Soy and social stress affect serotonin neurotransmission in primates

Diet, psychosocial stress, and Alzheimer's disease-related neuroanatomy in female nonhuman primates

INTRODUCTION

Associations between diet, psychosocial stress, and neurodegenerative disease, including Alzheimer's disease (AD), have been reported, but causal relationships are difficult to determine in human studies.

METHODS

We used structural magnetic resonance imaging in a well-validated non-human primate model of AD-like neuropathology to examine the longitudinal effects of diet (Mediterranean vs Western) and social subordination stress on brain anatomy, including global volumes, cortical thicknesses and volumes, and 20 individual regions of interest (ROIs).

RESULTS

Western diet resulted in greater cortical thicknesses, total brain volumes, and gray matter, and diminished cerebrospinal fluid and white matter volumes. Socially stressed subordinates had smaller whole brain volumes but larger ROIs relevant to AD than dominants.

DISCUSSION

The observation of increased size of AD-related brain areas is consistent with similar reports of mid-life volume increases predicting increased AD risk later in life. While the biological mechanisms underlying the findings require future investigation, these observations suggest that Western diet and psychosocial stress instigate pathologic changes that increase risk of AD-associated neuropathology, whereas the Mediterranean diet may protect the brain.

Role of Estradiol in the Expression of Genes Involved in Serotonin Neurotransmission: Implications for Female Depression

BACKGROUND

In women, changes in estrogen levels may increase the incidence and/or symptomatology of depression and affect the response to antidepressant treatments. Estrogen therapy in females may provide some mood benefits as a single treatment or might augment clinical response to antidepressants that inhibit serotonin reuptake.

OBJECTIVE

We analyzed the mechanisms of estradiol action involved in the regulation of gene expression that modulates serotonin neurotransmission implicated in depression.

METHOD

Publications were identified by a literature search on PubMed.

RESULTS

The participation of estradiol in depression may include regulation of the expression of tryptophan hydroxylase-2, monoamine oxidase A and B, serotonin transporter and serotonin-1A receptor. This effect is mediated by estradiol binding to intracellular estrogen receptor that interacts with estrogen response elements in the promoter sequences of tryptophan hydroxylase-2, serotonin transporter and monoamine oxidase-B. In addition to directly binding deoxyribonucleic acid, estrogen receptor can tether to other transcription factors, including activator protein 1, specificity protein 1, CCAAT/enhancer binding protein β and nuclear factor kappa B to regulate gene promoters that lack estrogen response elements, such as monoamine oxidase-A and serotonin 1A receptor.

CONCLUSION

Estradiol increases tryptophan hydroxylase-2 and serotonin transporter expression and decreases the expression of serotonin 1A receptor and monoamine oxidase A and B through the interaction with its intracellular receptors. The understanding of molecular mechanisms of estradiol regulation on the protein expression that modulates serotonin neurotransmission will be helpful for the development of new and more effective treatment for women with depression.

Impact of Tryptophan Depletion on Executive System Function during Menopause is Moderated by Childhood Adversity

Many healthy women with no history of cognitive dysfunction experience subjective executive difficulties during menopause. Preclinical literature suggests latent effects of early life adversity on serotonin function may play a role in this phenomenon. However, evidence in human participants regarding the mechanisms by which loss of estradiol contributes to this vulnerability is lacking. Here we examined the impact of tryptophan depletion (TD) and adverse childhood experiences (ACE) on brain activation during a working memory task in menopausal women. We hypothesized that an interactive effect between ACE and TD would be observed when women were hypogonadal, and that treatment with estradiol would attenuate this effect. Thirty-three women underwent functional imaging at four time points (123 total scans) in this double-blind, placebo controlled, cross-over study. The effects of TD, ACE, and TD × ACE were evaluated using a voxel-wise, mixed-effects, 2 × 2 ANOVA. In the absence of exogenous estradiol, a TD by ACE interaction was observed on BOLD signal in the right DLPFC such that TD increased activation in high ACE subjects but decreased activation in low ACE subjects. While a similar interaction was observed with placebo treatment, treatment with estradiol attenuated the effects of ACE and TD such that no between or within group differences were observed. Together, these results suggest that early life adversity may have a lasting impact on serotonergic circuits underlying executive function that are unmasked by loss of estradiol during menopause.

Impact of early life adversity and tryptophan depletion on functional connectivity in menopausal women: A double-blind, placebo-controlled crossover study

During the menopause transition, women are at increased risk of subjective symptoms of executive dysfunction. Evidence from animal and human participant studies suggests adverse childhood experiences (ACE) may be a risk factor for executive complaints during this hormonal transition. Preclinical literature indicates early life adversity effects on serotonin function may play a role in this increased susceptibility. However, the mechanisms underlying this increase in vulnerability in human participants remain relatively unknown. Here we examined the impact of ACE and tryptophan depletion (TD), a paradigm used to lower central serotonin levels, on functional network connectivity in discovery and replication datasets. We hypothesized that ACE would be associated with decreased within-network connectivity. We predicted that TD would further lower connectivity in women with high levels of early adversity, but have no effect in women with low levels of early adversity. Forty women underwent two functional imaging sequences at two time points (141 total scans) in a double-blind, placebo controlled, crossover study. The effects of ACE and TD were evaluated using generalized estimating equations (GEE). As predicted, ACE was associated with lower within-network connectivity. While TD had no effect on connectivity in the low ACE group, TD increased connectivity in the high ACE group. The robust effect of ACE remained significant in the replication dataset, though the ACE×TD interaction did not. Together, these results suggest that early life adversity has lasting impacts on large-scale functional networks underlying executive function. Alterations in functional network connectivity may be one mechanism by which early life adversity increases the risk of cognitive disorders during menopause.

Benefits of Hormone Therapy Estrogens Depend on Estrogen Type: 17β-Estradiol and Conjugated Equine Estrogens Have Differential Effects on Cognitive, Anxiety-Like, and Depressive-Like Behaviors and Increase Tryptophan Hydroxylase-2 mRNA Levels in Dorsal Raphe Nucleus Subregions

Decreased serotonin (5-HT) function is associated with numerous cognitive and affective disorders. Women are more vulnerable to these disorders and have a lower rate of 5-HT synthesis than men. Serotonergic neurons in the dorsal raphe nucleus (DRN) are a major source of 5-HT in the forebrain and play a critical role in regulation of stress-related disorders. In particular, polymorphisms of tryptophan hydroxylase-2 (TpH2, the brain-specific, rate-limiting enzyme for 5-HT biosynthesis) are implicated in cognitive and affective disorders. Administration of 17β-estradiol (E2), the most potent naturally circulating estrogen in women and rats, can have beneficial effects on cognitive, anxiety-like, and depressive-like behaviors. Moreover, E2 increases TpH2 mRNA in specific subregions of the DRN. Although conjugated equine estrogens (CEE) are a commonly prescribed estrogen component of hormone therapy in menopausal women, there is a marked gap in knowledge regarding how CEE affects these behaviors and the brain 5-HT system. Therefore, we compared the effects of CEE and E2 treatments on behavior and TpH2 mRNA. Female Sprague-Dawley rats were ovariectomized, administered either vehicle, CEE, or E2 and tested on a battery of cognitive, anxiety-like, and depressive-like behaviors. The brains of these animals were subsequently analyzed for TpH2 mRNA. Both CEE and E2 exerted beneficial behavioral effects, although efficacy depended on the distinct behavior and for cognition, on the task difficulty. Compared to CEE, E2 generally had more robust anxiolytic and antidepressant effects. E2 increased TpH2 mRNA in the caudal and mid DRN, corroborating previous findings. However, CEE increased TpH2 mRNA in the caudal and rostral, but not the mid, DRN, suggesting that distinct estrogens can have subregion-specific effects on TpH2 gene expression. We also found differential correlations between the level of TpH2 mRNA in specific DRN subregions and behavior, depending on the type of behavior. These distinct associations imply that cognition, anxiety-like, and depressive-like behaviors are modulated by unique serotonergic neurocircuitry, opening the possibility of novel avenues of targeted treatment for different types of cognitive and affective disorders.

