Testosterone as well as estrogen increases serotonin2A receptor mRNA and binding site densities in the male rat brain

Recent advances in understanding adverse effects associated with drugs targeting the serotonin receptor, 5-HT GPCR

It has been acknowledged that more women suffer from adverse effects of drugs than men globally. A group of drugs targeting serotonin [5-hydroxytryptamine] (5-HT) binding G-protein-coupled receptors (GPCRs) have been reported to preferentially affect women more than men, causing adverse effects such as breast cancer and infertility. 5-HT GPCR-targeted drugs in the central nervous system (CNS) manage psychiatric conditions, such as depression or bipolar and in the peripheral nervous system (PNS) treat migraines. Physiological characteristics such as specific types of hormones, higher body fat density and smaller body mass in women result in disparities in pharmacodynamics of drugs, thus explaining sex-related differences in the observed adverse effects. In this review, we discuss the side effects of drugs targeting 5-HT GPCRs based on serotonin's roles in the CNS and PNS. We have systematically reviewed adverse effects of drugs targeting 5-HT GPCR using information from the Food and Drug Administration and European Medicines Agency. Further information on drug side effects and receptor targets was acquired from the SIDER and DrugBank databases, respectively. These drugs bind to 5-HT GPCRs in the CNS, namely the brain, and PNS such as breasts, ovaries and testes, potentially causing side effects within these areas. Oestrogen affects both the biosynthesis of 5-HT and the densities of 5-HT GPCRs in given tissues and cells. 5-HT GPCR-targeting drugs perturb this process. This is likely a reason why women are experiencing more adverse effects than men due to their periodic increase and the relatively high concentrations of oestrogen in women and, thus a greater incidence of the oestrogen-mediated 5-HT system interference. In addition, women have a lower concentration of serotonin relative to men and also have a relatively faster rate of serotonin metabolism which might be contributing to the former. We discuss potential approaches that could mitigate at least some of the adverse effects experienced by women taking the 5-HT GPCR-targeting drugs.

Therapeutic acute intermittent hypoxia: A translational roadmap for spinal cord injury and neuromuscular disease

We review progress towards greater mechanistic understanding and clinical translation of a strategy to improve respiratory and non-respiratory motor function in people with neuromuscular disorders, therapeutic acute intermittent hypoxia (tAIH). In 2016 and 2020, workshops to create and update a "road map to clinical translation" were held to help guide future research and development of tAIH to restore movement in people living with chronic, incomplete spinal cord injuries. After briefly discussing the pioneering, non-targeted basic research inspiring this novel therapeutic approach, we then summarize workshop recommendations, emphasizing critical knowledge gaps, priorities for future research effort, and steps needed to accelerate progress as we evaluate the potential of tAIH for routine clinical use. Highlighted areas include: 1) greater mechanistic understanding, particularly in non-respiratory motor systems; 2) optimization of tAIH protocols to maximize benefits; 3) identification of combinatorial treatments that amplify plasticity or remove plasticity constraints, including task-specific training; 4) identification of biomarkers for individuals most/least likely to benefit from tAIH; 5) assessment of long-term tAIH safety; and 6) development of a simple, safe and effective device to administer tAIH in clinical and home settings. Finally, we update ongoing clinical trials and recent investigations of tAIH in SCI and other clinical disorders that compromise motor function, including ALS, multiple sclerosis, and stroke.

In search of sex-related mediators of affective illness

Sex differences in the rates of affective disorders have been recognized for decades. Studies of physiologic sex-related differences in animals and humans, however, have generally yielded little in terms of explaining these differences. Furthermore, the significance of these findings is difficult to interpret given the dynamic, integrative, and highly context-dependent nature of human physiology. In this article, we provide an overview of the current literature on sex differences as they relate to mood disorders, organizing existing findings into five levels at which sex differences conceivably influence physiology relevant to affective states. These levels include the following: brain structure, network connectivity, signal transduction, transcription/translation, and epigenesis. We then evaluate the importance and limitations of this body of work, as well as offer perspectives on the future of research into sex differences. In creating this overview, we attempt to bring perspective to a body of research that is complex, poorly synthesized, and far from complete, as well as provide a theoretical framework for thinking about the role that sex differences ultimately play in affective regulation. Despite the overall gaps regarding both the underlying pathogenesis of affective illness and the role of sex-related factors in the development of affective disorders, it is evident that sex should be considered as an important contributor to alterations in neural function giving rise to susceptibility to and expression of depression.

Role of insulin-like growth factor 1, sex and corticosteroid hormones in male major depressive disorder

BACKGROUND

Hormones of the hypothalamic-pituitary-gonadal (HPG), hypothalamic-pituitary-adrenal (HPA), and hypothalamic-pituitary-somatotropic (HPS) axes are potentially involved in major depressive disorder (MDD), but these hormones have not been simultaneously investigated in male patients with MDD. We investigated the association between male MDD symptoms and estradiol, testosterone, cortisol, dehydroepiandrosterone sulfate (DHEAS), and insulin-like growth factor 1 (IGF1).

METHODS

Serum estradiol, testosterone, cortisol, DHEAS, and IGF1 levels were measured in 54 male patients with MDD and 37 male controls and were compared with clinical factors. We investigated the associations between hormone levels and Hamilton Depression Rating Scale (HAM-D) scores. The correlations among hormones were also investigated.

RESULTS

Patients had significantly lower estradiol levels than controls (22.4 ± 8.4 pg/mL vs. 26.1 ± 8.5 pg/mL, P = 0.040). Serum estradiol levels were negatively correlated with HAM-D scores (P = 0.000094) and positively correlated with Global Assessment of Functioning scores (P = 0.000299). IGF1 levels and the cortisol:DHEAS ratio were higher in patients than in controls (IGF1: 171.5 ± 61.8 ng/mL vs. 144.1 ± 39.2 ng/mL, P = 0.011; cortisol:DHEAS ratio: 0.07 ± 0.05 vs. 0.04 ± 0.02, P = 0.001). DHEAS levels were lower in patients than in controls (227.9 ± 108.4 μg/dL vs. 307.4 ± 131.2 μg/dL, P = 0.002). IGF1, cortisol:DHEAS ratio, and DHEAS were not significantly correlated with HAM-D scores. Cortisol and testosterone levels were not significantly different between patients and controls. Serum estradiol levels were positively correlated with DHEAS levels (P = 0.00062) in patients, but were not significantly correlated with DHEAS levels in controls.

CONCLUSION

Estradiol may affect the pathogenesis and severity of patients with MDD in men, and other hormones, such as those in the HPA and HPS axes, may also be involved in male MDD. Additionally, a correlation between estradiol and DHEAS may affect the pathology of MDD in men.

Influence of ovarian hormones on value-based decision-making systems: Contribution to sexual dimorphisms in mental disorders

Women and men exhibit differences in behavior when making value-based decisions. Various hypotheses have been proposed to explain these findings, stressing differences in functional lateralization of the brain, functional activation, neurotransmitter involvement and more recently, sex hormones. While a significant interaction of neurotransmitter systems and sex hormones has been shown for both sexes, decision-making in women might be particularly affected by variations of ovarian hormones. In this review we have gathered information from animal and human studies on how ovarian hormones affect decision-making processes in females by interacting with neurotransmitter systems at functionally relevant brain locations and thus modify the computation of decision aspects. We also review previous findings on impaired decision-making in animals and clinical populations with substance use disorder and depression, emphasizing how little we know about the role of ovarian hormones in aberrant decision-making.

