian ornithine decarboxylase in folliculogenesis and luteinization. Endocrinology 146, 666–674. 10.1210/en.2004-1004 [DOI] [PubMed] [Google Scholar]
  9. Becker CG, Artola A, Gerardy-Schahn R, Becker T, Welzl H, Schachner M, 1996. The polysialic acid modification of the neural cell adhesion molecule is involved in spatial learning and hippocampal long-term potentiation. J. Neurosci. Res 45, 143–152. [DOI] [PubMed] [Google Scholar]
  10. Bertolin K, Murphy BD, 2014. Reproductive Tract Changes During the Mouse Estrous Cycle, in: The Guide to Investigation of Mouse Pregnancy. pp. 85–94. 10.1016/b978-0-12-394445-0.00007-2 [DOI] [Google Scholar]
  11. Bessa JM, Morais M, Marques F, Pinto L, Palha JA, Almeida OFX, Sousa N, 2013. Stress-induced anhedonia is associated with hypertrophy of medium spiny neurons of the nucleus accumbens. Transl. Psychiatry 3, e266 10.1038/tp.2013.39 [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Bracchi-Ricard V, Brambilla R, Levenson J, Hu WH, Bramwell A, Sweatt JD, Green EJ, Bethea JR, 2008. Astroglial nuclear factor-κB regulates learning and memory and synaptic plasticity in female mice. J. Neurochem 104, 611–623. 10.1111/j.1471-4159.2007.04993.x [DOI] [PubMed] [Google Scholar]
  13. Brennaman LH, Maness PF, 2010. NCAM in neuropsychiatric and neurodegenerative disorders. Adv. Exp. Med. Biol 663, 299–317. 10.1007/978-1-4419-1170-4_19 [DOI] [PubMed] [Google Scholar]
  14. Butts CL, Candando KM, Warfel J, Belyavskaya E, D’Agnillo F, Sternberg EM, 2010. Progesterone regulation of uterine dendritic cell function in rodents is dependent on the stage of estrous cycle. Mucosal Immunol. 3, 496–505. 10.1038/mi.2010.28 [DOI] [PubMed] [Google Scholar]
  15. Cremer H, Chazal G, Lledo PM, Rougon G, Montaron MF, Mayo W, Le Moal M, Abrous DN, 2000. PSA-NCAM: An important regulator of hippocampal plasticity, in: International Journal of Developmental Neuroscience. pp. 213–220. 10.1016/S0736-5748(99)00090-8 [DOI] [PubMed] [Google Scholar]
  16. Di Cristo G, Chattopadhyaya B, Kuhlman SJ, Fu Y, Bélanger MC, Wu CZ, Rutishauser U, Maffei L, Huang ZJ, 2007. Activity-dependent PSA expression regulates inhibitory maturation and onset of critical period plasticity. Nat. Neurosci 10, 1569–1577. 10.1038/nn2008 [DOI] [PubMed] [Google Scholar]
  17. Doengi M, Krupp AJ, Körber N, Stein V, 2016. SynCAM 1 improves survival of adult-born neurons by accelerating synapse maturation. Hippocampus 26, 319–328. 10.1002/hipo.22524 [DOI] [PubMed] [Google Scholar]
  18. Donnelly DJ, Gensel JC, Ankeny DP, van Rooijen N, Popovich PG, 2009. An efficient and reproducible method for quantifying macrophages in different experimental models of central nervous system pathology. J. Neurosci. Methods 181, 36–44. 10.1016/j.jneumeth.2009.04.010 [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. El Maarouf A, Petridis AK, Rutishauser U, 2006. Use of polysialic acid in repair of the central nervous system. Proc. Natl. Acad. Sci. U. S. A 103, 16989–16994. 10.1073/pnas.0608036103 [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Fata JE, Chaudhary V, Khokha R, 2001. Cellular turnover in the mammary gland is correlated with systemic levels of progesterone and not 17β-estradiol during the estrous cycle. Biol. Reprod 65, 680–688. 10.1095/biolreprod65.3.680 [DOI] [PubMed] [Google Scholar]