Antidepressant-like effect of Ikwitang involves modulation of monoaminergic systems

Depression is a chronic mental disorder. Inflammatory reactions have an important function in the pathophysiology of depression. Ikwitang (IW) has been used to treat fever and inflammatory diseases, however, its effect on depression has not been previously investigated. Therefore, the present study evaluated the possible antidepressant‑like effect of IW using a forced swimming test (FST) in mice. IW was orally administered for 14 days. On the 14 day, IW was administered 1 h prior to the FST. The immobility durations of the IW groups (0.01, 0.1 and 1 g/kg) were significantly decreased, compared with those of the distilled water (D.W.) groups. The reduction of immobility duration by IW was associated with significant increases in the levels of serotonin, noradrenaline and estrogen receptor‑β in the brain. IW significantly increased the levels of brain‑derived neurotrophic factor and phosphorylated extracellular signal‑regulated kinases, compared with the D.W. groups. In addition, the levels of inflammatory cytokines were significantly reduced following IW administration in the hippocampus and serum. In conclusion, the results of the present study suggested that the antidepressant effect of IW may be associated with the modulation of monoaminergic systems and inflammatory reactions.

Dietary protein ingested before and during short photoperiods makes an impact on affect-related behaviours and plasma composition of amino acids in mice

In mammals, short photoperiod is associated with high depression- and anxiety-like behaviours with low levels of the brain serotonin and its precursor tryptophan (Trp). Because the brain Trp levels are regulated by its ratio to large neutral amino acids (Trp:LNAA) in circulation, this study elucidated whether diets of various protein sources that contain different Trp:LNAA affect depression- and anxiety-like behaviours in C57BL/6J mice under short-day conditions (SD). In the control mice on a casein diet, time spent in the central area in the open field test (OFT) was lower in the mice under SD than in those under long-day conditions (LD), indicating that SD exposure induces anxiety-like behaviour. The SD-induced anxiety-like behaviour was countered by an α-lactalbumin diet given under SD. In the mice that were on a gluten diet before transition to SD, the time spent in the central area in the OFT under SD was higher than that in the SD control mice. Alternatively, mice that ingested soya protein before the transition to SD had lower immobility in the forced swim test, a depression-like behaviour, compared with the SD control. Analysis of Trp:LNAA revealed lower Trp:LNAA in the SD control compared with the LD control, which was counteracted by an α-lactalbumin diet under SD. Furthermore, mice on gluten or soya protein diets before transition to SD exhibited high Trp:LNAA levels in plasma under SD. In conclusion, ingestion of specific proteins at different times relative to photoperiodic transition may modulate anxiety- and/or depression-like behaviours, partially through changes in plasma Trp:LNAA.

HIV Subtypes B and C gp120 and Methamphetamine Interaction: Dopaminergic System Implicates Differential Neuronal Toxicity

HIV subtypes or clades differentially induce HIV-associated neurocognitive disorders (HAND) and substance abuse is known to accelerate HIV disease progression. The HIV-1 envelope protein gp120 plays a major role in binding and budding in the central nervous system (CNS) and impacts dopaminergic functions. However, the mechanisms utilized by HIV-1 clades to exert differential effects and the methamphetamine (METH)-associated dopaminergic dysfunction are poorly understood. We hypothesized that clade B and C gp120 structural sequences, modeling based analysis, dopaminergic effect, and METH potentiate neuronal toxicity in astrocytes. We evaluated the effect of clade B and C gp120 and/or METH on the DRD-2, DAT, CaMKs and CREBP transcription. Both the structural sequence and modeling studies demonstrated that clade B gp120 in V1-V4, α -2 and N-glycosylated sites are distinct from clade C gp120. The distinct structure and sequence variation of clade B gp120 differentially impact DRD-2, DAT, CaMK II and CaMK IV mRNA, protein and intracellular expression compared to clade C gp120. However, CREB transcription is upregulated by both clade B and C gp120, and METH co-treatment potentiated these effects. In conclusion, distinct structural sequences of HIV-1 clade B and C gp120 differentially regulate the dopaminergic pathway and METH potentiates neurotoxicity.

Social inequalities in health in nonhuman primates

Overall health has been linked to socioeconomic status, with the gap between social strata increasing each year. Studying the impact of social position on health and biological functioning in nonhuman primates has allowed researchers to model the human condition while avoiding ethical complexities or other difficulties characteristic of human studies. Using female cynomolgus macaques (Macaca fascicularis), our lab has examined the link between social status and stress for 30 years. Female nonhuman primates are especially sensitive to social stressors which can deleteriously affect reproductive health, leading to harmful consequences to their overall health. Subordinates have lower progesterone concentrations during the luteal phase of menstrual cycle, which is indicative of absence or impairment of ovulation. Subordinate animals receive more aggression, less affiliative attention, and are more likely to exhibit depressive behaviors. They also express higher stress-related biomarkers such as increased heart rates and lower mean cortisol. While no differences in body weight between dominant and subordinate animals are observed, subordinates have lower bone density and more visceral fat than their dominant counterparts. The latter increases risk for developing inflammatory diseases. Differences are also observed in neurological and autonomic function. A growing body of data suggests that diet composition may amplify or diminish physiological stress responses which have deleterious effects on health. More experimental investigation of the health effects of diet pattern is needed to further elucidate these differences in an ongoing search to find realistic and long-term solutions to the declining health of individuals living across the ever widening socioeconomic spectrum.

Sertraline effects on cerebrospinal fluid monoamines and species-typical socioemotional behavior of female cynomolgus monkeys

RATIONALE

Although widely prescribed, little is known about the effects of selective serotonin reuptake inhibitors (SSRIs) on social behavior and cerebrospinal fluid (CSF) monoamines in female primates.

OBJECTIVE

The objective of this study was to determine the effects of sertraline on agonistic and affiliative behavior.

METHODS

Twenty-one adult female cynomolgus monkeys were housed in small, stable social groups, trained to participate in oral dosing, and began a 5-week cumulative dose-response study. Serial doses of 0, 5, 10, 15, and 20 mg/kg of sertraline were administered orally for 1 week each. Behavior was recorded daily during 10-min observations before and 4 h after dosing. On the seventh day of dosing, circulating sertraline/desmethylsertraline and CSF monoamines/metabolites were determined 4 h after the last dose.