The Role of Estrogen Receptors and Their Signaling across Psychiatric Disorders

Increasing evidence suggests estrogen and estrogen signaling pathway disturbances across psychiatric disorders. Estrogens are not only crucial in sexual maturation and reproduction but are also highly involved in a wide range of brain functions, such as cognition, memory, neurodevelopment, and neuroplasticity. To add more, the recent findings of its neuroprotective and anti-inflammatory effects have grown interested in investigating its potential therapeutic use to psychiatric disorders. In this review, we analyze the emerging literature on estrogen receptors and psychiatric disorders in cellular, preclinical, and clinical studies. Specifically, we discuss the contribution of estrogen receptor and estrogen signaling to cognition and neuroprotection via mediating multiple neural systems, such as dopaminergic, serotonergic, and glutamatergic systems. Then, we assess their disruptions and their potential implications for pathophysiologies in psychiatric disorders. Further, in this review, current treatment strategies involving estrogen and estrogen signaling are evaluated to suggest a future direction in identifying novel treatment strategies in psychiatric disorders.

Brain estrogen alters the effects of the antidepressant sertraline in middle-aged female and male mice

Estrogens are important in regulating mood, especially for females. However, whether tissue-specific estrogen, such as brain estrogen, contributes to the effects of antidepressant treatment has not been determined. The present study used middle-aged aromatase gene knockout (Ar^-/-) mice or overexpression (Thy1-Ar; hGFAP-Ar) mice as brain estrogen models to investigate whether brain estrogen synthesis alters the anti-depressive behaviors of sertraline treatment. Our results showed that depletion of brain estrogen increased depressive-like behavior in females, and elevated brain estrogen reduced depression-like behavior, regardless of sex. These genotype-related behaviors correlated with alterations of monoamine metabolism in the hippocampus (HPC) and the prefrontal cortex (PFC). We also demonstrated that male and female Ar^-/- mice exhibited an attenuation of sertraline-induced anti-depressive behaviors compared to wild-type (WT) mice. The present data suggest that brain estrogen alters depressive-like behaviors and changes the effectiveness of antidepressants in middle-aged mice, regardless of sex.

Hormonal Regulation of Mammalian Adult Neurogenesis: A Multifaceted Mechanism

Adult neurogenesis—resulting in adult-generated functioning, integrated neurons—is still one of the most captivating research areas of neuroplasticity. The addition of new neurons in adulthood follows a seemingly consistent multi-step process. These neurogenic stages include proliferation, differentiation, migration, maturation/survival, and integration of new neurons into the existing neuronal network. Most studies assessing the impact of exogenous (e.g., restraint stress) or endogenous (e.g., neurotrophins) factors on adult neurogenesis have focused on proliferation, survival, and neuronal differentiation. This review will discuss the multifaceted impact of hormones on these various stages of adult neurogenesis. Specifically, we will review the evidence for hormonal facilitation (via gonadal hormones), inhibition (via glucocorticoids), and neuroprotection (via recruitment of other neurochemicals such as neurotrophin and neuromodulators) on newly adult-generated neurons in the mammalian brain.

Albumin is a secret factor involved in multidirectional interactions among the serotoninergic, immune and endocrine systems that supervises the mechanism of CYP1A and CYP3A regulation in the liver

This review focuses on albumin, which is involved in multidirectional interactions among the immune, endocrine and serotoninergic systems and supervises the regulation of cytochrome P450 (CYP) isoforms under conditions of both normal liver function and liver insufficiency. Special attention is paid to albumin, thyroid hormones, testosterone and tryptophan hydroxylase in these interactions as well as their potential roles in liver regeneration. The association of these factors with inflammation and the modification of the mechanism of hepatic drug-metabolizing CYP isoform regulation are also presented because changes in the expression of CYP isoforms in the liver may result in subsequent changes to a marker substance used for testing CYP activity, thus providing a simple way to control the liver regeneration process or the dangerous stimulation of hepatocarcinogenesis.

Stress, sex hormones, inflammation, and major depressive disorder: Extending Social Signal Transduction Theory of Depression to account for sex differences in mood disorders

Social Signal Transduction Theory of Depression is a biologically plausible, multi-level theory that describes neural, physiologic, molecular, and genomic mechanisms that link experiences of social-environmental adversity with internal biological processes that drive depression pathogenesis, maintenance, and recurrence. Central to this theory is the hypothesis that interpersonal stressors involving social threat (e.g., social conflict, evaluation, rejection, isolation, and exclusion) upregulate inflammatory processes that can induce several depressive symptoms, including sad mood, anhedonia, fatigue, psychomotor retardation, and social-behavioral withdrawal. The original article describing this formulation (Psychol Bull 140:774-815, 2014) addressed critical questions involving depression onset and recurrence, as well as why depression is strongly predicted by early life stress and comorbid with anxiety disorders and certain physical disease conditions, such as asthma, rheumatoid arthritis, chronic pain, and cardiovascular disease. Here, we extend the theory to help explain sex differences in depression prevalence, which is a defining feature of this disorder. Central to this extension is research demonstrating that ovarian hormone fluctuations modulate women's susceptibility to stress, brain structure and function, and inflammatory activity and reactivity. These effects are evident at multiple levels and are highly context-dependent, varying as a function of several factors including sex, age, reproductive state, endogenous versus exogenous hormones, and hormone administration mode and dose. Together, these effects help explain why women are at greater risk for developing inflammation-related depressed mood and other neuropsychiatric, neurodevelopmental, and neurodegenerative disorders during the reproductive years, especially for those already at heightened risk for depression or in the midst of a hormonal transition period.

Identifying predictors of within-person variance in MRI-based brain volume estimates

Adequate reliability of measurement is a precondition for investigating individual differences and age-related changes in brain structure. One approach to improve reliability is to identify and control for variables that are predictive of within-person variance. To this end, we applied both classical statistical methods and machine-learning-inspired approaches to structural magnetic resonance imaging (sMRI) data of six participants aged 24-31 years gathered at 40-50 occasions distributed over 6-8 months from the Day2day study. We explored the within-person associations between 21 variables covering physiological, affective, social, and environmental factors and global measures of brain volume estimated by VBM8 and FreeSurfer. Time since the first scan was reliably associated with Freesurfer estimates of grey matter volume and total cortex volume, in line with a rate of annual brain volume shrinkage of about 1 percent. For the same two structural measures, time of day also emerged as a reliable predictor with an estimated diurnal volume decrease of, again, about 1 percent. Furthermore, we found weak predictive evidence for the number of steps taken on the previous day and testosterone levels. The results suggest a need to control for time-of-day effects in sMRI research. In particular, we recommend that researchers interested in assessing longitudinal change in the context of intervention studies or longitudinal panels make sure that, at each measurement occasion, (a) a given participant is measured at the same time of day; (b) all participants are measured at about the same time of day. Furthermore, the potential effects of physical activity, including moderate amounts of aerobic exercise, and testosterone levels on MRI-based measures of brain structure deserve further investigation.