  21. Fogel AI, Akins MR, Krupp AJ, Stagi M, Stein V, Biederer T, 2007. SynCAMs organize synapses through heterophilic adhesion. J. Neurosci 27, 12516–12530. 10.1523/JNEUROSCI.2739-07.2007 [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Fogel AI, Li Y, Giza J, Wang Q, Lam TKT, Modis Y, Biederer T, 2010. N-glycosylation at the SynCAM (Synaptic Cell Adhesion Molecule) immunoglobulin interface modulates synaptic adhesion. J. Biol. Chem 285, 34864–34874. 10.1074/jbc.M110.120865 [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Galuska SP, Oltmann-Norden I, Geyer H, Weinhold B, Kuchelmeister K, Hildebrandt H, Gerardy-Schahn R, Geyer R, Mühlenhoff M, 2006. Polysialic acid profiles of mice expressing variant allelic combinations of the polysialyltransferases ST8SiaII and ST8SiaIV. J. Biol. Chem 281, 31605–31615. 10.1074/jbc.M606516200 [DOI] [PubMed] [Google Scholar]
  24. Galuska SP, Rollenhagen M, Kaup M, Eggers K, Oltmann-Norden I, Schiff M, Hartmann M, Weinhold B, Hildebrandt H, Geyer R, Mühlenhoff M, Geyer H, 2010. Synaptic cell adhesion molecule SynCAM 1 is a target for polysialylation in postnatal mouse brain. Proc. Natl. Acad. Sci. U. S. A 107, 10250–10255. 10.1073/pnas.0912103107 [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Gascon E, Vutskits L, Kiss JZ, 2010. The role of PSA-NCAM in adult neurogenesis. Adv. Exp. Med. Biol 663, 127–136. 10.1007/978-1-4419-1170-4_8 [DOI] [PubMed] [Google Scholar]
  26. Gascon E, Vutskits L, Kiss JZ, 2007. Polysialic acid-neural cell adhesion molecule in brain plasticity: From synapses to integration of new neurons. Brain Res. Rev 56, 101–118. 10.1016/j.brainresrev.2007.05.014 [DOI] [PubMed] [Google Scholar]
  27. Giacometti LL, Barker JM, 2020. Sex differences in the glutamate system: Implications for addiction. Neurosci. Biobehav. Rev 113, 157–168. 10.1016/j.neubiorev.2020.03.010 [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Gilabert-Juan J, Varea E, Guirado R, Blasco-Ibáñez JM, Crespo C, Nácher J, 2012. Alterations in the expression of PSA-NCAM and synaptic proteins in the dorsolateral prefrontal cortex of psychiatric disorder patients. Neurosci. Lett 530, 97–102. 10.1016/j.neulet.2012.09.032 [DOI] [PubMed] [Google Scholar]
  29. Giza JI, Jung Y, Jeffrey RA, Neugebauer NM, Picciotto MR, Biederer T, 2013. The synaptic adhesion molecule SynCAM 1 contributes to cocaine effects on synapse structure and psychostimulant behavior. Neuropsychopharmacology 38, 628–638. 10.1038/npp.2012.226 [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. González-Burgos I, Alejandre-Gómez M, Cervantes M, 2005. Spine-type densities of hippocampal CA1 neurons vary in proestrus and estrus rats. Neurosci. Lett 379, 52–54. 10.1016/j.neulet.2004.12.043 [DOI] [PubMed] [Google Scholar]
  31. Guirado R, Perez-Rando M, Sanchez-Matarredona D, Castillo-Gómez E, Liberia T, Rovira-Esteban L, Varea E, Crespo C, Blasco-Ibáñez JM, Nacher J, 2014. The dendritic spines of interneurons are dynamic structures influenced by PSA-NCAM expression. Cereb. Cortex 24, 3014–3024. 10.1093/cercor/bht156 [DOI] [PubMed] [Google Scholar]
  32. Habbas S, Santello M, Becker D, Stubbe H, Zappia G, Liaudet N, Klaus FR, Kollias G, Fontana A, Pryce CR, Suter T, Volterra A, 2015. Neuroinflammatory TNFα Impairs Memory via Astrocyte Signaling. Cell 163, 1730–1741. 10.1016/j.cell.2015.11.023 [DOI] [PubMed] [Google Scholar]
