Antidepressant effects of estrogens: a basic approximation

The intersection between menopause and depression: overview of research using animal models

Menopausal women may experience symptoms of depression, sometimes even progressing clinical depression requiring treatment to improve quality of life. While varying levels of estrogen in perimenopause may contribute to an increased biological vulnerability to mood disturbances, the effectiveness of estrogen replacement therapy (ERT) in the relief of depressive symptoms remains controversial. Menopausal depression has a complex, multifactorial etiology, that has limited the identification of optimal treatment strategies for the management of this psychiatric complaint. Nevertheless, clinical evidence increasingly supports the notion that estrogen exerts neuroprotective effects on brain structures related to mood regulation. Indeed, research using preclinical animal models continues to improve our understanding of menopause and the effectiveness of ERT and other substances at treating depression-like behaviors. However, questions regarding the efficacy of ERT in perimenopause have been raised. These questions may be answered by further investigation using specific animal models of reduced ovarian function. This review compares and discusses the advantages and pitfalls of different models emulating the menopausal stages and their relationship with the onset of depressive-like signs, as well as the efficacy and mechanisms of conventional and novel ERTs in treating depressive-like behavior. Ovariectomized young rats, middle-to-old aged intact rats, and females treated with reprotoxics have all been used as models of menopause, with stages ranging from surgical menopause to perimenopause. Additionally, this manuscript discusses the impact of organistic and therapeutic variables that may improve or reduce the antidepressant response of females to ERT. Findings from these models have revealed the complexity of the dynamic changes occurring in brain function during menopausal transition, reinforcing the idea that the best approach is timely intervention considering the opportunity window, in addition to the careful selection of treatment according to the presence or absence of reproductive tissue. Additionally, data from animal models has yielded evidence to support new promising estrogens that could be considered as ERTs with antidepressant properties and actions in endocrine situations in which traditional ERTs are not effective.

Exploring the Feasibility of Estrogen Replacement Therapy as a Treatment for Perimenopausal Depression: A Comprehensive Literature Review

Perimenopausal depression (PMD) is a psychological disorder that occurs in women during perimenopause. In addition to the common clinical symptoms of depression, it often manifests as a perimenopausal complication, and its notable cause is the decline in estrogen levels. Despite numerous studies and trials confirming the benefits of estrogen replacement therapy (ERT) for PMD, ERT remains unapproved for treating PMD. Therefore, we conducted a literature search using selected keywords in PubMed and Google Scholar to write a review discussing the feasibility of using ERT for PMD. This review examines the potential of ERT for PMD in terms of its underlying mechanisms, efficacy, safety, and time window. These four aspects suggest that ERT is a viable option for PMD treatment. However, the risk of thrombosis and stroke with ERT is a matter of contention among medical experts, with a paucity of clinical data. Consequently, further clinical trial data are required to ascertain the safety of ERT.

Sex differences in the relationship between depression and Alzheimer's disease-mechanisms, genetics, and therapeutic opportunities

Depression and Alzheimer's disease (AD) are prevalent neuropsychiatric disorders with intriguing epidemiological overlaps. Their interrelation has recently garnered widespread attention. Empirical evidence indicates that depressive disorders significantly contribute to AD risk, and approximately a quarter of AD patients have comorbid major depressive disorder, which underscores the bidirectional link between AD and depression. A growing body of evidence substantiates pervasive sex differences in both AD and depression: both conditions exhibit a higher incidence among women than among men. However, the available literature on this topic is somewhat fragmented, with no comprehensive review that delineates sex disparities in the depression-AD correlation. In this review, we bridge these gaps by summarizing recent progress in understanding sex-based differences in mechanisms, genetics, and therapeutic prospects for depression and AD. Additionally, we outline key challenges in the field, holding potential for improving treatment precision and efficacy tailored to male and female patients' distinct needs.

Role of estrogen in treatment of female depression

Depression is a neurological disorder that profoundly affects human physical and mental health, resulting in various changes in the central nervous system. Despite several prominent hypotheses, such as the monoaminergic theory, hypothalamic-pituitary-adrenal (HPA) axis theory, neuroinflammation, and neuroplasticity, the current understanding of depression's pathogenesis remains incomplete. Importantly, depression is a gender-dimorphic disorder, with women exhibiting higher incidence rates than men. Given estrogen's pivotal role in the menstrual cycle, it is reasonable to postulate that its fluctuating levels could contribute to the pathogenesis of depression. Estrogen acts by binding to a diversity of receptors, which are widely distributed in the central nervous system. An abundance of research has established that estrogen and its receptors play a crucial role in depression, spanning pathogenesis and treatment. In this comprehensive review, we provide an in-depth analysis of the fundamental role of estrogen and its receptors in depression, with a focus on neuroinflammation, neuroendocrinology, and neuroplasticity. Furthermore, we discuss potential mechanisms underlying the therapeutic effects of estrogen in the treatment of depression, which may pave the way for new antidepressant drug development and alternative treatment options.

Dietary flavonoid intake is associated with a lower risk of depressive symptoms in US adults: Data from NHANES 2007-2008, 2009-2010, and 2017-2018

BACKGROUND

Depressive symptoms is an important public health problem. The aim of the present study is to examine the association of dietary flavonoid intake with risk of depressive symptoms.

METHODS

In this study, we conducted an assessment to investigate the potential association between dietary flavonoid intake and the risk of depressive symptoms. Our analysis was based on a nationally representative sample of 9674 adults who participated in the 2007-2010 and 2017-2018 National Health and Nutrition Examination Surveys. Flavonoid intake was measured using a 24-hour dietary recall method, while depressive symptoms was evaluated using the Patient Health Questionnaire-9. To examine the relationship between dietary flavonoid intake and the risk of depressive symptoms, we employed logistic regression, subgroup and restricted cubic spline models.

RESULTS

Following multivariate adjustment, the study found a negative association between total flavonoids, anthocyanidins, flavanones, flavones, isoflavones and the risk of depressive symptoms. In subgroup analysis, total flavonoid intake was inversely associated with risk of depressive symptoms among women whereas no association was found among man. Additionally, a non-linear relationship was observed between total flavonoid intake and depressive symptoms, with statistical significance (P for nonlinearity <0.001).

LIMITATIONS

The present study employed a cross-sectional design, which precludes the establishment of causality. Furthermore, the data relied on self-reported measures.

CONCLUSIONS

In present study, moderate total flavonoids intake, but not high intake, was associated with lower odds of depressive symptoms suggesting a U-shaped association.