Effects of Estrogens on Central Nervous System Neurotransmission: Implications for Sex Differences in Mental Disorders

Nearly one of every five US individuals aged 12 years old or older lives with certain types of mental disorders. Men are more likely to use various types of substances, while women tend to be more susceptible to mood disorders, addiction, and eating disorders, all of which are risks associated with suicidal attempts. Fundamental sex differences exist in multiple aspects of the functions and activities of neurotransmitter-mediated neural circuits in the central nervous system (CNS). Dysregulation of these neural circuits leads to various types of mental disorders. The potential mechanisms of sex differences in the CNS neural circuitry regulating mood, reward, and motivation are only beginning to be understood, although they have been largely attributed to the effects of sex hormones on CNS neurotransmission pathways. Understanding this topic is important for developing prevention and treatment of mental disorders that should be tailored differently for men and women. Studies using animal models have provided important insights into pathogenesis, mechanisms, and new therapeutic approaches of human diseases, but some concerns remain to be addressed. The purpose of this chapter is to integrate human and animal studies involving the effects of the sex hormones, estrogens, on CNS neurotransmission, reward processing, and associated mental disorders. We provide an overview of existing evidence for the physiological, behavioral, cellular, and molecular actions of estrogens in the context of controlling neurotransmission in the CNS circuits regulating mood, reward, and motivation and discuss related pathology that leads to mental disorders.

Sex differences and serotonergic mechanisms in the behavioural effects of psilocin

Psilocybin has recently attracted a great deal of attention as a clinical research and therapeutic tool. The aim of this paper is to bridge two major knowledge gaps regarding its behavioural pharmacology - sex differences and the underlying receptor mechanisms. We used psilocin (0.25, 1 and 4 mg/kg), an active metabolite of psilocybin, in two behavioural paradigms - the open-field test and prepulse inhibition (PPI) of the acoustic startle reaction. Sex differences were evaluated with respect to the phase of the female cycle. The contribution of serotonin receptors in the behavioural action was tested in male rats with selective serotonin receptor antagonists: 5-HT1A receptor antagonist (WAY100635 1 mg/kg), 5-HT2A receptor antagonist (MDL100907 0.5 mg/kg), 5-HT2B receptor antagonist (SB215505 1 mg/kg) and 5-HT2C receptor antagonist (SB242084 1 mg/kg). Psilocin induced dose-dependent inhibition of locomotion and suppression of normal behaviour in rats (behavioural serotonin syndrome, impaired PPI). The effects were more pronounced in male rats than in females. The inhibition of locomotion was normalized by 5-HT1A and 5-HT2B/C antagonists; however, PPI was not affected significantly by these antagonists. Our findings highlight an important issue of sex-specific reactions to psilocin and that apart from 5-HT2A-mediated effects 5-HT1A and 5-HT2C/B receptors also play an important role. These findings have implications for recent clinical trials.

Study of Sex Differences in Duloxetine Efficacy for Depression in Transgenic Mouse Models

Clinical evidences show sex differences in risk of developing depressive disorders as well as effect of antidepressants in depression treatment. However, whether such a sex-dependent risk of depression and efficacy of antidepressants is dependent on endogenous estrogen level remain elusive. The aim of this study is to explore the molecular mechanisms of sex differences in antidepressant duloxetine. In the present study, we used genetic knockout or overexpression estrogen-synthesizing enzyme aromatase (Ar) gene as models for endogenous estrogen deficiency and elevation endogenous estrogen, respectively, to examine the anti-depressive efficacy of duloxetine in males and females by force swimming test (FST). We also measured the sex-specific effect of duloxetine on dopamine and serotonin (5-HT) metabolisms in frontal cortex and hippocampus (HPC). Elevation of brain endogenous estrogen in male and female mice showed a reduction of immobility time in FST compared to control mice. Estrogen deficiency in females showed poor response to duloxetine treatment compared to sex-matched wildtype (WT) or aromatase transgenic mice. In contrast, male mice with estrogen deficiency showed same anti-depressive response to duloxetine treatments as aromatase transgenic mice. Our data showed that the sex different effect of endogenous estrogen on duloxetine-induced anti-depressive behavioral change is associated with brain region-specific changes of dopamine (DA) and 5-HT system. Endogenous estrogen exerts antidepressant effects in both males and females. Lacking of endogenous estrogen reduced antidepressive effect of duloxetine in females only. The endogenous estrogen level alters 5-HT system in female mainly, while both DA and 5-HT metabolisms were regulated by endogenous estrogen levels after duloxetine administration.

Nongenomic Actions of 17-β Estradiol Restore Respiratory Neuroplasticity in Young Ovariectomized Female Rats

Gonadal steroids modulate CNS plasticity, including phrenic long-term facilitation (pLTF), a form of spinal respiratory neuroplasticity resulting in increased phrenic nerve motor output following exposure to acute intermittent hypoxia (aIH; three 5 min episodes, 10.5% O₂). Despite the importance of respiratory system neuroplasticity, and its dependence on estrogen in males, little is known about pLTF expression or mechanisms of estrogen signaling in females. Here, we tested the hypotheses that (1) pLTF expression in young, gonadally intact female rats would be expressed during estrous cycle stages in which 17β-estradiol (E2) is naturally high (e.g., proestrus vs estrus), (2) pLTF would be absent in ovariectomized (OVX) rats and in physiological conditions in which serum progesterone, but not E2, is elevated (e.g., lactating rats, 3-10 d postpartum), and (3) acute E2 administration would be sufficient to restore pLTF in OVX rats. Recordings of phrenic nerve activity in female Sprague Dawley rats (3-4 months) revealed a direct correlation between serum E2 levels and pLTF expression in cycling female rats. pLTF was abolished with OVX, but was re-established by acute E2 replacement (3 h, intraperitoneal). To identify underlying E2 signaling mechanisms, we intrathecally applied BSA-conjugated E2 over the spinal phrenic motor nucleus and found that pLTF expression was restored within 15 min, suggesting nongenomic E2 effects at membrane estrogen receptors. These data are the first to investigate the role of ovarian E2 in young cycling females, and to identify a role for nongenomic estrogen signaling in any form of respiratory system neuroplasticity.SIGNIFICANCE STATEMENT Exposure to acute intermittent hypoxia induces phrenic long-term facilitation (pLTF), a form of spinal respiratory motor plasticity that improves breathing in models of spinal cord injury. Although pathways leading to pLTF are well studied in males and estradiol (E2) is known to be required, it has seldom been investigated in females, and underlying mechanisms of E2 signaling are unknown in either sex. We found that while ovariectomy abolished pLTF, it could be restored by acute systemic E2, or by intraspinal application of the membrane-impermeable E2 (BSA-conjugated E2; 15 min). The ability of nongenomic estrogen signaling within the cervical spinal cord to recover respiratory neuroplasticity in disorders of respiratory insufficiency suggests that membrane estrogen receptors may represent novel therapeutic targets to restore breathing in both sexes.

Hippocampal serotonin-2A receptor-immunoreactive neurons density increases after testosterone therapy in the gonadectomized male mice

The change of steroid levels may also exert different modulatory effects on the number and class of serotonin receptors present in the plasma membrane. The effects of chronic treatment of testosterone for anxiety were examined and expression of 5-HT_2A serotonergic receptor, neuron, astrocyte, and dark neuron density in the hippocampus of gonadectomized male mice was determined. Thirty-six adult male NMRI mice were randomly divided into six groups: intact-no testosterone treatment (No T), gonadectomy (GDX)-No T, GDX-Vehicle, GDX-6.25 mg/kg testosterone (T), GDX-12.5 mg/kg T, and GDX-25 mg/kg T. Anxiety-related behavior was evaluated using elevated plus maze apparatus. The animals were anesthetized after 48 hours after behavioral testing, and decapitated and micron slices were prepared for immunohistochemical as well as histopathological assessment. Subcutaneous injection of testosterone (25 mg/kg) may induce anxiogenic-like behavior in male mice. In addition, immunohistochemical data reveal reduced expression of 5-HT_2A serotonergic receptor after gonadectomy in all areas of the hippocampus. However, treatment with testosterone could increase the mean number of dark neurons as well as immunoreactive neurons in CA1 and CA3 area, dose dependently. The density of 5-HT_2A receptor-immunoreactive neurons may play a crucial role in the induction of anxiety like behavior. As reduction in such receptor expression have shown to significantly enhance anxiety behaviors. However, replacement of testosterone dose dependently enhances the number of 5-HT_2A receptor-immunoreactive neurons and interestingly also reduced anxiety like behaviors.