  33. Husmann M, Roth J, Kabat EA, Weisgerber C, Frosch M, Bitter-Suermann D, 1990. Immunohistochemical localization of polysialic acid in tissue sections: Differential binding to polynucleotides and DNA of a murine IgG and a human IgM monoclonal antibody. J. Histochem. Cytochem 38, 209–215. 10.1177/38.2.1688896 [DOI] [PubMed] [Google Scholar]
  34. Johnson CP, Fujimoto I, Rutishauser U, Leckband DE, 2005. Direct evidence that Neural Cell Adhesion Molecule (NCAM) polysialylation increases intermembrane repulsion and abrogates adhesion. J. Biol. Chem 280, 137–145. 10.1074/jbc.M410216200 [DOI] [PubMed] [Google Scholar]
  35. Kähler B, Romswinkel EV, Jakovcevski M, Moses A, Schachner M, Morellini F, 2020. Hyperfunction of the stress response system and novelty-induced hyperactivity correlate with enhanced cocaine-induced conditioned place preference in NCAM-deficient mice. Addict. Biol 10.1111/adb.12887 [DOI] [PubMed] [Google Scholar]
  36. Khan MM, Dhandapani KM, Zhang QG, Brann DW, 2013. Estrogen regulation of spine density and excitatory synapses in rat prefrontal and somatosensory cerebral cortex, in: Steroids. pp. 614–623. 10.1016/j.steroids.2012.12.005 [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Kippin TE, Fuchs RA, Mehta RH, Case JM, Parker MP, Bimonte-Nelson HA, See RE, 2005. Potentiation of cocaine-primed reinstatement of drug seeking in female rats during estrus. Psychopharmacology (Berl). 182, 245–252. 10.1007/s00213-005-0071-y [DOI] [PubMed] [Google Scholar]
  38. Klintsova A, Levy WB, Desmond NL, 1995. Astrocytic volume fluctuates in the hippocampal CA1 region across the estrous cycle. Brain Res. 690, 269–274. 10.1016/0006-8993(95)00642-4 [DOI] [PubMed] [Google Scholar]
  39. Lopez-Fernandez MA, Montaron MF, Varea E, Rougon G, Venero C, Abrous DN, Sandi C, 2007. Upregulation of polysialylated neural cell adhesion molecule in the dorsal hippocampus after contextual fear conditioning is involved in long-term memory formation. J. Neurosci 27, 4552–4561. 10.1523/JNEUROSCI.0396-07.2007 [DOI] [PMC free article] [PubMed] [Google Scholar]
  40. MaćKowiak M, Markowicz-Kula K, Fijał K, Wȩdzony K, 2005. Acute and repeated administration of cocaine differentially regulates expression of PSA-NCAM-positive neurons in the rat hippocampus. Brain Res. 1055, 149–155. 10.1016/j.brainres.2005.07.001 [DOI] [PubMed] [Google Scholar]
  41. Markus EJ, Zecevic M, 1997. Sex differences and estrous cycle changes in hippocampus-dependent fear conditioning. Psychobiology 25, 246–252. 10.3758/BF03331934 [DOI] [Google Scholar]
  42. McFarland K, Lapish CC, Kalivas PW, 2003. Prefrontal glutamate release into the core of the nucleus accumbens mediates cocaine-induced reinstatement of drug-seeking behavior. J. Neurosci 23, 3531–3537. 10.1523/jneurosci.23-08-03531.2003 [DOI] [PMC free article] [PubMed] [Google Scholar]
  43. McLean AC, Valenzuela N, Fai S, Bennett SAL, 2012. Performing vaginal lavage, crystal violet staining, and vaginal cytological evaluation for mouse estrous cycle staging identification. J. Vis. Exp 67, e4389 10.3791/4389 [DOI] [PMC free article] [PubMed] [Google Scholar]