Hormonal and natural contraceptives: a review on efficacy and risks of different methods for an informed choice

The debate about contraception has become increasingly important as more and more people seek safe and effective contraception. More than 1 billion women of reproductive age worldwide need a method of family planning, and wellbeing, socio-economic status, culture, religion and more influence the reasons why a woman may ask for contraception. Different contraceptive methods exist, ranging from 'natural methods' (fertility awareness-based methods - FABMs) to barrier methods and hormonal contraceptives (HCs). Each method works on a different principle, with different effectiveness.FABMs and HCs are usually pitted against each other, although it's difficult to really compare them. FABMs are a valid alternative for women who cannot or do not want to use hormone therapy, although they may have a high failure rate if not used appropriately and require specific training. HCs are commonly used to address various clinical situations, although concerns about their possible side effects are still widespread. However, many data show that the appropriate use of HC has a low rate of adverse events, mainly related to personal predisposition.The aim of this review is to summarize the information on the efficacy and safety of FABMs and HCs to help clinicians and women choose the best contraceptive method for their needs.

Roflumilast ameliorates ovariectomy-induced depressive-like behavior in rats via activation of AMPK/mTOR/ULK1-dependent autophagy pathway

AIMS

Roflumilast, a well-known phosphodiesterase-4 (PDE-4) inhibitor, possess an anti-inflammatory activity with approved indications in chronic obstructive pulmonary disease. This study aimed to evaluate the neuroprotective role of roflumilast in ovariectomy (OVX)-induced depressive-like behavior in female rats and to shed light on a potential autophagy enhancing effect.

MAIN METHODS

Rats were randomly divided into four groups: sham, OVX, OVX + roflumilast (1 mg/kg, p.o), and OVX + roflumilast + chloroquine (CQ) (50 mg/kg, i.p). Drugs were administered for 4 weeks starting 2 weeks after OVX.

KEY FINDINGS

Roflumilast improved the depressive-like behaviors observed in OVX rats as evidenced by decreasing both forced swimming and open field immobility times while, increasing % sucrose preference and number of open field crossed squares. Histopathological analysis provides further evidence of roflumilast's beneficial effects, demonstrating that roflumilast ameliorated the neuronal damage caused by OVX. Roflumilast antidepressant potential was mediated via restoring hippocampal cAMP and BDNF levels as well as down-regulating PDE4 expression. Moreover, roflumilast revealed anti-inflammatory and anti-apoptotic effects via hindering TNF-α level and diminishing Bax/Bcl2 ratio. Roflumilast restored the autophagic function via up-regulation of p-AMPK, p-ULK1, Beclin-1 and LC3II/I expression, along with downregulation of P62 level and p-mTOR protein expression. The autophagy inhibitor CQ was used to demonstrate the suggested pathway.

SIGNIFICANCE

The present study revealed that roflumilast showed an anti-depressant activity in OVX female rats via turning on AMPK/mTOR/ULK1-dependent autophagy pathway; and neurotrophic, anti-inflammatory, and anti-apoptotic activities. Roflumilast could offer a more secure alternative to hormone replacement therapy for postmenopausal depression treatment.

Sex Differences in Depression and Anxiety

Depression and anxiety disorders carry a tremendous worldwide burden and emerge as a significant cause of disability among western societies. Both disorders are known to disproportionally affect women, as they are twice more likely to be diagnosed and moreover, they are also prone to suffer from female-specific mood disorders. Importantly, the prevalence of these affective disorders has notably risen after the COVID pandemic, especially in women. In this chapter, we describe factors that are possibly contributing to the expression of such sex differences in depression and anxiety. For this, we overview the effect of transcriptomic and genetic factors, the immune system, neuroendocrine aspects, and cognition. Furthermore, we also provide evidence of sex differences in antidepressant response and their causes. Finally, we emphasize the importance to consider sex as a biological variable in preclinical and clinical research, which may facilitate the discovery and development of new and more efficacious antidepressant and anxiolytic pharmacotherapies for both women and men.

The influence of hormonal contraception on depression and female sexuality: a narrative review of the literature

OBJECTIVE

Over the past decades, an increasing number of women have been using hormonal contraception. The potential role of sex hormones in regulating vegetative, psychophysiological, and cognitive functions has been highlighted in several studies, and there is a need to further understand the impact of hormonal contraception on women's quality of life, especially as regards psychological health and sexuality.

METHODS

We conducted a narrative review aimed at clarifying the mechanisms involved in the interaction between sex hormones and the brain, also focusing on the association between hormonal contraception and mood and sexual function.

RESULTS

Our findings clarified that hormonal contraception may be associated with depressive symptoms, especially among adolescents, and with sexual dysfunction. However, the evidence included in this review was conflicting and did not support the hypothesis that hormonal contraception directly causes depressive symptoms, major depressive disorder, or sexual dysfunction.

CONCLUSIONS

The optimal hormonal contraception should be identified in the context of shared decision making, considering the preferences and needs of each woman, as well as her physical and psychosexual conditions.

Antidepressant-like effects of acupuncture via modulation of corticosterone, sex hormones, and hippocampal BDNF expression in male rats

BACKGROUND

Post-weaning social isolated rodents exhibit pathophysiological changes associated with depression including adrenal axis hyperactivity, gonadal hormone level disturbances, molecular alterations in hippocampus, and immobility behavior in the forced swimming test (FST). Although acupuncture by absorbable thread implantation (acu-catgut, AC) elicits antidepressant-like effects in social isolated rats, AC effects on neuroendocrine and hippocampal molecular alterations have been less characterized.

OBJECTIVE

To investigate the participation of gonadal hormones, corticosterone, and brain-derived neurotrophic factor (BDNF) hippocampal expression, on the AC antidepressant-like effects in social isolated male rats.

METHODS

Sprague-Dawley male rats were raised in social isolation (SI) or standard conditions, for 11 weeks. AC (on Baihui (Du20), Yintang (E X-HN3), Shenshu (BL 23), Pishu (BL 20), Ganshu (BL 18), Xinshu (BL 15) and Guanyuan (Ren 4)), or Sham-AC (puncturing of acupoints without embedding the thread), was applied during the last three weeks of isolation period. Rats were evaluated in the FST; hormones plasmatic levels and hippocampal BDNF content were quantified by ELISA and Western blotting, respectively.

RESULTS

Social isolated rats showed more immobility in the FST and had lower testosterone and estradiol levels, higher corticosterone levels, and reduced hippocampal BDNF content than controls. BDNF level in hippocampus inversely correlated to depression-like behavior. AC but not sham-AC normalized immobility behavior, steroid hormone levels, and BDNF content, as in rats raised in a social environment.

CONCLUSIONS

AC antidepressant effect could be related to an improvement of hippocampal BDNF protein expression, as well as corticosterone and sex hormones disturbances associated with prolonged exposure to stress caused by social isolation. Present findings have implications for depression treatment in individuals early exposed to stress.