The time course of binocular rivalry during the phases of the menstrual cycle

Binocular rivalry occurs when markedly different inputs to the two eyes initiate alternations in perceptual dominance between the two eyes' views. A link between individual differences in perceptual dynamics of rivalry and concentrations of GABA, a prominent inhibitory neurotransmitter in the brain, has highlighted binocular rivalry as a potential tool to investigate inhibitory processes in the brain. The present experiment investigated whether previously reported fluctuations of GABA concentrations in a healthy menstrual cycle (Epperson et al., 2002) also are associated with measurable changes in rivalry dynamics within individuals. We obtained longitudinal measures of alternation rate, dominance, and mixture durations in 300 rivalry tracking blocks measured over 5 weeks from healthy female participants who monitored the start of the follicular and luteal phases of their cycle. Although we demonstrate robust and stable individual differences in rivalry dynamics, across analytic approaches and dependent measures, we found no significant change or even trends across menstrual phases in the temporal dynamics of dominance percepts. We found only sparse between-phase differences in skew and kurtosis on mixture percepts when data were pooled across sessions and blocks. These results suggest a complex dynamic between hormonal steroids, binocular rivalry, and GABAeric signaling in the brain and thus implicate the need to consider a systemic perspective when linking GABA with perceptual alternations in binocular rivalry.

Preclinical Abuse Potential Assessment of Flibanserin: Effects on Intracranial Self-Stimulation in Female and Male Rats

INTRODUCTION

Flibanserin is a serotonin receptor subtype 1A agonist and 2A antagonist that has been approved by the Food and Drug Administration for treating female sexual interest and arousal disorder. Little is known about the abuse potential of flibanserin.

AIM

To examine abuse-related effects of flibanserin in rats using an intracranial self-stimulation (ICSS) procedure previously used to evaluate the abuse potential of other drugs.

METHODS

Adult female and male Sprague-Dawley rats with electrodes implanted in the medial forebrain bundle were trained to press a lever for electrical brain stimulation under a "frequency-rate" ICSS procedure. In this procedure, increasing frequencies of brain stimulation maintain increasing rates of responding. Drugs of abuse typically increase (or "facilitate") ICSS rates and produce leftward and upward shifts in ICSS frequency-rate curves, whereas drugs that lack abuse potential typically do not alter or only decrease ICSS rates. Initial studies determined the potency and time course of effects on ICSS produced by acute flibanserin administration (1.0, 3.2 and 10.0 mg/kg). Subsequent studies determined the effects of flibanserin (3.2-18 mg/kg) before and after a regimen of repeated flibanserin administration (5.6 mg/kg/d for 5 days). Effects of the abused stimulant amphetamine (1.0 mg/kg) were examined as a positive control.

MAIN OUTCOME MEASURES

Flibanserin effects on ICSS frequency-rate curves in female and male rats were examined and compared with the effects of amphetamine.

RESULTS

Baseline ICSS frequency-rate curves were similar in female and male rats. Acute and repeated administrations of flibanserin produced only decreases in ICSS rates, and rate-decreasing effects of the highest flibanserin dose (10 mg/kg) were greater in female than in male rats. In contrast to flibanserin, amphetamine produced an abuse-related increase in ICSS rates that did not differ between female and male rats.

CONCLUSION

These results suggest that flibanserin has low abuse potential. In addition, this study suggests that female rats might be more sensitive than male rats to the rate-decreasing effects of high flibanserin doses.

Effects of aging on stress-related responses of serotonergic neurons in the dorsal raphe nucleus of male rats

Responses to various stressors in the brain change with age. However, little is known about the neural mechanisms underlying age-dependent changes in stress responses. It is known that serotonin, a stress-related transmitter, is closely related with the regulation of stress responses in the brain and that serotonergic function is modulated by various factors, including estrogen, in both sexes. In the present study, to elucidate the effects of aging on stress responses in serotonergic neurons, we examined the expression levels of tryptophan hydroxylase (TPH; a marker of serotonergic neurons) in the dorsal, ventral and lateral parts of the dorsal raphe nucleus (DRN) in young and old intact male rats. In young males, repeated restraint stress significantly increased the number of TPH-positive cells in all subdivisions of the DRN. In contrast, the stress-induced increase in TPH expression was only observed in the ventral part of the DRN in old males. Pretreatment with an estrogen receptor β antagonist had no effect on the number of TPH-positive cells in the dorsal and lateral DRN in young stressed males, whereas the antagonist decreased the number of TPH-positive cells in all DRN subdivisions in old stressed males. Our results suggest that the effects of repeated stress exposure on the expression of TPH in serotonergic neurons in the DRN change with age and that estrogenic effects via estrogen receptor β on TPH expression in stressed old males differ from those in young males.

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We examined the effect of aging on stress-induced TPH expression in male rats.

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The effect of stress exposure on TPH expression in the DRN changed with age.

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The effect of ER-β blockade on stress-induced TPH expression changed with age.

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Stress experience in young adulthood changed serotonergic response in old age.

Sex hormones affect neurotransmitters and shape the adult female brain during hormonal transition periods

Sex hormones have been implicated in neurite outgrowth, synaptogenesis, dendritic branching, myelination and other important mechanisms of neural plasticity. Here we review the evidence from animal experiments and human studies reporting interactions between sex hormones and the dominant neurotransmitters, such as serotonin, dopamine, GABA and glutamate. We provide an overview of accumulating data during physiological and pathological conditions and discuss currently conceptualized theories on how sex hormones potentially trigger neuroplasticity changes through these four neurochemical systems. Many brain regions have been demonstrated to express high densities for estrogen- and progesterone receptors, such as the amygdala, the hypothalamus, and the hippocampus. As the hippocampus is of particular relevance in the context of mediating structural plasticity in the adult brain, we put particular emphasis on what evidence could be gathered thus far that links differences in behavior, neurochemical patterns and hippocampal structure to a changing hormonal environment. Finally, we discuss how physiologically occurring hormonal transition periods in humans can be used to model how changes in sex hormones influence functional connectivity, neurotransmission and brain structure in vivo.