  44. Milad MR, Igoe SA, Lebron-Milad K, Novales JE, 2009. Estrous cycle phase and gonadal hormones influence conditioned fear extinction. Neuroscience 164, 887–895. 10.1016/j.neuroscience.2009.09.011 [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Miñana R, Sancho-Tello M, Climent E, Seguí JM, Renau-Piqueras J, Guerri C, 1998. Intracellular location, temporal expression, and polysialylation of neural cell adhesion molecule in astrocytes in primary culture. Glia 24, 415–427. [DOI] [PubMed] [Google Scholar]
  46. Mühlenhoff M, Rollenhagen M, Werneburg S, Gerardy-Schahn R, Hildebrandt H, 2013. Polysialic acid: Versatile modification of NCAM, SynCAM 1 and neuropilin-2. Neurochem. Res 38, 1134–1143. 10.1007/s11064-013-0979-2 [DOI] [PubMed] [Google Scholar]
  47. Muller D, Wang C, Skibo G, Toni N, Cremer H, Calaora V, Rougon G, Kiss JZ, 1996. PSA-NCAM is required for activity-induced synaptic plasticity. Neuron 17, 413–422. 10.1016/S0896-6273(00)80174-9 [DOI] [PubMed] [Google Scholar]
  48. Nacher J, Gomez-Climent MA, McEwen B, 2004a. Chronic non-invasive glucocorticoid administration decreases polysialylated neural cell adhesion molecule expression in the adult rat dentate gyrus. Neurosci. Lett 370, 40–44. 10.1016/j.neulet.2004.07.062 [DOI] [PubMed] [Google Scholar]
  49. Nacher J, Pham K, Gil-Fernandez V, McEwen B, 2004b. Chronic restraint stress and chronic corticosterone treatment modulate differentially the expression of molecules related to structural plasticity in the adult rat piriform cortex. Neuroscience 126, 503–509. 10.1016/j.neuroscience.2004.03.038 [DOI] [PubMed] [Google Scholar]
  50. Nakayama J, Angata K, Ong E, Katsuyama T, Fukuda M, 1998. Polysialic acid, a unique glycan that is developmentally regulated by two polysialyltransferases, PST and STX, in the central nervous system: From biosynthesis to function. Pathol. Int 48, 665–677. 10.1111/j.1440-1827.1998.tb03967.x [DOI] [PubMed] [Google Scholar]
  51. Niquet J, Jorquera I, Ben-Ari Y, Represa A, 1993. NCAM immunoreactivity on mossy fibers and reactive astrocytes in the hippocampus of epileptic rats. Brain Res. 626, 106–116. 10.1016/0006-8993(93)90569-9 [DOI] [PubMed] [Google Scholar]
  52. Ohtsubo K, Marth JD, 2006. Glycosylation in Cellular Mechanisms of Health and Disease. Cell. 126, 855–867. 10.1016/j.cell.2006.08.019 [DOI] [PubMed] [Google Scholar]
  53. Peterson BM, Mermelstein PG, Meisel RL, 2015. Estradiol mediates dendritic spine plasticity in the nucleus accumbens core through activation of mGluR5. Brain Struct. Funct 220, 2415–2422. 10.1007/s00429-014-0794-9 [DOI] [PMC free article] [PubMed] [Google Scholar]
  54. Pham K, Nacher J, Hof PR, McEwen BS, 2003. Repeated restraint stress suppresses neurogenesis and induces biphasic PSA-NCAM expression in the adult rat dentate gyrus. Eur. J. Neurosci 17, 879–886. 10.1046/j.1460-9568.2003.02513.x [DOI] [PubMed] [Google Scholar]
  55. Poluektova L, Meyer V, Walters L, Paez X, Gendelman HE, 2005. Macrophage-induced inflammation affects hippocampal plasticity and neuronal development in a murine model of HIV-1 encephalitis. Glia 52, 344–353. 10.1002/glia.20253 [DOI] [PubMed] [Google Scholar]