Increased risk of depression before and after unilateral or bilateral oophorectomy: A self-controlled case series study using a nationwide cohort in South Korea

BACKGROUND

There is insufficient evidence of the association between oophorectomy and depression.

METHODS

A nationwide medical records database of South Korea was used to investigate incidence rate ratios (IRRs) of major depressive disorder before and after oophorectomy (n = 36,284) using a self-controlled case series design. Outcomes before and after hysterectomy (n = 25,415) were identified to compare with those around oophorectomy.

RESULTS

In all oophorectomy and hysterectomy groups, the risk of depression was increased before and after surgery, peaking immediately before or after the operation, with no significant difference in the pattern of the results according to type of surgery. In the bilateral oophorectomy group, the IRR was increased between 2-3 months before the surgery, peaking immediately before surgery at 1.39 (95% CI: 1.30-1.49, p < .0001), and remained heightened for one-year postexposure. Subgroup analyses performed according to ovarian cancer, age group, and hormone replacement therapy produced results similar to those of the main outcome.

LIMITATIONS

Because we used claims data, the detailed clinical information related to oophorectomy is lacking. There is possibility that time-varying confounder besides age and season might have affected the results CONCLUSIONS: The risk of depression increased before and after oophorectomy. The increase in risk of depression started before oophorectomy and peaked immediately before or after the operation, but no significant differences between unilateral and bilateral surgery and cancer and noncancer or among age groups were noted.

Hormonal Contraception and Depression: Updated Evidence and Implications in Clinical Practice

Hormonal contraceptives are used worldwide by more than 100 million women. Some studies have been published about the possible appearance of depressive symptoms when using hormonal contraceptives, but this link is still a matter of debate. The purpose of this review is to provide an update of the literature on this issue, and to investigate the possible explanations of this problem based on animal and human studies. The main pathway responsible for menstrual cycle-related mood changes is the γ-aminobutyric acid pathway, which is sensitive to changes in the levels of progesterone and of its metabolites, the neurosteroids. In particular, allopregnanolone is a potentiating neurosteroid with anxiolytic and anti-convulsant effects whose levels change during a normal menstrual cycle together with progesterone levels. Progestins have different effects on allopregnanolone, mainly owing to their diverse androgenicity. Moreover, they might affect brain structure and function, even though the meaning of these changes has yet to be clarified. It is important to define the groups of women in which negative mood disorders are more likely to occur. Adolescence is a critical period and this age-specific vulnerability is complex and likely bidirectional. Moreover, women with a history of mood affective disorders or premenstrual dysphoric syndrome are at a higher risk when taking contraceptives. In this review, we aim to provide clinicians with advice on how to approach these difficult situations.

17β-Estradiol augments the neuroprotective effect of agomelatine in depressive- and anxiety-like behaviors in ovariectomized rats

RATIONALE AND OBJECTIVE

Estradiol decline has been associated with depression and anxiety in post-menopausal women. Agomelatine (Ago) is an agonist of the melatonergic MT1/MT2 receptors and an antagonist of the serotonergic 5-HT2c receptors. The present study aimed to evaluate the effects of combining Ago with 17β-estradiol (E2) on ovariectomy (OVX)-induced depressive- and anxiety-like behaviors in young adult female rats.

METHODS

OVX rats were treated with Ago (40 mg/kg/day, p.o.) for 10 days starting 1 week after surgery alone or combined with two doses of E2 (40 μg/kg/day, s.c.) given before behavioral testing.

RESULTS

Co-administration of E2 enhanced the anti-depressant and anxiolytics effects of Ago as evidenced by decreased immobility time in the forced swimming test, as well as increased time spent in the open arms and number of entries to open arms in the elevated plus-maze. In parallel, Ago increased hippocampal norepinephrine, dopamine, melatonin, and brain-derived neurotrophic factor (BDNF). Meanwhile, Ago-treated rats exhibited reduced hippocampal nuclear factor kappa beta (NF-kB) P65 expression and pro-inflammatory cytokine level. Ago upregulated estrogen receptor (ER α and β) mRNA expression in the hippocampus of OVX rats and elevated serum estradiol levels. Co-administration of E2 with Ago synergistically decreased NF-kB P65 expression and pro-inflammatory cytokines, and increased BDNF levels.

CONCLUSION

E2 augmented the neuroprotective effect of Ago in OVX rats via its anti-inflammatory and neurotrophic effects. The combined treatment of E2 and Ago should be further investigated as a treatment of choice for depression, anxiety, and sleep disturbances associated with menopause.

Effects of ketamine and other rapidly acting antidepressants on hippocampal excitatory and inhibitory transmission

A single sub-anesthetic intravascular dose of the use-dependent NMDAR antagonist, ketamine, improves mood in patients with treatment resistant depression within hours that can last for days, creating an entirely new treatment strategy for the most seriously ill patients. However, the psychomimetic effects and abuse potential of ketamine require that new therapies be developed that maintain the rapid antidepressant effects of ketamine without the unwanted side effects. This necessitates a detailed understanding of what cellular and synaptic mechanisms are immediately activated once ketamine reaches the brain that triggers the needed changes to elicit the improved behavior. Intense research has centered on the effects of ketamine, and the other rapidly acting antidepressants, on excitatory and inhibitory circuits in hippocampus and medial prefrontal cortex to determine common mechanisms, including key modifications in synaptic transmission and the precise location of the NMDARs that mediate the rapid and sustained antidepressant response. We review data comparing the effects of ketamine with other NMDAR receptor modulators and the muscarinic M1 acetylcholine receptor antagonist, scopolamine, together with evidence supporting the disinhibition hypothesis and the direct inhibition hypothesis of ketamine's mechanism of action on synaptic circuits using preclinical models.