RESULTS

At 20 mg/kg, circulating sertraline/desmethylsertraline was in the therapeutic range. CSF 5-hydroxyindole acetic acid decreased by 33 % (p < 0.05). Overall aggression, submission, locomotion, and time alone decreased, whereas affiliative behaviors (body contact, grooming) increased (all p values <0.05). Effects of sertraline on aggression and submission were social status-dependent, reducing aggression in dominants and submission in subordinates.

CONCLUSIONS

A clinically relevant oral dose of sertraline resulted in CSF metabolite changes similar to those observed in patients and altered the socioemotional behavior of female monkeys. Changes in CSF 5-HT and dopamine are novel observations that may be sex-specific. The robust effects of sertraline on aggression and affiliation may explain the efficacy of SSRIs on a range of human behavioral pathologies that share the characteristics of increased aggression and decreased sociality.

Immunoneuropathogenesis of HIV-1 clades B and C: role of redox expression and thiol modification

Previous studies have shown that, during infection, HIV-1 clade B and clade C differentially contribute to the neuropathogenesis and development of HIV-associated neurocognitive disorders (HANDs). The low-molecular-weight tripeptide glutathione (GSH) alters the redox balance and leads to the generation of reactive oxygen species, which play a significant role in the neuropathogenesis of HANDs. We hypothesized that the HIV-1 clade B and clade C viruses and their respective Tat proteins exert differential effects on monocyte-derived immature dendritic cells (IDCs) and neuroblastoma cells (SK-N-MC) by redox activation, which leads to immunoneuropathogenesis. The GSH/GSSG ratio and mRNA expression levels and protein modification of glutathione synthetase (GSS), glutathione peroxidase 1 (GPx1), superoxide dismutase 1 (SOD1), and catalase (CAT) were analyzed in IDCs infected with HIV-1 clade B or clade C as well as in cells treated with the respective Tat proteins. The results indicated that HIV-1 clade B virus and its Tat protein significantly increased the production of reactive oxygen species and reduced the GSH/GSSG ratio and subsequent downregulation of gene expression and protein modification of GSS, GPx1, SOD1, and CAT compared to infection with the clade C virus or treatment with the clade C Tat protein. Thus, our studies demonstrate that HIV-1 clades B and C exert differential effects of redox expression and thiol modification. HIV-1 clade B potentially induces oxidative stress, leading to more immunoneuropathogenesis than infection with HIV-1 clade C.

Estradiol and brain serotonin reuptake transporter in long-term ovariectomized parkinsonian monkeys

This study evaluated the effect of a one month 17β-estradiol treatment on brain serotonin (5-HT) reuptake transporter (SERT) in long-term ovariectomized (OVX) female monkeys (Macaca fascicularis) bearing a unilateral lesion with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) injected directly into the left substantia nigra modeling Parkinson disease (PD). Ovariectomy and MPTP lesion were performed four years before the estrogen treatment to model postmenopausal PD patients. SERT was measured by autoradiography using the radioligand [(3)H]Citalopram. Specific binding to SERT decreased in anterior cerebral cortex, nucleus accumbens, caudate nucleus and putamen on the lesioned side of 17β-estradiol and vehicle-treated monkeys compared to the intact side. In caudate nucleus and putamen the lesioned-induced decrease of [(3)H]Citalopram specific binding was more extensive in anterior and middle than posterior parts. [(3)H]Citalopram specific binding was increased in the cortex anterior cingulate gyrus of monkeys treated with 17β-estradiol in both brain hemispheres and was unchanged in the other brain regions investigated including the raphe nucleus. Positive correlations between [(3)H]Citalopram specific binding and 5-HT as well as 5-HIAA concentrations (reported previously) were obtained in the caudate nucleus and putamen and a negative correlation between SERT binding and 5-HIAA/5-HT concentration ratio suggesting MPTP lesion-induced 5-HT neuronal loss and lower 5-HT neurotransmission controlling and decreasing SERT for homeostasis. 17β-estradiol treatment initiated four years after ovariectomy of monkeys modeling hormonal conditions of post-menopause shows that SERT still displays some responsiveness to estrogens as observed in the anterior cingulate cortex. These results support a role of estrogens in 5-HT activity in PD.

Oestradiol modulation of serotonin reuptake transporter and serotonin metabolism in the brain of monkeys

Serotonin (5-hydroxytryptamine; 5-HT) is an important brain neurotransmitter that is implicated in mental and neurodegenerative diseases and is modulated by ovarian hormones. Nevertheless, the effect of oestrogens on 5-HT neurotransmission in the primate caudate nucleus, putamen and nucleus accumbens, which are major components of the basal ganglia, and the anterior cerebral cortex, mainly the frontal and cingulate gyrus, is not well documented. The present study evaluated 5-HT reuptake transporter (SERT) and 5-HT metabolism in these brain regions in response to 1-month treatment with 17β-oestradiol in short-term (1 month) ovariectomised (OVX) monkeys (Macaca fascicularis). SERT-specific binding was measured by autoradiography using the radioligand [³H]citalopram. Biogenic amine concentrations were quantified by high-performance liquid chromatography. 17β-Oestradiol increased SERT in the superior frontal cortex and in the anterior cingulate cortex, in the nucleus accumbens, and in subregions of the caudate nucleus of OVX monkeys. 17β-Oestradiol left [³H]citalopram-specific binding unchanged in the putamen, as well as the dorsal and medial raphe nucleus. 17β-Oestradiol treatment decreased striatal concentrations of the precursor of 5-HT, 5-hydroxytryptophan, and increased 5-HT, dopamine and 3-methoxytyramine concentrations in the nucleus accumbens, caudate nucleus and putamen, whereas the concentrations of the metabolites 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic acid and homovanillic acid remained unchanged. No effect of 17β-oestradiol treatment was observed for biogenic amine concentrations in the cortical regions. A significant positive correlation was observed between [³H]citalopram-specific binding and 5-HT concentrations in the caudate nucleus, putamen and nucleus accumbens, suggesting their link. These results have translational value for women with low oestrogen, such as those in surgical menopause or perimenopause.

A review on the relationship between testosterone and life-course persistent antisocial behavior

Life-course persistent antisocial behavior is 10 to 14 times more prevalent in males and it has been suggested that testosterone levels could account for this gender bias. Preliminary studies with measures of fetal testosterone find inconsistent associations with antisocial behavior, especially studies that use the 2D:4D ratio as a proxy for fetal testosterone. However, circulating testosterone consistently shows positive associations with antisocial behaviors throughout childhood, adolescence, and adulthood, particularly in males. It is suggested that high fetal/circulating testosterone interactively influence the maturation and functionality of mesolimbic dopaminergic circuitry, right orbitofrontal cortex, and cortico-subcortical connectivity, resulting in a strong reward motivation, low social sensitivity, and dampened regulation of strong motivational/emotional processes. The link between these testosterone induced endophenotypes and actual display of antisocial behavior is strongly modulated by different social (e.g., social rejection, low SES) and genetic (e.g., MAOA, 5HTT) risk factors that can disturb socio-, psycho-, and biological development and interact with testosterone in shaping behavior. When these additional risk factors are present, the testosterone induced endophenotypes may increase the risk for a chronic antisocial lifestyle. However, behavioral endophenotypes induced by testosterone can also predispose towards socially adaptive traits such as a strong achievement motivation, leadership, fair bargaining behaviors, and social assertiveness. These adaptive traits are more likely to emerge when the high testosterone individual has positive social experiences that promote prosocial behaviors such as strong and secure attachments with his caregivers, affiliation with prosocial peers, and sufficient socioeconomic resources. A theoretical model is presented, various hypotheses are examined, and future venues for research are discussed.