  56. Proaño SB, Morris HJ, Kunz LM, Dorris DM, Meitzen J, 2018. Estrous cycle-induced sex differences in medium spiny neuron excitatory synaptic transmission and intrinsic excitability in adult rat nucleus accumbens core. J. Neurophysiol 120, 1356–1373. 10.1152/jn.00263.2018 [DOI] [PMC free article] [PubMed] [Google Scholar]
  57. Ribic A, Biederer T, Morishita H, 2019. Emerging Roles of Synapse Organizers in the Regulation of Critical Periods. Neural Plast. 2019. 10.1155/2019/1538137 [DOI] [PMC free article] [PubMed] [Google Scholar]
  58. Robbins EM, Krupp AJ, Perez de Arce K, Ghosh AK, Fogel AI, Boucard A, Südhof TC, Stein V, Biederer T, 2010. SynCAM 1 Adhesion Dynamically Regulates Synapse Number and Impacts Plasticity and Learning. Neuron 68, 894–906. 10.1016/j.neuron.2010.11.003 [DOI] [PMC free article] [PubMed] [Google Scholar]
  59. Robbins SJ, Ehrman RN, Childress AR, O’Brien CP, 1999. Comparing levels of cocaine cue reactivity in male and female outpatients. Drug Alcohol Depend. 53, 223–230. 10.1016/S0376-8716(98)00135-5 [DOI] [PubMed] [Google Scholar]
  60. Sandau US, Mungenast AE, Alderman Z, Sardi SP, Fogel AI, Taylor B, Parent AS, Biederer T, Corfas G, Ojeda SR, 2011. SynCAM1, a synaptic adhesion molecule, is expressed in astrocytes and contributes to erbB4 receptor-mediated control of female sexual development. Endocrinology 152, 2364–2376. 10.1210/en.2010-1435 [DOI] [PMC free article] [PubMed] [Google Scholar]
  61. Sato C, Hane M, Kitajima K, 2016. Relationship between ST8SIA2, polysialic acid and its binding molecules, and psychiatric disorders. Biochim. Biophys. Acta - Gen. Subj 1860, 1739–1752. 10.1016/j.bbagen.2016.04.015 [DOI] [PubMed] [Google Scholar]
  62. Schnaar RL, Gerardy-Schahn R, Hildebrandt H, 2014. Sialic acids in the brain: Gangliosides and polysialic acid in nervous system development, stability, disease, and regeneration. Physiol. Rev 94, 461–518. 10.1152/physrev.00033.2013 [DOI] [PMC free article] [PubMed] [Google Scholar]
  63. Scott H, Panin VM, 2014. N-Glycosylation in Regulation of the Nervous System. pp. 367–394. 10.1007/978-1-4939-1154-7_17 [DOI] [PMC free article] [PubMed] [Google Scholar]
  64. Seki T, Arai Y, 1993. Distribution and possible roles of the highly polysialylated neural cell adhesion molecule (NCAM-H) in the developing and adult central nervous system. Neurosci. Res 17, 265–290. 10.1016/0168-0102(93)90111-3 [DOI] [PubMed] [Google Scholar]
  65. Sierra-Mercado D, Padilla-Coreano N, Quirk GJ, 2011. Dissociable roles of prelimbic and infralimbic cortices, ventral hippocampus, and basolateral amygdala in the expression and extinction of conditioned fear. Neuropsychopharmacology 36, 529–538. 10.1038/npp.2010.184 [DOI] [PMC free article] [PubMed] [Google Scholar]
  66. Struble RG, Afridi S, Beckman-Randall S, Li M, Cady C, Nathan B, McAsey ME, 2006. Neocortical and hippocampal glial fibrillary acidic protein immunoreactivity shows region-specific variation during the mouse estrous cycle. Neuroendocrinology 83, 325–335. 10.1159/000095340 [DOI] [PubMed] [Google Scholar]
  67. Suzuki A, Stern SA, Bozdagi O, Huntley GW, Walker RH, Magistretti PJ, Alberini CM, 2011. Astrocyte-neuron lactate transport is required for long-term memory formation. Cell 144, 810–823. 10.1016/j.cell.2011.02.018 [DOI] [PMC free article] [PubMed] [Google Scholar]