Functional and molecular neuroimaging of menopause and hormone replacement therapy

The level of gonadal hormones to which the female brain is exposed considerably changes across the menopausal transition, which in turn, is likely to be of great relevance for neurodegenerative diseases and psychiatric disorders. However, the neurobiological consequences of these hormone fluctuations and of hormone replacement therapy in the menopause have only begun to be understood. The present review summarizes the findings of thirty-five studies of human brain function, including functional magnetic resonance imaging, positron and single-photon computed emission tomography studies, in peri- and postmenopausal women treated with estrogen, or estrogen-progestagen replacement therapy. Seven studies using gonadotropin-releasing hormone agonist intervention as a model of hormonal withdrawal are also included. Cognitive paradigms are employed by the majority of studies evaluating the effect of unopposed estrogen or estrogen-progestagen treatment on peri- and postmenopausal women's brain. In randomized-controlled trials, estrogen treatment enhances activation of fronto-cingulate regions during cognitive functioning, though in many cases no difference in cognitive performance was present. Progestagens seems to counteract the effects of estrogens. Findings on cognitive functioning during acute ovarian hormone withdrawal suggest a decrease in activation of the left inferior frontal gyrus, thus essentially corroborating the findings in postmenopausal women. Studies of the cholinergic and serotonergic systems indicate these systems as biological mediators of hormonal influences on the brain. More, hormonal replacement appears to increase cerebral blood flow in several cortical regions. On the other hand, studies on emotion processing in postmenopausal women are lacking. These results call for well-powered randomized-controlled multi-modal prospective neuroimaging studies as well as investigation on the related molecular mechanisms of effects of menopausal hormonal variations on the brain.

Behavioral effects of social challenges and genomic mechanisms of social priming: What's testosterone got to do with it?

Social challenges from rival conspecifics are common in the lives of animals, and changes in an animal's social environment can influence physiology and behavior in ways that appear to be adaptive in the face of continued social instability (i.e. social priming). Recently, it has become clear that testosterone, long thought to be the primary mediator of these effects, may not always change in response to social challenges, an observation that highlights gaps in our understanding of the proximate mechanisms by which animals respond to their social environment. Here, our goal is to address the degree to which testosterone mediates organismal responses to social cues. To this end, we review the behavioral and physiological consequences of social challenges, as well as their underlying hormonal and gene regulatory mechanisms. We also present a new case study from a wild songbird, the dark-eyed junco (Junco hyemalis), in which we find largely divergent genome-wide transcriptional changes induced by social challenges and testosterone, respectively, in muscle and liver tissue. Our review underscores the diversity of mechanisms that link the dynamic social environment with an organisms' genomic, hormonal, and behavioral state. This diversity among species, and even among tissues within an organism, reveals new insights into the pattern and process by which evolution may alter proximate mechanisms of social priming.

Saliva testosterone and cortisol in male depressive syndrome, a community study. The Sudurnesjamenn Study

INTRODUCTION

The association between testosterone levels and depression is unclear. The relationship has been described as complex, i.e. more U (J)-shaped than linear in some previous studies.

AIM

The primary aim of this study was to examine the relationship between saliva testosterone level variations and different levels of male depressive symptoms in a community sample. The secondary aim was to investigate whether simultaneous testing of evening cortisol and testosterone improved the detection of depression.

METHODS

In a community study, 534 males were screened, using the Beck Depression Inventory (BDI), the Gotland Male Depression Scale (GMDS) and the Montgomery-Åsberg Depression Rating Scale (MADRS). Those with signs of depression (n = 65) and randomly selected controls (n = 69) had psychiatric evaluation for depressive disorder. In a sub-sample (n = 51) saliva testosterone was measured twice on a single day.

RESULTS

Testosterone morning values were significantly higher than evening values (236 vs. 145 pg/ml, P = 0.009). Evening testosterone was significantly higher in depressive males, according to both MADRS (P = 0.028) and BDI (P = 0.036). Having depression increased the likelihood of being in the highest third of testosterone levels (BDI P = 0.021; MADRS P = 0.018). Positive correlation was between total BDI score and elevated evening testosterone with and without psychotropics (P = 0.017; P = 0.002). Correlation was between elevated evening cortisol and evening testosterone levels (P = 0.021) though simultaneous testing did not increase specificity of detecting depression.

CONCLUSION

Evening saliva testosterone measurements seem the most informative, as they correlate with male depressive syndrome. Simultaneous testing for evening cortisol and evening testosterone levels did not increase specificity for clinical diagnosis of depressive disorder.

Hormone replacement with 17β-estradiol plus dihydrotestosterone restores male sexual behavior in rats treated neonatally with clomipramine

Male sexual behavior (MSB) in rodents, in both its consummatory and motivational components, is regulated by hormones such as testosterone, 17β-estradiol and 5-α-dihydrotestosterone. In experiments, neonatal treatment with clomipramine (CMI; a serotonin reuptake inhibitor) reproduces some of the signs of depression in adult age, including reduced sexual behavior manifested in a lower percentage of subjects that mount, intromit and ejaculate, although their testosterone levels were not altered. However, the effect of this treatment on estrogen levels and the consequences of hormone substitution using 17β-estradiol and 5-α-dihydrotestosterone on the expression of male sexual behavior are still unknown. Therefore, the objective of the present study was to analyze the effect of neonatal treatment with CMI on plasma testosterone and 17β-estradiol levels, and the role of testosterone, 17β-estradiol and 5-α-dihydrotestosterone in altering the consummatory and motivational components of sexual behavior in male rats. To this end, it analyzed the copulatory parameters and sexual incentive motivation (SIM) of rats treated with CMI under two conditions: basal and post-hormone replacements. Neonatal treatment with CMI did not affect plasma testosterone or 17β-estradiol concentrations, but did decrease both the consummatory component and sexual motivation according to the results of the SIM test. These aspects were recovered after administering 17β-estradiol +5-α-dihydrotestosterone, but not testosterone.

The influence of puberty on subcortical brain development

Puberty is characterized by hormonal, physical and psychological transformation. The human brain undergoes significant changes between childhood and adulthood, but little is known about how puberty influences its structural development. Using a longitudinal sample of 711 magnetic resonance imaging scans from 275 individuals aged 7–20 years, we examined how subcortical brain regions change in relation to puberty. Our regions of interest included the amygdala, hippocampus and corpus striatum including the nucleus accumbens (NA), caudate, putamen and globus pallidus (GP). Pubertal development was significantly related to structural volume in all six regions in both sexes. Pubertal development and age had both independent and interactive influences on volume for the amygdala, hippocampus and putamen in both sexes, and the caudate in females. There was an interactive puberty-by-age effect on volume for the NA and GP in both sexes, and the caudate in males. These findings suggest a significant role for puberty in structural brain development.

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Subcortical regions continue to develop through puberty in females and males.

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The developmental trajectories vary between subcortical regions.

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Puberty and age have independent and interactive influences on this development.

Testosterone alters genomic responses to song and monoaminergic innervation of auditory areas in a seasonally breeding songbird

Behavioral responses to social stimuli often vary according to endocrine state. Our previous work has suggested that such changes in behavior may be due in part to hormone-dependent sensory processing. In the auditory forebrain of female white-throated sparrows, expression of the immediate early gene ZENK (egr-1) is higher in response to conspecific song than to a control sound only when plasma estradiol reaches breeding-typical levels. Estradiol also increases the number of detectable noradrenergic neurons in the locus coeruleus and the density of noradrenergic and serotonergic fibers innervating auditory areas. We hypothesize, therefore, that reproductive hormones alter auditory responses by acting on monoaminergic systems. This possibility has not been examined in males. Here, we treated non-breeding male white-throated sparrows with testosterone to mimic breeding-typical levels and then exposed them to conspecific male song or frequency-matched tones. We observed selective ZENK responses in the caudomedial nidopallium only in the testosterone-treated males. Responses in another auditory area, the caudomedial mesopallium, were selective regardless of hormone treatment. Testosterone treatment reduced serotonergic fiber density in the auditory forebrain, thalamus, and midbrain, and although it increased the number of noradrenergic neurons detected in the locus coeruleus, it reduced noradrenergic fiber density in the auditory midbrain. Thus, whereas we previously reported that estradiol enhances monoaminergic innervation of the auditory pathway in females, we show here that testosterone decreases it in males. Mechanisms underlying testosterone-dependent selectivity of the ZENK response may differ from estradiol-dependent ones

Hormone replacement therapy and physical function in healthy older men. Time to talk hormones?