A functional variant in the serotonin receptor 7 gene (HTR7), rs7905446, is associated with good response to SSRIs in bipolar and unipolar depression

Predicting antidepressant response has been a clinical challenge for mood disorder. Although several genome-wide association studies have suggested a number of genetic variants to be associated with antidepressant response, the sample sizes are small and the results are difficult to replicate. Previous animal studies have shown that knockout of the serotonin receptor 7 gene (HTR7) resulted in an antidepressant-like phenotype, suggesting it was important to antidepressant action. In this report, in the first stage, we used a cost-effective pooled-sequencing strategy to sequence the entire HTR7 gene and its regulatory regions to investigate the association of common variants in HTR7 and clinical response to four selective serotonin reuptake inhibitors (SSRIs: citalopram, paroxetine, fluoxetine and sertraline) in a retrospective cohort mainly consisting of subjects with bipolar disorder (n = 359). We found 80 single-nucleotide polymorphisms (SNPs) with false discovery rate < 0.05 associated with response to paroxetine. Among the significant SNPs, rs7905446 (T/G), which is located at the promoter region, also showed nominal significance (P < 0.05) in fluoxetine group. GG/TG genotypes for rs7905446 and female gender were associated with better response to two SSRIs (paroxetine and fluoxetine). In the second stage, we replicated this association in two independent prospective samples of SSRI-treated patients with major depressive disorder: the MARS (n = 253, P = 0.0169) and GENDEP studies (n = 432, P = 0.008). The GG/TG genotypes were consistently associated with response in all three samples. Functional study of rs7905446 showed greater activity of the G allele in regulating expression of HTR7. The G allele displayed higher luciferase activity in two neuronal-related cell lines, and estrogen treatment decreased the activity of only the G allele. Electrophoretic mobility shift assay suggested that the G allele interacted with CCAAT/enhancer-binding protein beta transcription factor (TF), while the T allele did not show any interaction with any TFs. Our results provided novel pharmacogenomic evidence to support the role of HTR7 in association with antidepressant response.

Investigating the potential role of BDNF and PRL genotypes on antidepressant response in depression patients: A prospective inception cohort study in treatment-free patients

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is associated with response to antidepressant drugs in mood and anxiety disorders. Prolactin (PRL) is a pituitary hormone with behavioural effects, acting as a neurotrophic factor within the brain and may be involved in antidepressant response.

OBJECTIVES

To investigate the relationship between BDNF and PRL genotypes with antidepressant drug response.

METHODS

Prospective inception cohort of 186 Russian treatment-free participants (28 men and 158 women) between 18 and 70 years clinically diagnosed with depressive disorder who initiated antidepressant medication. DNA polymorphisms were genotyped for PRL rs1341239, BDNF rs6265 and rs7124442. Primary outcome was measured by differences in Hamilton Depression Rating Scale (∆HAM-D) scores between baseline/week two, week two/week four, and baseline/week four. Linear regression and independent t-test determined the significance between polymorphisms and ∆HAM-D.

RESULTS

Comparisons between genotypes did not reveal any significant differences in scores during the first two weeks of treatment. In the latter two weeks, BDNF rs7124442 homozygous C patients responded significantly worse in comparison to homozygous T patients during this period. Further analysis within women and in post-menopausal women found a similar comparison between alleles.

LIMITATIONS

Study lasted four weeks, which may be considered short to associate genuine antidepressant effects.

CONCLUSIONS

Patients taking tricylic antidepressants were noted to have a significant improvement in ∆HAM-D compared to patients taking SSRIs. Homozygous C BDNF rs712442 patients were found to respond significantly worse in the last two weeks of treatment.

Venlafaxine Mitigates Depressive-Like Behavior in Ovariectomized Rats by Activating the EPO/EPOR/JAK2 Signaling Pathway and Increasing the Serum Estradiol Level

Reduced estradiol levels are associated with depression in women during the transition to and after menopause. A considerable number of studies focusing on the theme of treating depression through the activation of erythropoietin (EPO)-induced signaling pathways have been published. Venlafaxine is an approved antidepressant drug that inhibits both serotonin and norepinephrine transporters. The aim of the present study was to investigate the effects of venlafaxine on the depressive-like behaviors and serum estradiol levels in female rats following ovariectomy (OVX) and the possible roles of EPO-induced signaling pathways. Venlafaxine (10 mg/kg/day) was orally administered to OVX rats over a period of 4 weeks using two different treatment regimens: either starting 24 h or 2 weeks after OVX. Venlafaxine showed a superior efficacy in inducing antidepressant-like effects after an acute treatment (24 h post-OVX) than after the delayed treatment (2 weeks post-OVX) and was characterized by a decreased immobility time in the forced swimming test. In parallel, venlafaxine induced EPO and EPO receptor mRNA expression and increased levels of phospho-Janus kinase 2 (p-JAK2), phospho-signal transducer and activator of transcription 5, and phospho-extracellular signal-regulated kinase 1/2 in the hippocampus of OVX rats. Meanwhile, rats exhibited a marked reduction in the hippocampal Bax/Bcl2 ratio, caspase-3 activity, and tumor necrosis factor alpha levels after venlafaxine treatment. Venlafaxine also increased the hippocampal brain-derived neurotrophic factor and serum estradiol levels. Based on these findings, venlafaxine exerts a neuroprotective effect on OVX rats that is at least partially attributed to the activation of EPO/EPOR/JAK2 signaling pathways, anti-apoptotic activities, anti-inflammatory activities, and neurotrophic activities, as well as an increase in serum estradiol level. Graphical Abstract ᅟ.

Neuroendocrine Mechanisms Involved in Male Sexual and Emotional Behavior

OBJECTIVE

The aim of this narrative review was to analyze the role played by brain areas, neurohormones and neurotransmitters in the regulation of emotional and sexual behavior in the male.

METHODS

We analyzed the currently available literature dealing with brain structures, neurotransmitters and neurohormones involved in the regulation of emotional and sexual behavior in the male.

RESULTS

A common brain pathway is involved in these two aspects. The Hippocampus seems to control the signals coming from the external environment, while the amygdala and the hypothalamus control the response to social stimuli. Stimulation of amygdala in the animal models increases sexual performance, while it triggers violent emotional responses. Stimulation of the hypothalamus causes reactions of violent anger and increases sexual activity. Catecholaminergic stimulation of the amygdala and hypothalamus increases emotional and sexual behavior, while serotonin plays an inhibitory role. Cholinergic inhibition leads to a suppression of copulatory activity, while the animal becomes hyperemotive. Opioids, such as β-endorphin and met-enkephalin, reduce copulatory activity and induce impotence. Gonadal steroid hormones, such as estrogen in female and testosterone in male, which play a major role in the control of sexual behavior and gender difference have been highlighted in this review. Vasopressin, oxytocin and their receptors are expressed in high density in the "social behavior neural network" and play a role as signal system controlling social behavior. Finally, the neuropeptide kisspeptin and its receptors, located in the limbic structures, mediate olfactory control of the gonadotropic axis.

CONCLUSION

Further studies are needed to evaluate possible implications in the treatment of psychosexual and reproductive disorders.