Chemopreventive potential of an ethyl acetate fraction from Curcuma longa is associated with upregulation of p57(kip2) and Rad9 in the PC-3M prostate cancer cell line

BACKGROUND

Turmeric (Curcuma longa) has been shown to possess anti-inflammatory, antioxidant and antitumor properties. However, despite the progress in research with C. longa, there is still a big lacuna in the information on the active principles and their molecular targets. More particularly very little is known about the role of cell cycle genes p57(kip2) and Rad9 during chemoprevention by turmeric and its derivatives especially in prostate cancer cell lines.

METHODS

Accordingly, in this study, we have examined the antitumor effect of several extracts of C. longa rhizomes by successive fractionation in clonogenic assays using highly metastatic PC-3M prostate cancer cell line.

RESULTS

A mixture of isopropyl alcohol: acetone: water: chloroform: and methanol extract of C. longa showed significant bioactivity. Further partition of this extract showed that bioactivity resides in the dichloromethane soluble fraction. Column chromatography of this fraction showed presence of biological activity only in ethyl acetate eluted fraction. HPLC, UV-Vis and Mass spectra studies showed presence three curcuminoids in this fraction besides few unidentified components.

CONCLUSIONS

From these observations it was concluded that the ethyl acetate fraction showed not only inhibition of colony forming ability of PC-3M cells but also up-regulated cell cycle genes p57(kip2) and Rad9 and further reduced the migration and invasive ability of prostate cancer cells.

Social subordination produces distinct stress-related phenotypes in female rhesus monkeys

Social subordination in female macaques is imposed by harassment and the threat of aggression and produces reduced control over one's social and physical environment and a dysregulation of the limbic-hypothalamic-pituitary-adrenal axis resembling that observed in people suffering from psychopathologies. These effects support the contention that this particular animal model is an ethologically relevant paradigm in which to investigate the etiology of stress-induced psychological illness related to women. Here, we sought to expand this model by performing a discriminate analysis (DA) on 33 variables within three domains; behavioral, metabolic/anthropomorphic, and neuroendocrine, collected from socially housed female rhesus monkeys in order to assess whether exposure to social subordination produces a distinct phenotype. A receiver operating characteristic (ROC) curve was also calculated to determine each domain's classification accuracy. DA found significant markers within each domain that differentiated dominant and subordinate females. Subordinate females received more aggression, showed more submissive behavior, and received less of affiliation from others than did dominant females. Metabolic differences included increased leptin, and reduced adiponectin in dominant compared to subordinate females. Dominant females exhibited increased sensitivity to hormonal stimulation with higher serum LH in response to estradiol, cortisol in response to ACTH, and increased glucocorticoid negative feedback. Serum oxytocin, CSF DOPAC and serum PACAP were all significantly higher in dominant females. ROC curve analysis accurately predicted social status in all three domains. Results suggest that socially house rhesus monkeys represent a cogent animal model in which to study the physiology and behavioral consequences of chronic psychosocial stress in humans.

Behavioral and neurobiological characteristics of social stress versus depression in nonhuman primates

The focus of the review is on the behavioral and physiological manifestations of stress versus depression. The purpose of the review is to evaluate the conceptual approach of using stress models as surrogates for depression. Social stress and depression have many characteristics in common and promote each other. Both have adverse effects on social relationships and the quality of life, and increase risk of other diseases. However, they are not the same constructs. In human and nonhuman primates, the behavior and neurobiology of stressed individuals differ from that of depressed individuals. Some similarities in stress physiology in socially stressed and depressed individuals have been used to support the use of stressed animals as models of depression, and much has been learned from stress models of depression. However, the studies reviewed here also suggest that the depressed state also has different characteristics than the stressed state, and studying the differences may be important to furthering our understanding of each of these constructs as well as their mutual relationship.

[Effects of Chinese herbal medicines for regulating liver qi on expression of 5-hydroxytryptamine 3B receptor in hypothalamic tissues of rats with anger emotion]

OBJECTIVE

To explore the central mechanisms of anger emotion and the effects of Chinese herbal medicines for regulating liver qi on the anger emotion and the expression level of 5-hydroxytryptamine 3B receptor (5-HT3BR) in rat hypothalamus.

METHODS

Rat models of anger-in or anger-out emotions were prepared by the methods of resident intruder paradigm. There were five groups in this study: control, anger-in model, Jingqianshu Granule-treated anger-in, anger-out model and Jingqianping Granule-treated anger-out groups. The treatment groups were orally given Jingqianshu granules and Jingqianping granules respectively, and the model groups and the normal control group were given sterile water. Open-field test and sucrose preference test were used to evaluate behavioristics of the rats. Semi-quantitative reverse transcription-polymerase chain reaction and Western blot methods were used to detect the expression levels of 5-HT3BR mRNA and protein in the rat hypothalamus.

RESULTS

The expression of 5-HT3BR in hypothalamus of anger-in model rats increased obviously (P<0.01) and that of anger-out model rats decreased obviously (P<0.01) compared with the normal control group. Compared with the model group, the expressions of 5-HT3BR in the treatment groups were significantly improved (P<0.01) after treatment, and recovered to normal level.

CONCLUSION

The anger-in stimulation obviously increases hypothalamic 5-HT3BR expression and the anger-out emotion can obviously reduce its expression. Chinese herbal medicines for regulating liver qi may treat anger emotion in rats by improving the hypothalamic 5-HT3BR protein and gene expression levels.

Human immunodeficiency virus type 1 clade B and C gp120 differentially induce neurotoxin arachidonic acid in human astrocytes: implications for neuroAIDS

HIV-1 clades (subtypes) differentially contribute to the neuropathogenesis of HIV-associated dementia (HAD) in neuroAIDS. HIV-1 envelop protein, gp120, plays a major role in neuronal function. It is not well understood how these HIV-1 clades exert these neuropathogenic differences. The N-methyl-D: -aspartate (NMDA) receptor-reduced glutamine synthesis could lead to secretion of neurotoxins such as arachidonic acid (AA) which plays a significant role in the neuropathogenic mechanisms in neuroAIDS. We hypothesize that clade B and C gp120 proteins exert differential effects on human primary astrocytes by production of the neurotoxin arachidonic acid. Our results indicate that clade B gp120 significantly downregulated NMDA receptor gene and protein expression, and level of glutamine while increasing expression of prostaglandin E2 (PGE(2)) and thromboxane A2 receptor (TBXA(2) R) compared to HIV-1 clade C gp120 protein. Thus, our studies for the first time demonstrate that HIV-1 clade B-gp120 protein appears to induce higher levels of expression of the neuropathogenic molecule cyclooxygenase-2 (COX-2)-mediated arachidonic acid by-products, PGE(2), and TBXA(2) R compared to HIV-1 clade C gp120 protein. These studies suggest that HIV-1 clade B and C gp120 proteins may play a differential role in the neuropathogenesis of HAD in neuroAIDS.