Improving physical function and mobility in a continuously expanding elderly population emerges as a high priority of medicine today. Muscle mass, strength/power, and maximal exercise capacity are major determinants of physical function, and all decline with aging. This contributes to the incidence of frailty and disability observed in older men. Furthermore, it facilitates the accumulation of body fat and development of insulin resistance. Muscle adaptation to exercise is strongly influenced by anabolic endocrine hormones and local load-sensitive autocrine/paracrine growth factors. GH, IGF-I, and testosterone (T) are directly involved in muscle adaptation to exercise because they promote muscle protein synthesis, whereas T and locally expressed IGF-I have been reported to activate muscle stem cells. Although exercise programs improve physical function, in the long-term most older men fail to comply. The GH/IGF-I axis and T levels decline markedly with aging, whereas accumulating evidence supports their indispensable role in maintaining physical function integrity. Several studies have reported that the administration of T improves lean body mass and maximal voluntary strength in healthy older men. On the other hand, most studies have shown that administration of GH alone failed to improve muscle strength despite amelioration of the detrimental somatic changes of aging. Both GH and T are anabolic agents that promote muscle protein synthesis and hypertrophy but work through separate mechanisms, and the combined administration of GH and T, albeit in only a few studies, has resulted in greater efficacy than either hormone alone. Although it is clear that this combined approach is effective, this review concludes that further studies are needed to assess the long-term efficacy and safety of combined hormone replacement therapy in older men before the medical rationale of prescribing hormone replacement therapy for combating the sarcopenia of aging can be established.

Different effects of scopolamine on learning, memory, and nitric oxide metabolite levels in hippocampal tissues of ovariectomized and Sham-operated rats

Different effects of scopolamine on learning, memory, and nitric oxide (NO) metabolites in hippocampal tissues of ovariectomized (OVX) and sham-operated rats were investigated. The animals in the Sham-Scopolamine (Sham-Sco) and OVX-Scopolamine (OVX-Sco) Groups were treated with 2 mg/kg scopolamine before undergoing the Morris water maze, while the animals in the Sham and OVX Groups received saline. The time latency and path length were significantly higher in both the Sham-Sco and the OVX-Sco Groups, in comparison with the Sham and OVX Groups, respectively (p<0.001). Significantly lower NO metabolite levels in the hippocampi of the Sham-Sco Group were observed, compared with the Sham Group (p<0.001), while there was no significant difference between the OVX-Sco and OVX Groups. The decreased NO level in the hippocampus may play a role in the learning and memory deficits induced by scopolamine. However, it seems that the effect of scopolamine on hippocampal NO differs between situations of presence and absence of ovarian hormones.

A review on the relationship between testosterone and the interpersonal/affective facet of psychopathy

Testosterone (T) has received increasing interest in the recent years as a probable biological determinant in the etiology of male-biased clinical conditions such as psychopathy (i.e. psychopathy is more prevalent in men and leads to an earlier onset and more severe expression of antisocial and aggressive behavior in men compared to women). In this review, the authors evaluated the potential relationship between T and different constructs closely related to the core characteristics of psychopathy (affective empathy, fear-reactivity, and instrumental aggression). After a thorough examination of the literature, it is concluded that high T exposure in utero and high circulating T levels throughout important life phases (most notably adolescence) or in response to social challenges (e.g. social stress, competition) could be an important etiological risk factor in the emergence of psychopathic behavior. Nevertheless, studies consistently indicate that high T is not related to a significantly reduced fear-reactivity and is only indirectly associated with the increased levels of instrumental aggression observed in psychopathic individuals. Therefore, psychopathy is likely to arise from an interaction between high T levels and other biological and socio-psychological risk factors, such as a constitutionally based dampened fear-reactivity, insecure/disordered attachment processes in childhood, and social discrimination/rejection in adolescence and/or adulthood.

Abnormally rapid reversal learning and reduced response to antipsychotic drugs following ovariectomy in female rats

Epidemiological and clinical life cycle studies indicate that favorable illness course and better response to antipsychotic drugs (APDs) in women with schizophrenia are positively correlated with estrogen levels. Accordingly, the estrogen hypothesis of schizophrenia proposes a neuroprotective role of estrogen in women vulnerable to schizophrenia. Previously we demonstrated in the rat that low levels of estrogen induced by ovariectomy led to disruption of latent inhibition (LI) reflecting impairment of selective attention, a core deficit of schizophrenia. LI disruption was reversed by 17β-estradiol and the atypical APD clozapine, whereas the typical APD haloperidol was ineffective unless co-administered with 17β-estradiol. Here we aimed to extend these findings by testing ovariectomized rats in another selective attention task, discrimination reversal. Ovariectomy led to a loss of selective attention as manifested in abnormally rapid reversal. The latter was normalized by high dose of 17β-estradiol (150 μg/kg) and clozapine (2.5mg/kg), but not by haloperidol (0.1mg/kg) or lower doses of 17β-estradiol (10 and 50 μg/kg). However, co-administration of haloperidol with 17β-estradiol (50 μg/kg) was effective. In sham rats low 17β-estradiol (10 μg/kg) produced rapid reversal, while high 17β-estradiol (150 μg/kg), haloperidol alone, or haloperidol-17β-estradiol combination reduced reversal speed. Clozapine did not affect reversal speed in sham rats. These results strengthen our previous results in suggesting that schizophrenia-like attentional abnormalities as well as reduced response to APDs in female rats are associated with low level of gonadal hormones. In addition, they support the possibility that estrogen may have an antipsychotic-like action in animal models.

Estrogen effects on the forced swim test differ in two outbred rat strains

Changes in reproductive hormones, such as estrogen, play a role in mood regulation. The present study examined strain differences (Long-Evans vs. Wistar-Hannover) in the behavioral and biochemical effects of estrogen manipulation. Adult ovariectomized female rats were treated with estradiol, vehicle, or withdrawn from estradiol. The two strains demonstrated differential behavioral responses to short-term estradiol administration in the forced swim test; estradiol induced an antidepressant-like effect in Long-Evans rats but not in Wistar rats. Conversely, withdrawal from estradiol resulted in a depressive-like state in the Wistar rats but not in the Long-Evans rats. Western blot analyses found no differences in estrogen receptors α and β within the hippocampus or the frontal cortex, two brain areas strongly implicated in affective disorders. These data demonstrate the importance of strain as a variable when interpreting behavioral effects of estrogen.

Partial androgen deficiency, depression, and testosterone supplementation in aging men

The aim of this review was to summarize current knowledge on the correlation between depressive symptoms with a syndrome called partial androgen deficiency of the aging male (PADAM) and on the potential benefits of testosterone (T) treatment on mood. Despite, the causative nature of the relationship between low T levels and depression is uncertain, many hypogonadal men suffer from depression and vice versa several depressed patients are affected by hypogonadism. Supplementation with testosterone failed to show sound evidence of effectiveness in the treatment of depression. Nevertheless, testosterone supplementation has proved to be effective on some domains significant for the quality of life of aged patients with PADAM (sexual function and cognitive functions, muscular strengths).