  68. Tan O, Fadiel A, Chang A, Demir N, Jeffrey R, Horvath T, Garcia-Segura LM, Naftolin F, 2009. Estrogens regulate posttranslational modification of neural cell adhesion molecule during the estrogen-induced gonadotropin surge. Endocrinology 150, 2783–2790. 10.1210/en.2008-0927 [DOI] [PubMed] [Google Scholar]
  69. Theodosis DT, Bonhomme R, Vitiello S, Rougon G, Poulain DA, 1999. Cell surface expression of polysialic acid on NCAM is a prerequisite for activity-dependent morphological neuronal and glial plasticity. J. Neurosci 19, 10228–10236. 10.1523/jneurosci.19-23-10228.1999 [DOI] [PMC free article] [PubMed] [Google Scholar]
  70. Thomas LA, Akins MR, Biederer T, 2008. Expression and adhesion profiles of SynCAM molecules indicate distinct neuronal functions. J. Comp. Neurol 510, 47–67. 10.1002/cne.21773 [DOI] [PMC free article] [PubMed] [Google Scholar]
  71. Tuscher JJ, Luine V, Frankfurt M, Frick KM, 2016. Estradiol-mediated spine changes in the dorsal hippocampus and medial prefrontal cortex of ovariectomized female mice depend on ERK and mTOR activation in the dorsal hippocampus. J. Neurosci 36, 1483–1489. 10.1523/JNEUROSCI.3135-15.2016 [DOI] [PMC free article] [PubMed] [Google Scholar]
  72. Ullah MF, Ahmad A, Bhat SH, Abu-Duhier FM, Barreto GE, Ashraf GM, 2019. Impact of sex differences and gender specificity on behavioral characteristics and pathophysiology of neurodegenerative disorders. Neurosci. Biobehav. Rev 102, 95–105. 10.1016/j.neubiorev.2019.04.003 [DOI] [PubMed] [Google Scholar]
  73. Varea E, Guirado R, Gilabert-Juan J, Martí U, Castillo-Gomez E, Blasco-Ibáñez JM, Crespo C, Nacher J, 2012. Expression of PSA-NCAM and synaptic proteins in the amygdala of psychiatric disorder patients. J. Psychiatr. Res 46, 189–197. 10.1016/j.jpsychires.2011.10.011 [DOI] [PubMed] [Google Scholar]
  74. Vertes RP, 2004. Differential Projections of the Infralimbic and Prelimbic Cortex in the Rat. Synapse 51, 32–58. 10.1002/syn.10279 [DOI] [PubMed] [Google Scholar]
  75. Walmer DK, Wrona MA, Hughes CL, Nelson KG, 1992. Lactoferrin expression in the mouse reproductive traci during the natural estrous cycle: Correlation with circulating estradiol and progesterone. Endocrinology 131, 1458–1466. 10.1210/endo.131.3.1505477 [DOI] [PubMed] [Google Scholar]
  76. Wang C, Inselman A, Liu S, Liu F, 2020. Potential mechanisms for phencyclidine/ketamine-induced brain structural alterations and behavioral consequences. Neurotoxicology. 76, 213–219. 10.1016/j.neuro.2019.12.005 [DOI] [PubMed] [Google Scholar]
  77. Weber M, Modemann S, Schipper P, Trauer H, Franke H, Illes P, Geiger KD, Hengstler JG, Kleemann WJ, 2006. Increased polysialic acid neural cell adhesion molecule expression in human hippocampus of heroin addicts. Neuroscience 138, 1215–1223. 10.1016/j.neuroscience.2005.11.059 [DOI] [PubMed] [Google Scholar]
  78. Woolley CS, Gould E, Frankfurt M, McEwen BS, 1990. Naturally occurring fluctuation in dendritic spine density on adult hippocampal pyramidal neurons. J. Neurosci 10, 4035–4039. 10.1523/jneurosci.10-12-04035.1990 [DOI] [PMC free article] [PubMed] [Google Scholar]
  79. Woolley CS, McEwen BS, 1993. Roles of estradiol and progesterone in regulation of hippocampal dendritic spine density during the estrous cycle in the rat. J. Comp. Neurol 336, 293–306. 10.1002/cne.903360210 [DOI] [PubMed] [Google Scholar]

RESOURCES