Human immunodeficiency virus type 1 clade B and C Tat differentially induce indoleamine 2,3-dioxygenase and serotonin in immature dendritic cells: Implications for neuroAIDS

Human immunodeficiency virus type 1 (HIV-1) is commonly associated with immune dysfunctions and the suppression of antigen-presenting cells. This results in immune alterations, which could lead to impaired neuronal functions, such as neuroAIDS. The neurotoxic factor kynurenine (KYN), the rate-limiting enzyme indoleamine 2,3-dioxygenase (IDO), serotonin (5-HT), and serotonin transporter (5-HTT) may play a role in tryptophan deficiency and serotogenic dysfunction in neuroAIDS. HIV-1 transactivator regulatory protein (Tat) is known to play a major role in immune dysfunction. Previous studies suggest that HIV-1 B and C clades differentially manifest neuronal dysfunctions in the infected host. In the present study we examine the effect of HIV-1 B and C clade-derived Tat on IDO and 5-HTT gene and protein expressions by dendritic cells as studied by quantitative polymerase chain reaction (qPCR) and Western blot. In addition, the intracellular IDO expression, IDO enzyme activity, and the levels of 5-HT and KYN were also measured. Results indicate that HIV-1 clade B Tat up-regulates IDO and down-regulates 5-HTT gene and protein expressions. Further, HIV-1 clade B Tat caused a reduction of 5-HT with simultaneous increase in KYN levels as compared to HIV-1 clade C Tat. These studies suggest that HIV-1 clade B and C Tat proteins may play a differential role in the neuropathogenesis of HIV-associated dementia (HAD) or HIV-associated neurocognitive disorder (HAND).

Estrogen receptor beta regulates the expression of tryptophan-hydroxylase 2 mRNA within serotonergic neurons of the rat dorsal raphe nuclei

Dysfunctions of the brain 5-HT system are often associated with affective disorders, such as depression. The raphe nuclei target the limbic system and most forebrain areas and constitute the main source of 5-HT in the brain. All 5-HT neurons express tryptophan hydroxylase-2 (TPH2), the brain specific, rate-limiting enzyme for 5-HT synthesis. Estrogen receptor (ER) beta agonists have been shown to attenuate anxiety- and despair-like behaviors in rodent models. Therefore, we tested the hypothesis that ER beta may contribute to the regulation of gene expression in 5-HT neurons of the dorsal raphe nuclei (DRN) by examining the effects of systemic and local application of the selective ER beta agonist diarylpropionitrile (DPN) on tph2 mRNA expression. Ovariectomized (OVX) female rats were injected s.c. with DPN or vehicle once daily for 8 days. In situ hybridization revealed that systemic DPN-treatment elevated basal tph2 mRNA expression in the caudal and mid-dorsal DRN. Behavioral testing of all animals in the open field (OF) and on the elevated plus maze (EPM) on days 6 and 7 of treatment confirmed the anxiolytic nature of ER beta activation. Another cohort of female OVX rats was stereotaxically implanted bilaterally with hormone-containing wax pellets flanking the DRN. Pellets contained 17-beta-estradiol (E), DPN, or no hormone. Both DPN and E significantly enhanced tph2 mRNA expression in the mid-dorsal DRN. DPN also increased tph2 mRNA in the caudal DRN. DPN- and E-treated rats displayed a more active stress-coping behavior in the forced-swim test (FST). No behavioral differences were found in the OF or on the EPM. These data indicate that ER beta acts at the level of the rat DRN to modulate tph2 mRNA expression and thereby influence 5-HT synthesis in DRN subregions. Our results also suggest that local activation of ER beta neurons in the DRN may be sufficient to decrease despair-like behavior, but not anxiolytic behaviors.

Differential regulation of indoleamine-2,3-dioxygenase (IDO) by HIV type 1 clade B and C Tat protein

Previous studies have demonstrated that infection with HIV-1 clades might differentially contribute to the neuropathogenesis of HIV-1-associated dementia (HAD). HIV-1 transactivator regulatory protein (Tat) plays a major role in the process of disruption of neuronal function. It is not well understood how these HIV-1 subtypes exert different neuropathogenic effects. Activation of indoleamine-2,3-dioxygenase (IDO), the rate-limiting enzyme of the kynurenine pathway, leads to increased tryptophan catabolism and the generation of neurotoxins such as kynurenine (KYN). It is known that KYN plays a crucial role in the neuropathogenesis of HAD. We hypothesize that HIV-1 clade B and C Tat proteins might exert differential effects on human primary astrocytes by the upregulation of the IDO gene and protein expression as well as its activity and production of the neurotoxin KYN. RNA extracted from human primary astrocytes treated with either HIV-1 clade B and C Tat proteins was reverse transcribed and analyzed by quantitative real-time PCR to determine IDO gene expression. In addition, the enzymatic activity of IDO and the concentration of KYN were measured in cell lysates and culture supernatants. Our results indicate that HIV-1 clade B Tat protein significantly upregulated the IDO gene and protein expression, IDO enzyme activity, as well as KYN concentration compared to HIV-1 clade C Tat protein. Thus, our studies for the first time demonstrate that HIV-1 clade B Tat protein in human primary astrocytes appears to increase the level of neuropathogenic agents, such as IDO and KYN, as compared to HIV-1 clade C Tat protein. These results provide further evidence that the prevalence of HAD may be correlated with the difference in clades of HIV-1.

Neurobiology of stress-induced reproductive dysfunction in female macaques

It is now well accepted that stress can precipitate mental and physical illness. However, it is becoming clear that given the same stress, some individuals are very vulnerable and will succumb to illness while others are more resilient and cope effectively, rather than becoming ill. This difference between individuals is called stress sensitivity. Stress sensitivity of an individual appears to be influenced by genetically inherited factors, early life (even prenatal) stress, and by the presence or absence of factors that provide protection from stress. In comparison to other stress-related diseases, the concept of sensitivity versus resilience to stress-induced reproductive dysfunction has received relatively little attention. The studies presented herein were undertaken to begin to identify stable characteristics and the neural underpinnings of individuals with sensitivity to stress-induced reproductive dysfunction. Female cynomolgus macaques with normal menstrual cycles either stop ovulating (stress sensitive) or to continue to ovulate (stress resilient) upon exposure to a combined metabolic and psychosocial stress. However, even in the absence of stress, the stress-sensitive animals have lower secretion of the ovarian steroids, estrogen and progesterone, have higher heart rates, have lower serotonin function, have fewer serotonin neurons and lower expression of pivotal serotonin-related genes, have lower expression of 5HT2A and 2C genes in the hypothalamus, have higher gene expression of GAD67 and CRH in the hypothalamus, and have reduced gonadotropin-releasing hormone transport to the anterior pituitary. Altogether, the results suggest that the neurobiology of reproductive circuits in stress-sensitive individuals is compromised. We speculate that with the application of stress, the dysfunction of these neural systems becomes exacerbated and reproductive function ceases.