Turner syndrome and sexual differentiation of the brain: implications for understanding male-biased neurodevelopmental disorders

Turner syndrome (TS) is one of the most common sex chromosome abnormalities. Affected individuals often show a unique pattern of cognitive strengths and weaknesses and are at increased risk for a number of other neurodevelopmental conditions, many of which are more common in typical males than typical females (e.g., autism and attention-deficit hyperactivity disorder). This phenotype may reflect gonadal steroid deficiency, haploinsufficiency of X chromosome genes, failure to express parentally imprinted genes, and the uncovering of X chromosome mutations. Understanding the contribution of these different mechanisms to outcome has the potential to improve clinical care for individuals with TS and to better our understanding of the differential vulnerability to and expression of neurodevelopmental disorders in males and females. In this paper, we review what is currently known about cognition and brain development in individuals with TS, discuss underlying mechanisms and their relevance to understanding male-biased neurodevelopmental conditions, and suggest directions for future research.

Age, sex, and reproductive hormone effects on brain serotonin-1A and serotonin-2A receptor binding in a healthy population

There is a need for rigorous positron emission tomography (PET) and endocrine methods to address inconsistencies in the literature regarding age, sex, and reproductive hormone effects on central serotonin (5HT) 1A and 2A receptor binding potential (BP). Healthy subjects (n=71), aged 20-80 years, underwent 5HT1A and 2A receptor imaging using consecutive 90-min PET acquisitions with [(11)C]WAY100635 and [(18)F]altanserin. Logan graphical analysis was used to derive BP using atrophy-corrected distribution volume (V(T)) in prefrontal, mesiotemporal, occipital cortices, and raphe nucleus (5HT1A only). We used multivariate linear regression modeling to examine BP relationships with age, age(2), sex, and hormone concentrations, with post hoc regional significance set at p<0.008. There were small postsynaptic 5HT1A receptor BP increases with age and estradiol concentration in women (p=0.004-0.005) and a tendency for small 5HT1A receptor BP declines with age and free androgen index in men (p=0.05-0.06). Raphe 5HT1A receptor BP decreased 4.5% per decade of age (p=0.05), primarily in men. There was a trend for 15% receptor reductions in prefrontal cortical regions in women relative to men (post hoc p=0.03-0.10). The significant decline in 5HT2A receptor BP relative to age (8% per decade; p<0.001) was not related to sex or hormone concentrations. In conclusion, endocrine standardization minimized confounding introduced by endogenous hormonal fluctuations and reproductive stage and permitted us to detect small effects of sex, age, and endogenous sex steroid exposures upon 5HT1A binding. Reduced prefrontal cortical 5HT1A receptor BP in women vs men, but increased 5HT1A receptor BP with aging in women, may partially explain the increased susceptibility to affective disorders in women during their reproductive years that is mitigated in later life. 5HT1A receptor decreases with age in men might contribute to the known increased risk for suicide in men over age 75 years. Low hormone concentrations in adults <50 years of age may be associated with more extreme 5HT1A receptor BP values, but remains to be studied further. The 5HT2A receptor declines with age were not related to sex or hormone concentrations in this sample. Additional study in clinical populations is needed to further examine the affective role of sex-hormone-serotonin receptor relationships.

Genetic determinants of aggression and impulsivity in humans

Human aggression/impulsivity-related traits have a complex background that is greatly influenced by genetic and non-genetic factors. The relationship between aggression and anxiety is regulated by highly conserved brain regions including amygdala, which controls neural circuits triggering defensive, aggressive, or avoidant behavioral models. The dysfunction of neural circuits responsible for emotional control was shown to represent an etiological factor of violent behavior. In addition to the amygdala, these circuits also involve the anterior cingulated cortex and regions of the prefrontal cortex. Excessive reactivity in the amygdala coupled with inadequate prefrontal regulation serves to increase the likelihood of aggressive behavior. Developmental alterations in prefrontal-subcortical circuitry as well as neuromodulatory and hormonal abnormality appear to play a role. Imbalance in testosterone/serotonin and testosterone/cortisol ratios (e.g., increased testosterone levels and reduced cortisol levels) increases the propensity toward aggression because of reduced activation of the neural circuitry of impulse control and self-regulation. Serotonin facilitates prefrontal inhibition, and thus insufficient serotonergic activity can enhance aggression. Genetic predisposition to aggression appears to be deeply affected by the polymorphic genetic variants of the serotoninergic system that influences serotonin levels in the central and peripheral nervous system, biological effects of this hormone, and rate of serotonin production, synaptic release and degradation. Among these variants, functional polymorphisms in the monoamine oxidase A (MAOA) and serotonin transporter (5-HTT) may be of particular importance due to the relationship between these polymorphic variants and anatomical changes in the limbic system of aggressive people. Furthermore, functional variants of MAOA and 5-HTT are capable of mediating the influence of environmental factors on aggression-related traits. In this review, we consider genetic determinants of human aggression, with special emphasis on genes involved in serotonin and dopamine metabolism and function.

Cooperation of sex chromosomal genes and endocrine influences for hypothalamic sexual differentiation

There is little debate that mammalian sexual differentiation starts from the perspective of two primary sexes that correspond to differential sex chromosomes (X versus Y) that lead to individuals with sex typical characteristics. Sex steroid hormones account for most aspects of brain sexual differentiation, however, a growing literature has raised important questions about the role of sex chromosomal genes separate from sex steroid actions. Several important model animals are being used to address these issues and, in particular, they are taking advantage of molecular genetic approaches using different mouse strains. The current review examines the cooperation of genetic and endocrine influences from the perspective of behavioral and morphological hypothalamic sexual differentiation, first in adults and then in development. In the final analysis, there is an ongoing need to account for the influence of hormones in the context of underlying genetic circumstances and null hormone conditions.

Estrogens and men with schizophrenia: is there a case for adjunctive therapy?

Adjunctive use of estrogen therapy has been shown to be effective in enhancing the treatment of schizophrenia in women. In men, consideration of estrogen therapy has been impacted by concerns of feminising side effects, however, clinical trials of the use of estrogen in treating prostate cancer, bone density loss and even aggression and psychosis in dementia or traumatic brain injury, show this to be a safe and effective therapy. The current 14-day randomised placebo-controlled trial in 53 men with schizophrenia was conducted to evaluate the efficacy of 2 mg oral estradiol valerate as an adjunct to atypical antipsychotic treatment. Results demonstrated for estradiol participants a more rapid reduction in general psychopathology that occurred in the context of greater increases in serum estrogen levels and reductions in FSH and testosterone levels. Approximately 28% of estradiol participants did not achieve an increase (at least a 50% from baseline) in serum estrogen suggesting that further research is needed to refine the type, dose and administration route for estrogen therapy in men. Findings do, however, suggest further exploration of a therapeutic role for adjunctive estradiol treatment in men with schizophrenia is warranted.