Mesolimbic dopamine system and its modulation by vitamin D in a chronic mild stress model of depression in the rat

Depression, a common mood disorder, involves anhedonia and defects in reward circuits and mesolimbic dopamine transmission in the striatum and nucleus accumbens (NAc). Active vitamin-D, (1,25-(OH)₂ vitamin-D3), exerts protective and regulatory effects on the brain dopamine system. In this study, key depression-like symptoms were induced in rats by chronic mild-stress (CMS) and the comparative effect of treatment with 1,25-(OH)₂ vitamin-D3 (5, 10 μg/kg, or vehicle; i.p., twice weekly) or fluoxetine (5 mg/kg or vehicle, i.p., daily) on anhedonic behavior, locomotor activity and anxiety-like behavior was examined using sucrose preference test (SPT), open field test (OFT) and novel object exploration test (NOT), respectively. We also measured serum corticosterone levels and dopamine transporter-immunoreactivity (DAT-ir) levels in NAc shell and core. CMS exposure for 3 weeks was followed by a SPT and thereafter CMS was continued for 5 weeks, along with vitamin-D or fluoxetine treatment and further testing, which was concluded with another SPT. Vitamin-D treatment enhanced sucrose preference (P < 0.01; an hedonic effect) and increased object exploration (P < 0.01) in CMS rats. CMS significantly reduced the level of DAT-ir in NAc (P < 0.0001). Vitamin-D treatment restored/increased DAT-ir levels (P < 0.0001) in CMS rat NAc (core/ shell), compared to levels in fluoxetine treated and non-treated CMS rats. Vitamin-D did not alter locomotor activity or produce an anxiolytic effect in the OFT. These data suggest that similar to the antidepressant, fluoxetine, regular vitamin-D treatment can improve 'anhedonia-like symptoms' in rats subjected to CMS, probably by regulating the effect of dopamine-related actions in the NAc.

Intrinsic links among sex, emotion, and reproduction

Species survival is dependent on successful reproduction. This begins with a desire to mate, followed by selection of a partner, copulation and in monogamous mammals including humans, requires emotions and behaviours necessary to maintain partner bonds for the benefit of rearing young. Hormones are integral to all of these stages and not only mediate physiological and endocrine processes involved in reproduction, but also act as neuromodulators within limbic brain centres to facilitate the expression of innate emotions and behaviours required for reproduction. A significant body of work is unravelling the roles of several key hormones in the modulation of mood states and sexual behaviours; however, a full understanding of the integration of these intrinsic links among sexual and emotional brain circuits still eludes us. This review summarises the evidence to date and postulates future directions to identify potential psycho-neuroendocrine frameworks linking sexual and emotional brain processes with reproduction.

Evaluation of the potential antidepressant effects of soybean isoflavones

OBJECTIVE

The aim of the study was to determine whether isoflavones affect depressive symptoms in women.

METHODS

Literature searches were conducted to identify clinical and epidemiologic studies that evaluated the impact of soy intake and isoflavone exposure on depressive symptoms. References from identified studies were also evaluated to identify eligible studies.

RESULTS

Only limited epidemiologic research has evaluated the impact of soy or isoflavone intake on depression although several studies from China and Japan did find soy product intake was inversely related to risk of depression. Often times, soy was, however, evaluated only as a component of a summative dietary pattern (eg, a "Japanese" or "Healthy" diet). Of the 20 intervention studies identified, roughly half found statistically significant reductions in depressive symptoms in response to isoflavones although several had design weakness. Of those studies reporting a lack of antidepressant effects of isoflavones, design limitations likely contributed to the lack of efficacy. In all but two trials, assessment of depression was, however, a secondary outcome. It is notable that both trials in which depression was a primary outcome found isoflavones significantly improved symptoms.

CONCLUSIONS

Although the data are inconsistent and limited, the clinical and epidemiologic evidence suggests that isoflavones may offer a safe, well-tolerated option for management of depression. Furthermore, the intervention doses used in the clinical studies fall well within the dietary range. The extant literature reveals key design features for future studies, which based upon the results of this review, are clearly warranted.

The steroid metabolome in men with mood and anxiety disorders

The mood and behavior of individuals result from an orchestra of many factors. Among them steroids play an important role; however, only several common hormones have been investigated in this respect. It has been demonstrated that some steroid metabolites long considered merely the products of steroid hormone metabolism in fact possess considerable activity in the CNS. For this reason we studied the steroid metabolome including 50 analytes in 20 men with depression, 20 men with anxiety and 30 healthy controls. Significant differences were found not only between controls and men with either depression or anxiety, but also between men with depression and anxiety. Particularly striking were those steroids until now not generally associated with depression or anxiety, namely conjugated steroid forms, especially sulfates.

Differential effect of the 17β-aminoestrogens prolame, butolame and pentolame in anxiety and depression models in rats

Estrogens of clinical use produce consistent antidepressant- and anxiolytic-like effects in animal models of menopause. Regulation of the hypothalamic-pituitary-adrenal (HPA) or stress axis, has been proposed as a pathway through which estrogens improve affective-like behaviors. Anticoagulant 17β-aminoestrogens (17β-AEs) butolame and pentolame mimic some effects of estradiol (E2), i.e., on female rodent sexual behavior, with opposite actions on coagulation. However, their psychoactive actions have not been explored. On the basis of similitude with E2's effects, we hypothesized that these 17β-AEs would induce anxiolytic- and antidepressant-like effects, which would be reflected in a reduction of activity in the HPA axis. In ovariectomized female rats, chronic treatment with prolame (60 μg/kg), butolame (65 μg/kg) and pentolame (70 μg/kg) reduced anxiety-like behavior in the elevated plus maze (evidenced by an increase in time in open arms, E2 (40 μg/kg) +176%; prolame +201%; butolame, +237%; and pentolame +295%, in comparison to the control vehicle group 100%). Pentolame also decreased significantly anxiety-like behavior in the burying behavior test. Prolame and E2 produced a significantly antidepressant-like action, which was not induced by butolame and pentolame. Behavioral effects of 17β-AEs (and E2) on anxiety and depression did not follow the same pattern than corticosterone or E2 levels; they also were associated to changes in locomotor activity, evaluated by the open field test. These results constitute the first evidence of specific and selective actions of butolame and pentolame as anxiolytics for females with a hypoestrogenic condition. Results also confirm the potential of prolame as an antidepressant steroid with equivalent actions to E2. Psychoactive properties of 17β-AEs in combinations with reduced adverse effects on coagulation, suggest that 17β-AEs may be a good alternative replacement therapy for women with symptoms associated with menopause.

Coadministration of tramadol with aripiprazole and venlafaxine--The effect on spatial memory functions in male rats

BACKGROUND

The impairment of memory functions is very common in patients with chronic pain, particularly in patients with existing cognitive disorders. Results of some studies confirmed that tramadol (TRM), a frequently prescribed analgesic drug, improves memory functions in humans. However, there are no studies on the effect of co-administration of TRM with antidepressants or antipsychotics on memory; therefore, the aim of this study was to evaluate the effect of concomitant use of TRM with a second generation antipsychotic-aripiprazole (ARI) and an antidepressant-venlafaxine (VEN) on memory using an animal model.