Effects of long-term hormone treatment and of tibolone on monoamines and monoamine metabolites in the brains of ovariectomised, Cynomologous monkeys

The effects of long-term hormone treatment on monoamines and monoamine metabolites in different regions of the primate brain were examined and compared. Ovariectomised Cynomologous monkeys received daily oral administration of either conjugated equine oestrogens (CEE), CEE + medroxyprogesterone acetate (MPA), or a low or high dose of tibolone, for a period of 2 years. Tissue punches collected from frozen sections through various regions of the forebrain, midbrain, and hindbrain were assayed for levels of dopamine, dihydroxyphenylacetic acid (DOPAC), serotonin, 5-hydroxyindole acetic acid (5-HIAA), and norepinephrine by high-performance liquid chromatography. Few differences between hormone-treated animals and ovariectomised controls were observed. No statistically significant effects of CEE relative to controls were detected in any of the seven brain regions analysed. Animals treated with CEE + MPA showed significant reductions in 5-HIAA in the dorsal raphe nucleus, a significant reduction in dopamine in the hypothalamus, and a significant reduction in serotonin (5-HT) levels in area 8AD of the frontal cortex. Similar to CEE, no significant effects of tibolone relative to controls were detected; however, animals treated with high-dose tibolone showed a decrease in 5-HT levels in the frontal cortex that approached significance and was similar to the effect of CEE + MPA. Collectively, the findings suggest that long-term oral administration of these compounds has relatively few effects on the levels of dopamine, serotonin, and their primary metabolites in the primate brain. This differs from the significant effects on serotonergic and dopaminergic systems detected following parenteral treatment with oestradiol and progesterone, and likely reflects differences between the effects of treating with CEE + MPA versus oestradiol and progesterone on brain monoaminergic systems.

Neuroprotective effects of soy phytoestrogens in the rat brain

Soy extracts are widely used as an alternative to hormone replacement therapy for the treatment of menopausal symptoms. Soy phytoestrogens, such as genistein, may act on the nervous system, affecting mood, cognitive function and behavior. In addition, several studies suggest that soy phytoestrogens are neuroprotective. The hypothesis of the present study was that soy extracts may exert neuroprotection and that this effect is mediated by phytoestrogens such as genistein. To test this hypothesis we assessed whether an acute administration of soy extract or genistein in vivo affects hippocampal neuronal loss induced by the systemic administration of kainic acid to adult Wistar female rats. One week after ovariectomy, animals received one intraperitoneal injection of soy extract (0.2, 1, 2 or 20 mg/kg), one injection of genistein (0.1, 1 or 10 mg/kg) or one injection of vehicle. Thirty minutes later, all animals received one intraperitoneal injection of kainic acid (7 mg/kg) or vehicle. One week after the injections, all animals were fixed by perfusion and the number of Nissl-stained neurons in the hilus of the dentate gyrus was estimated by the optical disector method. Administration of soy extract, even at high doses, did not induce neuronal loss and did not increase neuronal degeneration after kainic acid injury. On the contrary, soy extract at doses ranging from 1 to 20 mg/kg prevented neuronal loss induced by kainic acid. Genistein showed neuroprotective effects only at high dose (10 mg/kg), suggesting that other components in the soy extract are involved in the neuroprotective effect.

Neuroactive steroid effects on cognitive functions with a focus on the serotonin and GABA systems

This article will review neuroactive steroid effects on serotonin and GABA systems, along with the subsequent effects on cognitive functions. Neurosteroids (such as estrogen, progesterone, and allopregnanolone) are synthesized in the central and peripheral nervous system, in addition to other tissues. They are involved in the regulation of mood and memory, in premenstrual syndrome, and mood changes related to hormone replacement therapy, as well as postnatal and major depression, anxiety disorders, and Alzheimer's disease. Estrogen and progesterone have their respective hormone receptors, whereas allopregnanolone acts via the GABA(A) receptor. The action of estrogen and progesterone can be direct genomic, indirect genomic, or non-genomic, also influencing several neurotransmitter systems, such as the serotonin and GABA systems. Estrogen alone, or in combination with antidepressant drugs affecting the serotonin system, has been related to improved mood and well being. In contrast, progesterone can have negative effects on mood and memory. Estrogen alone, or in combination with progesterone, affects the brain serotonin system differently in different parts of the brain, which can at least partly explain the opposite effects on mood of those hormones. Many of the progesterone effects in the brain are mediated by its metabolite allopregnanolone. Allopregnanolone, by changing GABA(A) receptor expression or sensitivity, is involved in premenstrual mood changes; and it also induces cognitive deficits, such as spatial-learning impairment. We have shown that the 3beta-hydroxypregnane steroid UC1011 can inhibit allopregnanolone-induced learning impairment and chloride uptake potentiation in vitro and in vivo. It would be important to find a substance that antagonizes allopregnanolone-induced adverse effects.

A second tryptophan hydroxylase isoform, TPH-2 mRNA, is increased by ovarian steroids in the raphe region of macaques

Recently, a second gene that codes for the rate-limiting enzyme in serotonin synthesis was found in brain, named tryptophan hydroxylase-2 (TPH-2). We sequenced overlapping segments (251 and 510 bp) of 5' monkey TPH-2 and questioned whether TPH-2 is regulated by estrogen (E) and progesterone (P) in serotonin neurons of macaques. Monkey TPH-2 was 97% homologous to human TPH-2 and 65% homologous to monkey TPH-1 in the coding region. Spayed monkeys were administered placebo, E-only, P-only, or E + P for 1 month via Silastic implants (n = 4/treatment) and the midbrain was utilized for TPH-2 in situ hybridization (ISH). Additional monkeys (n = 3/treatment) were used to determine the relative abundance of TPH-2 mRNA with quantitative (q) RT-PCR. In the ISH assay, all of the hormone treatments caused a significant and similar increase in TPH-2 mRNA optical density (fourfold; P < 0.004) and positive pixel area (twofold; P < 0.002) over spayed controls. Treatment with E or E + P for 1 month increased the relative abundance of TPH-2 mRNA over spayed controls in the qRT-PCR assay (ANOVA P < 0.05 and P < 0.007, respectively). In conclusion, ovarian steroids stimulate TPH-2 mRNA expression, which could in turn cause an increase in serotonin synthesis. This would impact many of the neural functions that are governed by serotonin.