Sex-dependent antipsychotic capacity of 17β-estradiol in the latent inhibition model: a typical antipsychotic drug in both sexes, atypical antipsychotic drug in males

The estrogen hypothesis of schizophrenia suggests that estrogen is a natural neuroprotector in women and that exogenous estrogen may have antipsychotic potential, but results of clinical studies have been inconsistent. We have recently shown using the latent inhibition (LI) model of schizophrenia that 17β-estradiol exerts antipsychotic activity in ovariectomized (OVX) rats. The present study sought to extend the characterization of the antipsychotic action of 17β-estradiol (10, 50 and 150 μg/kg) by testing its capacity to reverse amphetamine- and MK-801-induced LI aberrations in gonadally intact female and male rats. No-drug controls of both sexes showed LI, ie, reduced efficacy of a previously non-reinforced stimulus to gain behavioral control when paired with reinforcement, if conditioned with two but not five tone-shock pairings. In both sexes, amphetamine (1 mg/kg) and MK-801 (50 μg/kg) produced disruption (under weak conditioning) and persistence (under strong conditioning) of LI, modeling positive and negative/cognitive symptoms, respectively. 17β-estradiol at 50 and 150 μg/kg potentiated LI under strong conditioning and reversed amphetamine-induced LI disruption in both males and females, mimicking the action of typical and atypical antipsychotic drugs (APDs) in the LI model. 17β-estradiol also reversed MK-induced persistent LI, an effect mimicking atypical APDs and NMDA receptor enhancers, but this effect was observed in males and OVX females but not in intact females. These findings indicate that in the LI model, 17β-estradiol exerts a clear-cut antipsychotic activity in both sexes and, remarkably, is more efficacious in males and OVX females where it also exerts activity considered predictive of anti-negative/cognitive symptoms.

Endogenous plasma estradiol in healthy men is positively correlated with cerebral cortical serotonin 2A receptor binding

BACKGROUND

Sex-hormones influence brain function and are likely to play a role in the gender predisposition to mood and anxiety disorders. Acute fluctuations of sex-hormone levels including hormonal replacement therapy appear to affect serotonergic neurotransmission, but it is unknown if baseline levels affect serotonergic neurotransmission. This study was undertaken to examine if baseline levels of endogenous sex hormones are associated with cerebral serotonin 2A (5-HT(2A)) receptor binding in men.

METHODS

In a group of 72 healthy men (mean age 37.5 years ±17.4 SD, range 19.6-81.7) we studied the effect of plasma sex hormone levels on neocortical 5-HT(2A) receptor binding as imaged with [(18)F]altanserin PET. The effect of endogenous sex-hormone levels was evaluated by multiple linear regression analysis.

RESULTS

Mean neocortical 5-HT(2A) receptor binding was positively correlated with estradiol (p=0.0001), whereas no independent effects of testosterone could be demonstrated. Correction for other factors of importance for 5-HT(2A) receptor binding did not change the result. A voxel-based analysis suggested that there were no regional differences in the estradiol effect on cortical 5-HT(2A) receptor binding.

CONCLUSIONS

Our data show a positive correlation between endogenous plasma estradiol levels and cortical 5-HT(2A) receptor binding in healthy men, whereas, no independent effect of testosterone was demonstrated. We speculate that this association could be mediated through effects on gene transcription.

Sex differences in the effects of N,N-diethyllysergamide (LSD) on behavioural activity and prepulse inhibition

The aim of this study was to describe sex differences in the behavioural effects of N,N-diethyllysergamide (LSD) (locomotor activity and other behavioural repertoire in the open field) and its effects on sensorimotor gating in rats (prepulse inhibition (PPI) of the acoustic startle reaction). Three groups of animals were analysed: males, oestral and pro-oestral phase females (EP females), and metoestral and dioestral phase females (MD females). LSD (5, 50 and 200 microg/kg subcutaneously) attenuated locomotor activity and normal behavioural repertoire, and induced flat body posture, wet dog shakes and disrupted PPI. The most prominent behavioural findings of LSD were for LSD 200 microg/kg which suppressed almost all behavioural activity. LSD had mainly inhibitory locomotor effects in males and MD females, yet in EP female rats LSD increased locomotion during the second half of testing period. The main sex differences were observed in locomotor and exploratory behaviour. Both EP and MD females were less sensitive to hypolocomotor effects of LSD and had less pronounced thigmotaxis than males. Further EP females had increased rearing after LSD 5microg/kg. On the contrary although LSD disrupted PPI in males and MD female rats, EP females were protected from this disruptive effect. Thus, EP females seem to have a lower sensitivity to LSD behavioural actions.

Castration and training in a spatial task alter the number of immature neurons in the hippocampus of male mice

New neurons are generated in the granule cell layer of the dentate gyrus (GCL) throughout adulthood. This process is modulated by many environmental and neurochemical factors. We previously observed that castrated mice, compared to sham-operated mice, perform poorly in the delayed matching to place water-maze task (DMTP). In this study, we quantified the number of doublecortin expressing (DCX+) immature neurons and Ki-67 expressing (Ki-67+) proliferating progenitors in mice previously tested in a spatial DMTP task, a nonspatial DMTP, or that received equivalent amounts of handling only. Regardless of DMTP training experience, castration reduced immature neuron number in the GCL but had no effect on proliferating progenitors. Compared to handling only, visible DMTP training reduced the immature neuron number, but hidden DMTP training had no effect. Castration did not alter these environmental effects. Finally, performance on the spatial DMTP task did not correlate with immature neuron number. In addition, while the number of immature neurons was strongly reduced following cranial irradiation with (137)Cs, this treatment did not affect spatial DMTP performance. Thus, in mice, castration disrupts spatial memory and reduces immature neuron number, but there is no strong link between these effects.

Gender and the use of hormonal contraception in women are not associated with cerebral cortical 5-HT 2A receptor binding

Gender influences brain function including serotonergic neurotransmission, which may play a role in the well-known gender variations in vulnerability to mood and anxiety disorders. Even though hormonal replacement therapy in menopause is associated with globally increased cerebral 5-HT(2A) receptor binding it is not clear if gender or use of hormonal contraception exhibits associations with 5-HT(2A) receptor binding. We found no significant effect of gender on cortical 5-HT(2A) receptor binding (P=0.15, n=132). When adjusting for the personality trait neuroticism, known to be positively correlated to frontolimbic 5-HT(2A) receptor binding and to be more pronounced in women, again, the effect of gender was not significant (P=0.42, n=127). Also, the use of hormonal contraception (n=14) within the group of pre-menopausal women (total n=29) was not associated with cortical 5-HT(2A) receptor binding (P=0.31). In conclusion, neither gender, nor the use of hormonal contraception in premenopausal women was associated with cortical 5-HT(2A) receptor binding.

Partial androgen deficiency, depression and testosterone treatment in aging men

This study provides a critical review of the literature on depressive symptoms of partial androgen deficiency (PADAM) and their treatment with Testosterone (T). PADAM in aging males is responsible for a variety of behavioral symptoms, such as weakness, decreased libido and erectile dysfunction, lower psychological vitality, depressive mood, anxiety, insomnia, difficulty in concentrating, and memory impairment. The psychological and behavioural aspects of PADAM may overlap with signs and symptoms of major depression. Evidence of the relationship between androgen deficiency and male depression comes from studies that have assessed depression in hypogonadal subjects, the association between low T level and male depressive illness, and the antidepressant action of androgen replacement. The etiology of depressive symptoms of PADAM is multifactorial, and results from the interaction of the biological and psychosocial changes that take place during the mid-life transition. Although data derived from androgen treatment trials and androgen replacement do not support T treatment or replacement as more efficacious than placebo for major depressive disorder (MDD), the clinical impression is that, in some sub-threshold depressive syndromes, T may lead to antidepressant benefits.