METHODS

The effect of TRM (5mg/kg)+ARI (1.5mg/kg) and TRM (5mg/kg)+VEN (20mg/kg) on memory in Wistar rats was examined using the Morris water maze test after single and chronic administration (7 and 14 days).

RESULTS

It was observed that a single and chronic administration of TRM, VEN or ARI alone, but not a combination of TRM+VEN or TRM+ARI (except for 14 days of treatment) can improve memory in rats compared to the control group. After 14 days of administration, both combinations achieved improvement similar to each drug individually and improved spatial memory in rats compared to the control animals.

CONCLUSION

It can be assumed that chronic treatment with combinations of TRM+VEN or TRM+ARI is unlikely to cause memory impairment and interfere with either any antidepressant effect of VEN or any antipsychotic effect of ARI in patients suffering from chronic pain using TRM.

Sex differences in the chronic mild stress model of depression

A large volume of clinical and experimental evidence documents sex differences in brain anatomy, chemistry, and function, as well as in stress and drug responses. The chronic mild stress model (CMS) is one of the most extensively investigated animal models of chronic stress. However, only a limited number of studies have been conducted in female rodents despite the markedly higher prevalence of major depression among women. Herein, we review CMS studies conducted in rats and mice of both sexes and further discuss intriguing sex-dependent behavioral and neurobiological findings. The PubMed literature search engine was used to find and collect all relevant articles analyzed in this review. Specifically, a multitermed search was performed with 'chronic mild stress', 'chronic unpredictable stress' and 'chronic variable stress' as base terms and 'sex', 'gender', 'females' and 'depression' as secondary terms in various combinations. Male and female rodents appear to be differentially affected by CMS application, depending on the behavioral, physiological, and neurobiological indices that are being measured. Importantly, the CMS paradigm, despite its limitations, has been successfully used to assess a constellation of interdisciplinary research questions in the sex differences field and has served as a 'silver bullet' in assessing the role of sex in the neurobiology of major depression.

The Antidepressant-like Effects of Estrogen-mediated Ghrelin

Ghrelin, one of the brain-gut peptides, stimulates food-intake. Recently, ghrelin has also shown to play an important role in depression treatment. However, the mechanism of ghrelin's antidepressant-like actions is unknown. On the other hand, sex differences in depression, and the fluctuation of estrogens secretion have been proved to play a key role in depression. It has been reported that women have higher level of ghrelin expression, and ghrelin can stimulate estrogen secretion while estrogen acts as a positive feedback mechanism to up-regulate ghrelin level. Ghrelin may be a potential regulator of reproductive function, and estrogen may have additional effect in ghrelin's antidepressantlike actions. In this review, we summarize antidepressant-like effects of ghrelin and estrogen in basic and clinical studies, and provide new insight on ghrelin's effect in depression.

Drug-, dose- and sex-dependent effects of chronic fluoxetine, reboxetine and venlafaxine on open-field behavior and spatial memory in rats

In an effort to address the need to include both sexes in studies of effects of the SSRI fluoxetine, the NRI reboxetine and the SNRI venlafaxine on anxiety-related behavior and memory along with the use of chronic drug administration, male and female PVG/c rats were fed diets containing two doses of each drug for 21 days. The rats' anxiety level was then assessed in an open field. Short-term spatial memory for a brightness change in a Y maze was also measured. While there was little evidence of anxiolytic effects of any of the drugs, both fluoxetine and, to a lesser extent, venlafaxine appeared to be mainly anxiogenic in their action depending on both dose and sex. Reboxetine was relatively ineffective in this respect. Ability to locate the Y-maze arm that had changed (from white to black) seemed to be impaired for male (but not female) rats by both fluoxetine and venlafaxine and, to a much lesser extent, by reboxetine. Given the relative ineffectiveness of reboxetine in either test, it is possible that the effects of the other two drugs on both anxiety and memory were mainly due to their serotonin reuptake inhibiting properties. The differences that occurred between males and females in responsiveness to all three drugs supported the long-held view that both sexes should be investigated in studies of this sort, especially in view of reports of sex differences in effects of clinically prescribed antidepressants.

50 years of hormonal contraception-time to find out, what it does to our brain

Hormonal contraceptives are on the market for more than 50 years and used by 100 million women worldwide. However, while endogenous steroids have been convincingly associated with change in brain structure, function and cognitive performance, the effects of synthetic steroids contained in hormonal contraceptives on brain and cognition have barely been investigated. In this article we summarize the sparse findings, describing brain structural, functional and behavioral findings from the literature and suggest that synthetic steroids may contribute to masculinizing as well as feminizing effects on brain and behavior. We try to identify methodological challenges, explain, how results on endogenous steroids may transfer into research on hormonal contraceptives and point out factors that need to be controlled in the study of hormonal contraceptive dependent effects. We conclude that there is a strong need for more systematic studies, especially on brain structural, functional and cognitive changes due to hormonal contraceptive use. The hormonal contraceptive pill is the major tool for population control. Hence, such behavioral changes could cause a shift in society dynamics and should not stay unattended.

Acute but not sustained aromatase inhibition displays antidepressant properties

Aromatase inhibitors block the conversion of androgens to oestrogens and are used for the treatment of hormone-responsive breast cancer in menopause and recently also in premenopausal women. We investigate whether decreased oestrogen synthesis following aromatase inhibition leads to a depressive-like behavioural response in cycling female rats. Using the forced swim test (FST) we estimate the response of acute (three injections in 24 h) and sustained (7 d) letrozole and fluoxetine administration. Acute aromatase inhibition decreases immobility duration in the FST, indicating its antidepressant potential. Instead, sustained aromatase inhibition did not show such antidepressant potential. Testosterone elevation associates with the decreased depressive behaviour in the FST following acute letrozole treatment, but interestingly progesterone explains the increased swimming behaviour. Present findings may have potential implications for women treated with aromatase inhibitors, especially before menopause, as well as for the role of gonadal hormones in the expression of depressive symptoms and antidepressant response.