Serotonin-related gene expression in female monkeys with individual sensitivity to stress

Female cynomolgus monkeys exhibit different degrees of reproductive dysfunction with moderate metabolic and psychosocial stress. In this study, the expression of four genes pivotal to serotonin neural function was assessed in monkeys previously categorized as highly stress resistant (n=3; normal menstrual cyclicity through two stress cycles), medium stress resistant (n=5; ovulatory in the first stress cycle but anovulatory in the second stress cycle), or low stress resistant (i.e. stress-sensitive; n=4; anovulatory as soon as stress is initiated). In situ hybridization and quantitative image analysis was used to measure mRNAs coding for SERT (serotonin transporter), 5HT1A autoreceptor, MAO-A and MAO-B (monoamine oxidases) at six levels of the dorsal raphe nucleus (DRN). Optical density (OD) and positive pixel area were measured with NIH Image software. In addition, serotonin neurons were immunostained and counted at three levels of the DRN. Finally, each animal was genotyped for the serotonin transporter long polymorphic region (5HTTLPR). Stress sensitive animals had lower expression of SERT mRNA in the caudal region of the DRN (P<0.04). SERT mRNA OD in the caudal DRN was positively correlated with serum progesterone during a pre-stress control cycle (P<0.0007). 5HT1A mRNA OD signal tended to decline in the stress-sensitive group, but statistical difference between averages was lacking in analysis of variance. However, 5HT1A mRNA signal was positively correlated with control cycle progesterone (P<0.009). There was significantly less MAO-A mRNA signal in the stress-sensitive group (P<0.007) and MAO-A OD was positively correlated with progesterone from a pre-stress control cycle (P<0.007). MAO-B mRNA exhibited a similar downward trend in the stress-sensitive group. MAO-B OD also correlated with control cycle progesterone (P<0.003). There were significantly fewer serotonin neurons in the stress-sensitive group. All animals contained only the long form of the 5HTTLPR. Thus, all serotonin-related mRNAs examined in the dorsal raphe to date were lower (SERT, MAO-A) or exhibited a lower trend (5HT1A, MAO-B) in the stress sensitive animals, which probably reflects the lower number of serotonin neurons present.

Estrogen receptor beta in health and disease

Estrogens, acting through its two receptors, ESR1 (hereafter designated ER alpha) and ESR2 (hereafter designated ER beta), have diverse physiological effects in the reproductive system, bone, cardiovascular system, hematopoiesis, and central and peripheral nervous systems. Mice with inactivated ER alpha, ER beta, or both show a number of interesting phenotypes, including incompletely differentiated epithelium in tissues under steroidal control (prostate, ovary, mammary, and salivary glands) and defective ovulation reminiscent of polycystic ovarian syndrome in humans (in ER beta-/- mice), and obesity, insulin resistance, and complete infertility (both in male and female ER alpha-/- mice). Estrogen agonists and antagonists are frequently prescribed drugs with indications that include postmenopausal syndrome (agonists) and breast cancer (antagonists). Because the two estrogen receptors (ERs) have different physiological functions and have ligand binding pockets that differ enough to be selective in their ligand binding, opportunities now exist for development of novel ER subtype-specific selective-ER modulators.

Reflections on the discovery and significance of estrogen receptor beta

We have known for many years that estrogen is more than the female hormone. It is essential in the male gonads, and in both sexes, estrogen has functions in the skeleton and central nervous system, on behavior, and in the cardiovascular and immune systems. An important aspect of the discovery of estrogen receptor (ER) beta is that the diverse functions of estrogen can now be divided into those mediated by ERalpha and those mediated by ERbeta. Pharmacological exploitation of this division of the labors of estrogen is facilitated by the ligand-binding specificity and selective tissue distribution of the two ERs. Because the ligand binding domains of ERalpha and ERbeta are significantly different from each other, selective ligands can be (and have been) developed to target the estrogenic pathway that is malfunctioning, without interfering with the other estrogen-regulated pathways. Because of the absence of ERbeta from the adult pituitary and endometrium, ERbeta agonists can be used to target ERbeta with no risk of adverse effects from chemical castration and uterine cancer. Some of the diseases in which there is hope that ERbeta agonists will be of benefit are prostate cancer, autoimmune diseases, colon cancer, malignancies of the immune system, and neurodegeneration.

Effects of ovarian steroids and raloxifene on proteins that synthesize, transport, and degrade serotonin in the raphe region of macaques

In the monkey dorsal raphe, we reported that 1-month (mo) of estrogen replacement, with or without progesterone supplementation for 14 days, significantly increased tryptophan hydroxylase-1 (TPH-1) mRNA; decreased serotonin reuptake transporter (SERT) mRNA and decreased monoamine oxidase (MAO)-A mRNA, but had no effect on MAO-B mRNA. Here, we questioned what effect would 1 or 5 mo of ovarian hormones or the selective estrogen receptor modulator (SERM), raloxifene, have on TPH protein and phosphorylation, and on protein expression of SERT, MAO-A or MAO-B? Raloxifene antagonizes estrogen in breast or uterus, but estrogen-like activities in the brain have been reported. Cytoplasmic and membrane extracts of the dorsal raphe region were processed for Western blotting. TPH, phosphoserine, SERT, MAO-A, and MAO-B were detected with specific antibodies. The optical densities of the signals were measured with NIH image and analyzed by ANOVA. Both 1 and 5 mo of estrogen, with or without progesterone, and 5 mo of raloxifene significantly increased TPH protein. Administration for 5 mo of estrogen plus progesterone and raloxifene also increased TPH phosphorylation. Estrogen, with or without progesterone, for 1 mo had no effect on SERT protein. However, 5 mo of estrogen and 5 mo of raloxifene increased SERT protein. Estrogen alone or combined with progesterone for 1 mo caused a significant reduction in MAO-A. Yet, after 5 mo of the same treatments, MAO-A was not different from spayed controls. Estrogen alone had no effect on MAO-B. However, the addition of progesterone significantly increased MAO-B. Raloxifene for 5 mo had no effect on MAO-A or MAO-B. Thus, to various extents, estrogen, progesterone, and raloxifene may increase serotonin production and transport. The expression of the degradative enzymes suggests a complex combination of gene transcription, post-transcriptional processing, and substrate feedback mechanisms.

Effects of social status and moderate alcohol consumption on mammary gland and endometrium of surgically postmenopausal monkeys

OBJECTIVE

To evaluate the effects of social subordination stress and chronic moderate alcohol consumption on indices of breast and endometrial cancer risk.

DESIGN

Forty-six adult, ovariectomized, cynomolgus monkeys (Macaca fascicularis) were trained to voluntarily drink a placebo or a two-drink/day equivalent of ethanol (0.5 g/kg), 5 days a week for 26 months, the latter resulting in average blood alcohol levels of 42 mg/100 mL. Indices of cell proliferation and sex steroid receptor abundance were measured.

RESULTS

Compared with dominants, socially subordinate females had increased cell proliferation and proportions of glandular (P < 0.02) and epithelial tissue (P = 0.009) and less stroma (P < 0.02) in endometrium, and increased tissue thickness in breast (P < 0.05). There was no evidence of increased risk of breast or endometrial cancer with chronic moderate alcohol consumption, as indicated by markers of cell proliferation and sex steroid receptor abundance. Chronic moderate alcohol consumption did not effect circulating sex steroid concentrations (all P > 0.10). The adipocyte hormones leptin and adiponectin were correlated with indices of cell proliferation and sex steroid receptor abundance.

CONCLUSIONS

These observations suggest that social status was more important than chronic moderate alcohol consumption in endometrial and breast biology of surgically postmenopausal females. Endogenous sex steroid metabolism was not significantly affected by chronic moderate alcohol exposure consistent with the lack of estrogen-like effects on breast and endometrium. Social subordination stress was associated with initial cellular changes that may increase endometrial cancer risk. Ovariectomized cynomolgus monkeys may be a useful model for the study of effects of social factors and obesity on breast and endometrial cancer risk.