Mechanisms of pain modulation by sex hormones in migraine

A number of pain conditions, acute as well as chronic, are much more prevalent in women, such as temporomandibular disorder (TMD), irritable bowel syndrome, fibromyalgia, and migraine. The association of female sex steroids with these nociceptive conditions is well known, but the mechanisms of their effects on pain signaling are yet to be deciphered. We reviewed the mechanisms through which female sex steroids might influence the trigeminal nociceptive pathways with a focus on migraine. Sex steroid receptors are located in trigeminal circuits, providing the molecular substrate for direct effects. In addition to classical genomic effects, sex steroids exert rapid nongenomic actions to modulate nociceptive signaling. Although there are only a handful of studies that have directly addressed the effect of sex hormones in animal models of migraine, the putative mechanisms can be extrapolated from observations in animal models of other trigeminal pain disorders, like TMD. Sex hormones may regulate sensitization of trigeminal neurons by modulating expression of nociceptive mediator such as calcitonin gene-related peptide. Its expression is mostly positively regulated by estrogen, although a few studies also report an inverse relationship. Serotonin (5-Hydroxytryptamine [5-HT]) is a neurotransmitter implicated in migraine; its synthesis is enhanced in most parts of brain by estrogen, which increases expression of the rate-limiting enzyme tryptophan hydroxylase and decreases expression of the serotonin re-uptake transporter. Downstream signaling, including extracellular signal-regulated kinase activation, calcium-dependent mechanisms, and cAMP response element-binding activation, are thought to be the major signaling events affected by sex hormones. These findings need to be confirmed in migraine-specific animal models that may also provide clues to additional ion channels, neuropeptides, and intracellular signaling cascades that contribute to the increased prevalence of migraine in women.

Factors influencing behavior in the forced swim test

The forced swim test (FST) is a behavioral test in rodents which was developed in 1978 by Porsolt and colleagues as a model for predicting the clinical efficacy of antidepressant drugs. A modified version of the FST added the classification of active behaviors into swimming and climbing, in order to facilitate the differentiation between serotonergic and noradrenergic classes of antidepressant drugs. The FST is now widely used in basic research and the pharmaceutical screening of potential antidepressant treatments. It is also one of the most commonly used tests to assess depressive-like behavior in animal models. Despite the simplicity and sensitivity of the FST procedure, important differences even in baseline immobility rates have been reported between different groups, which complicate the comparison of results across studies. In spite of several methodological papers and reviews published on the FST, the need still exists for clarification of factors which can influence the procedure. While most recent reviews have focused on antidepressant effects observed with the FST, this one considers the methodological aspects of the procedure, aiming to summarize issues beyond antidepressant action in the FST. The previously published literature is analyzed for factors which are known to influence animal behavior in the FST. These include biological factors, such as strain, age, body weight, gender and individual differences between animals; influence of preconditioning before the FST: handling, social isolation or enriched environment, food manipulations, various kinds of stress, endocrine manipulations and surgery; schedule and routes of treatment, dosage and type of the drugs as well as experimental design and laboratory environmental effects. Consideration of these factors in planning experiments may result in more consistent FST results.

Estradiol reduces depressive-like behavior through inhibiting nitric oxide/cyclic GMP pathway in ovariectomized mice

Estradiol decline has been associated with depressive-like behavior in female mice and NO has been suggested to play a major role in the pathogenesis of major depression. This study was conducted to investigate the antidepressant-like effects of acute estradiol administration in female ovariectomized (OVX) mice and the possible role of nitric oxide (NO)/cyclic GMP (cGMP) pathway. To this end, bilateral ovariectomy was performed in female mice and different doses of estradiol were injected alone or in combination with non-specific NO synthase (NOS) inhibitor (L-NAME), selective neural NOS (nNOS) inhibitor (7-NI), an NO precursor (L-arginine) or selective phosphodiesterase type 5 inhibitor (sildenafil). The duration of immobility was recorded in the forced swimming test (FST) to assess the depressive behavior. Moreover, hippocampal levels of NO were determined in select groups. 10 days following the procedure, OVX mice showed significantly prolonged immobility time in comparison with the sham group. Estradiol (3, 10, and 30 μg/kg, s.c.), when injected 1 h prior to FST, exerted antidepressant-like effects in OVX mice. Both L-NAME (30 mg/kg, i.p.), and 7-NI (50 mg/kg, i.p.) significantly reduced the immobility times of OVX mice. Administration of a sub-effective dose of L-NAME (10mg/kg), 15 min after a sub-effective dose of estradiol (1 μg/kg, s.c.) had a robust antidepressant-like effect in OVX mice. Also a sub-effective dose of 7-NI (25 mg/kg), 30 min after a sub-effective dose of estradiol (1 μg/kg, s.c.) showed antidepressant-like effect in OVX mice. Both the NO precursor L-arginine (750 mg/kg, i.p.) and the cGMP-specific phosphodiesterase type 5 inhibitor sildenafil (5 mg/kg, i.p.), 30 min before estradiol treatment, prevented the antidepressant-like effect of a potent dose of estradiol (10 μg/kg, s.c.) in OVX mice. The present findings suggest that suppression of the NO synthase/NO/cGMP pathway may be involved in the antidepressant-like effects of estradiol in OVX mice.

The neurobiology of depression and antidepressant action

We present a comprehensive overview of the neurobiology of unipolar major depression and antidepressant drug action, integrating data from affective neuroscience, neuro- and psychopharmacology, neuroendocrinology, neuroanatomy, and molecular biology. We suggest that the problem of depression comprises three sub-problems: first episodes in people with low vulnerability ('simple' depressions), which are strongly stress-dependent; an increase in vulnerability and autonomy from stress that develops over episodes of depression (kindling); and factors that confer vulnerability to a first episode (a depressive diathesis). We describe key processes in the onset of a 'simple' depression and show that kindling and depressive diatheses reproduce many of the neurobiological features of depression. We also review the neurobiological mechanisms of antidepressant drug action, and show that resistance to antidepressant treatment is associated with genetic and other factors that are largely similar to those implicated in vulnerability to depression. We discuss the implications of these conclusions for the understanding and treatment of depression, and make some strategic recommendations for future research.

Upregulated mRNA levels of SERT, NET, MAOB, and BDNF in various brain regions of ovariectomized rats exposed to chronic aversive stimuli

Estrogen deficiency increases the risk of anxiety and mood disorders, presumably by deranging metabolism of the monoamine neurotransmitters and the expression of their reuptake transporters in the brain. Although estrogen-deficient individuals were also susceptible to stress, little was known regarding the effect of stress on the levels of transcripts related to brain monoamine metabolism. Herein, we used quantitative real-time PCR to quantify the mRNA levels of serotonin reuptake transporter (SERT), norepinephrine transporter (NET), monoamine oxidase-B (MAOB), tryptophan hydroxylase (TPH), and tyrosine hydroxylase (TH) in various brain regions of ovariectomized (OVX) rats which had been exposed for 4 weeks to chronic aversive stimuli (CAS), such as water deprivation, cage tilt, and illumination. We found that CAS induced stress responses in OVX rats as indicated by increases in the adrenal gland weight and sucrose intake. After CAS exposure, mRNA levels of SERT and NET were upregulated in the frontal cortex, hippocampus, amygdala, and periaqueductal gray. In addition, CAS also increased the mRNA levels of MAOB, an enzyme for dopamine degradation, in the same brain regions. However, CAS did not alter the mRNA levels of TPH or TH, both of which are rate-limiting enzymes for the synthesis of serotonin and norepinephrine in the dorsal raphé and locus coeruleus, respectively. Interestingly, mRNA expression of brain-derived neurotrophic factor precursor was upregulated in the hippocampus of CAS-exposed OVX rats, suggesting a compensatory mechanism which might counteract the stress-induced depression. Therefore, the present data have provided evidence to explain how stress affected brain monoamine metabolism in estrogen-deficient stressed patients.