Cognition, mood disorders, and sex hormones

Macaques (Macaca spp.) are useful models to evaluate effects of ovarian sex steroids and selective estrogen receptor modulators (SERMs) on mood and cognitive function due to similarities to women in their reproductive and central nervous systems. The results of nonhuman primate studies support the hypothesis that estrogen mediates specific aspects of attention and memory, yet much work is needed to understand which cognitive processes are affected, whether natural versus surgical menopause effects are different, and the interaction of age and ovarian senescence on cognitive function. This knowledge is necessary to determine whether to support the cognitive function of women in the menopausal phase of life and, if so, to determine efficacious therapeutic interventions. Mood disorders are prevalent in women and are associated with reproductive function in women and macaques. Exogenous steroid therapies, including oral contraceptives and postmenopausal hormone replacement therapies, have behavioral effects in women and appear to affect the behavior and underlying neural substrates of monkeys. Additional research is necessary to confirm and extend these observations. Ovarian steroids have multiple effects on serotonin synthesis, reuptake, and degradation, on neural activity that drives serotonin release, and on receptor activation in primates. This system modulates cognitive function and mood and is the target of a broad class of antidepressant therapies. Understanding the effects of ovarian steroids on the neural serotonergic system is necessary to understand depression in women. These studies are best carried out in primate models, which are more similar to humans in neural serotonergic function than other animal models.

Adrenocortical effects of oral estrogens and soy isoflavones in female monkeys

The goal of this study was to evaluate the long-term adrenocortical effects of premenopausal oral contraceptives (OC) and postmenopausal conjugated equine estrogens (CEE) and soy isoflavones in a female cynomolgus monkey model. Half of the animals received a triphasic OC for a period of 26 months, after which all monkeys were ovariectomized and randomized to one of three diet groups for 36 months: 1). isoflavone-depleted soy protein (control) (n = 54); 2). soy protein with isoflavones (129 mg/d equivalent) (SPI+) (n = 56); or 3). isoflavone-depleted soy protein with CEE (0.625 mg/d equivalent) (n = 59). In the premenopausal phase, OC treatment resulted in significantly higher cortisol (F) and lower dehydroepiandrosterone sulfate, androstenedione, and testosterone relative to intact controls. In the postmenopausal phase, CEE treatment resulted in significantly higher basal F and lower dehydroepiandrosterone sulfate, androstenedione, and testosterone when compared with control and SPI+ diets. Serum F and androgens in the SPI+ group did not differ significantly from the control group. The SPI+ group had significantly lower adrenal weight than either control or CEE groups, and this effect was localized primarily to the zona fasciculata region of the adrenal cortex. These findings suggest that long-term estrogen treatment may contribute to an androgen-deficient and hypercortisolemic state.

Aging, estradiol and time of day differentially affect serotonin transporter binding in the central nervous system of female rats

Estrogen-related changes in serotonergic neuronal transmission, including changes in the number of serotonin transporter (SERT) binding sites, have been cited as a possible cause for changes in mood, memory and sleep that occur during the menopausal transition. However, both aging and estradiol regulate SERT binding sites in the brain. The goal of this experiment was to determine how aging and estrogen interact to regulate SERT levels in the forebrain of young and reproductively senescent female Sprague-Dawley rats using [3H]paroxetine. The density of specific [3H]paroxetine binding in various brain regions was compared in young (2-4 months) and reproductively senescent (10-12 months) female rats at three times of day. In most brain regions examined, estrogen and aging independently increased the number of [3H]paroxetine binding sites. The only region that displayed a reduction in [3H]paroxetine binding with age was the suprachiasmatic nucleus (SCN). Time of day influenced [3H]paroxetine binding in the SCN and the paraventricular thalamus (PVT), two regions known to be involved in the regulation of circadian rhythms. Aging and/or estrogen also altered the pattern of binding in these regions. Thus, based on the results of this study, we conclude that aging and estrogen both act to regulate SERT binding sites in the forebrain of female rats, and that this regulation is region specific.

Estrogen reduces serotonin-1A receptor-mediated oxytocin release and Galpha(i/o/z) proteins in the hypothalamus of ovariectomized rats

The present study examined the effect of estradiol on hypothalamic serotonin-1A (5-HT(1A)) receptor signaling in female rats. We first examined the time-course effects of a single injection of the 5-HT(1A) receptor agonist (+/-)8-OH-DPAT (5, 15 or 30 min prior to decapitation), and dose response of (+)8-OH-DPAT (50, 100, 200 or 500 microg/kg, s.c.) on plasma hormones in ovariectomized rats that received a daily injection of beta-estradiol 3-benzoate (10 microg/day, s.c.) or vehicle (sesame oil) for 2 days. In vehicle- and estrogen-treated rats, the peak response of hormones occurred at 15 min after injection and the time-course of oxytocin and adrenocorticotropic hormone (ACTH) responses to an injection of 8-OH-DPAT were comparable. However, only the oxytocin response was reduced by estrogen treatment. A second experiment compared the ACTH and oxytocin responses with doses of 50 or 200 microg/kg, s.c. of (+)8-OH-DPAT vs. (+/-)8-OH-DPAT in ovariectomized rats that were treated with oil or beta-estradiol 3-benzoate (10 microg/day, s.c.) for 2 days. (+)8-OH-DPAT and (+/-)8-OH-DPAT produced a similar magnitude of increase in plasma levels of ACTH and oxytocin. Treatment with beta-estradiol 3-benzoate produced a significant and comparable reduction in the oxytocin response to the highest dose (200 microg/kg, s.c.) of both (+)8-OH-DPAT and (+/-)8-OH-DPAT but did not alter the ACTH response to either (+)8-OH-DPAT or (+/-)8-OH-DPAT. In the dose-response experiment, a dose of 50 microg/kg of (+)8-OH-DPAT produced a maximal increase in plasma levels of ACTH, while the maximal oxytocin response was achieved with a dose of 200 microg/kg, s.c. Treatment with beta-estradiol 3-benzoate reduced the maximal oxytocin response to (+)8-OH-DPAT (by 29%) but did not alter the ACTH response to any doses of (+)8-OH-DPAT. To examine potential mechanisms mediating the effects of estrogen on 5-HT(1A) receptor signaling, we measured the levels of Galpha(i), Galpha(o) and Galpha(z) proteins, which couple 5-HT(1A) receptors to their effector enzymes, in two subregions of the hypothalamus. The levels of Galpha(z) protein were reduced in the mediobasal hypothalamus (containing the ventromedial and arcuate nuclei), which mainly expresses estrogen receptor-alpha, but not in the paraventricular hypothalamus, which mainly expresses estrogen receptor-beta. Estradiol reduced the levels of Galpha(i2) and Galpha(i3 )proteins in both hypothalamic regions but did not affect Galpha(i1) levels in either area. Combined, the data suggest that racemic and stereoselective 8-OH-DPAT have similar neuroendocrine effects and that both estrogen receptor-alpha and estrogen receptor-beta mediate the reduction in levels of Galpha(i2,3) proteins.