Advances in tryptophan hydroxylase-2 gene expression regulation: new insights into serotonin-stress interaction and clinical implications

Serotonin (5-HT) modulates the stress response by interacting with the hormonal hypothalamic-pituitary-adrenal (HPA) axis and neuronal sympathetic nervous system (SNS). Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in 5-HT biosynthesis, and the recent identification of a second, neuron-specific TPH isoform (TPH2) opened up a new area of research. While TPH2 genetic variance has been linked to numerous behavioral traits and disorders, findings on TPH2 gene expression have not only reinforced, but also provided new insights into, the long-recognized but not yet fully understood 5-HT-stress interaction. In this review, we summarize advances in TPH2 expression regulation and its relevance to the stress response and clinical implications. Particularly, based on findings on rhesus monkey TPH2 genetics and other relevant literature, we propose that: (i) upon activation of adrenal cortisol secretion, the cortisol surge induces TPH2 expression and de novo 5-HT synthesis; (ii) the induced 5-HT in turn inhibits cortisol secretion by modulating the adrenal sensitivity to ACTH via the suprachiasmatic nuclei (SCN)-SNS-adrenal system, such that it contributes to the feedback inhibition of cortisol production; (iii) basal TPH2 expression or 5-HT synthesis, as well as early-life experience, influence basal cortisol primarily via the hormonal HPA axis; and (iv) 5'- and 3'-regulatory polymorphisms of TPH2 may differentially influence the stress response, presumably due to their differential roles in gene expression regulation. Our increasing knowledge of TPH2 expression regulation not only helps us better understand the 5-HT-stress interaction and the pathophysiology of neuropsychiatric disorders, but also provides new strategies for the treatment of stress-associated diseases.

Long-term ovariectomy modulates the antidepressant-like action of estrogens, but not of antidepressants

Controversial results related to effectiveness of estrogen replacement therapy (ERT) to alleviate depression are frequently reported. The discrepancies could be related to (a) time when ERT is initiated after the beginning of menopause and/or (b) type of estrogen used. Furthermore, estrogens modulate the antidepressant effect of different compounds; therefore, the effectiveness of antidepressant drugs could also depend on the menopausal status. The aim of the present study was to analyze whether the time after estrogen decline can influence antidepressant-like effects of two estrogens and/or two antidepressants. Thus, the antidepressant-like actions of 17β-estradiol (E(2)), 17α-ethynyl-estradiol (EE(2)), fluoxetine (FLX) and desipramine (DMI) were studied at different periods (1, 3 and 12 weeks) after ovariectomy (OVX), using the forced swimming test (FST). Results showed that OVX increased depressive-like behavior only 1 week after OVX. The antidepressant-like actions of E(2), but not those of EE(2), were cancelled 12 weeks after OVX. Conversely, antidepressant-like actions of FLX and DMI were observed at 1, 3 and 12 weeks after OVX. In conclusion, while the antidepressant-like effects of estrogens depended on the time at which treatment is initiated after OVX as well as on the estrogenic compound used, antidepressant-like effects of FLX and DMI were not blocked by OVX.

The importance of norepinephrine in depression

Depression is one of the most common psychological diseases with significant potential morbidity and mortality. Although the underlying pathophysiology of depression has not been clearly defined, preclinical and clinical evidence suggest disturbances in serotonin (5-HT), norepinephrine (NE), and dopamine (DA) neurotransmission in the central nervous system. Virtually all currently available antidepressants act on one or more of the following mechanisms: inhibition of reuptake of 5-HT or NE (and DA), antagonism of inhibitory presynaptic 5-HT or NE receptors, or inhibition of monoamine oxidase. All of these mechanisms result in an enhanced neurotransmission of 5-HT and/or NE. Evidence for the involvement of NE in depression is abundant, and recent studies on neuronal pathways and symptoms highlight the specific role of NE in this disorder. NE plays a determinant role in executive functioning regulating cognition, motivation, and intellect, which are fundamental in social relationships. Social dysfunction is possibly one of the most important factors affecting the quality of life in depressed patients.

Conjugated equine estrogen, with medroxyprogesterone acetate, enhances formation of 5alpha-reduced progestogens and reduces anxiety-like behavior of middle-aged rats

The mechanisms by which progestogens influence affective behaviors in females are poorly understood despite clear changes in mood/affect that are associated with their decline during menopause. Conjugated equine estrogens (CEE), with or without medroxyprogesterone acetate (MPA), are commonly prescribed hormone-replacement, but there is heterogeneity in responses to these pharmacotherapies. One way in which these compounds differ is in their capacity to potentiate metabolism of progesterone to its 5alpha-reduced products, dihydroprogesterone and 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP). This study investigated whether responses to CEE and MPA may be related to the capacity to metabolize progesterone. Middle-aged female rats that had maintained reproductive status, or those that had a decline, were administered vehicle, CEE and/or MPA. Effects on anxiety-like (open field, elevated plus maze) and social behaviors (social interaction test), and plasma and hippocampus steroid levels were determined. We hypothesized that CEE, but not MPA, would decrease anxiety-like behavior coincident with increased hippocampal metabolism of progesterone. CEE, or CEE+MPA, increased central entries in the open field and time spent on the open arms of the plus maze, but did not alter social interaction of rats that had maintained reproductive status. CEE and/or CEE+MPA increased E2 and 3alpha,5alpha-THP in plasma and/or hippocampus of rats, but MPA increased levels of dihydroprogesterone in the hippocampus of rats with declining reproductive status. Simple regressions showed that hippocampus 3alpha,5alpha-THP levels accounted for a significant proportion of the variance in anxiety-like behavior. Therefore, effects of CEE to reduce anxiety-like behavior of middle-aged rats may be owing, in part, to its capacity to enhance levels of 3alpha,5alpha-THP in the hippocampus.