Neonatal stimulation of 5-HT2receptors reduces androgen receptor expression in the rat anteroventral periventricular nucleus and sexually dimorphic preoptic area

Review of electrochemical and optical biosensors for testosterone measurement

Testosterone is an anabolic steroid and a major sex hormone in males. It plays vital roles, including developing the testis, penis, and prostate, increasing muscle and bone, and sperm production. In both men and women, testosterone levels should be in normal ranges. Besides, testosterone and its analogs are major global contributors to doping in sport. Due to the importance of testosterone testing, novel, accurate biosensors have been developed. This review summarizes the various methods for testosterone measurement. Also, recent optical and electrochemical approaches for the detection of testosterone and its analogs have been discussed.

Paroxetine effects in adult male rat colon: Focus on gut steroidogenesis and microbiota

Paroxetine, a selective serotonin reuptake inhibitor (SSRI), is prescribed to treat psychiatric disorders, although an off-label SSRI use is also for functional gastrointestinal disorders. The mutual correlation between serotonin and peripheral sex steroids has been reported, however little attention to sex steroids synthesized by gut, has been given so far. Indeed, whether SSRIs, may also influence the gut steroid production, immediately after treatment and/or after suspension, is still unclear. The finding that gut possesses steroidogenic capability is of particular relevance, also for the existence of the gut-microbiota-brain axis, where gut microbiota represents a key orchestrator. On this basis, adult male rats were treated daily for two weeks with paroxetine or vehicle and, 24 h after treatment and at 1 month of withdrawal, steroid environment and gut microbiota were evaluated. Results obtained reveal that paroxetine significantly affects steroid levels, only in the colon but not in plasma. In particular, steroid modifications observed immediately after treatment are not overlap with those detected at withdrawal. Additionally, paroxetine treatment and its withdrawal impact gut microbiota populations differently. Altogether, these results suggest a biphasic effect of the drug treatment in the gut both on steroidogenesis and microbiota.

Serotonin Pretreatment Abolishes Sex-specific NMDA-induced Seizure Behavior in Developing Rats

Neuronal excitability and susceptibility to excitotoxic damage can be sex-specific, with neurons from males usually being more 'easily excitable' compared to neurons from females, especially during development. Increased excitability at an individual neuronal level can lead to the formation of hyperexcitable neuronal networks, which, consequently can make the brain more seizure prone. Both animal and clinical data suggest that males experience more frequent and severe seizures than do females. Serotonin (5-hydroxytryptamine; 5-HT) can mediate neuronal excitability and seizure behavior, often serving as an anticonvulsant. Importantly, 5-HT signaling during parts of the perinatal period is sexually dimorphic. Sex differences during development have been reported in both serotonin levels and receptor type (excitatory vs. inhibitory) expression in a manner that may leave the male brain more vulnerable to over-excitation. Thus, we aimed to determine if the anticonvulsant effects of 5-HT were sex- and/or age-dependent in juvenile animals. We report a baseline sex difference in N-methyl-d-aspartate (NMDA)-induced seizure behavior and hippocampal neuronal loss, with postnatal day (PND) 14 males exhibiting more severe seizure behavior compared to females. Pretreatment with the general 5-HT receptor agonist 5-methoxytryptamine (5-MT) abolishes baseline sex differences, providing an anticonvulsant effect for males only. These sex differences appear to be at least in part organized by testosterone, as females given neonatal androgen exhibit a seizure behavior profile in between that of males and females.

Serotonin regulates prostate growth through androgen receptor modulation

Aging and testosterone almost inexorably cause benign prostatic hyperplasia (BPH) in Human males. However, etiology of BPH is largely unknown. Serotonin (5-HT) is produced by neuroendocrine prostatic cells and presents in high concentration in normal prostatic transition zone, but its function in prostate physiology is unknown. Previous evidence demonstrated that neuroendocrine cells and 5-HT are decreased in BPH compared to normal prostate. Here, we show that 5-HT is a strong negative regulator of prostate growth. In vitro, 5-HT inhibits rat prostate branching through down-regulation of androgen receptor (AR). This 5-HT’s inhibitory mechanism is also present in human cells of normal prostate and BPH, namely in cell lines expressing AR when treated with testosterone. In both models, 5-HT’s inhibitory mechanism was replicated by specific agonists of 5-Htr1a and 5-Htr1b. Since peripheral 5-HT production is specifically regulated by tryptophan hydroxylase 1(Tph1), we showed that Tph1 knockout mice present higher prostate mass and up-regulation of AR when compared to wild-type, whereas 5-HT treatment restored the prostate weight and AR levels. As 5-HT is decreased in BPH, we present here evidence that links 5-HT depletion to BPH etiology through modulation of AR. Serotoninergic prostate pathway should be explored as a new therapeutic target for BPH.

Pre- and postnatal bisphenol A treatment does not alter the number of tyrosine hydroxylase-positive cells in the anteroventral periventricular nucleus (AVPV) of weanling male and female rats

Exposure to Bisphenol A (BPA) may interfere with brain sexual differentiation. Altered numbers of tyrosine hydroxylase (TH) cells in the rodent anteroventral periventricular nucleus (AVPV) after developmental BPA treatment have been reported; however, definitive conclusions are lacking. The current study incorporated many of the guidelines suggested for endocrine disrupter research. Specifically, ethinyl estradiol (EE2) served as a reference estrogen, exogenous environmental estrogen exposure was controlled, BPA was administered orally, and subjects consumed a low phytoestrogen diet. Here, on gestational days 6-21, Sprague-Dawley rats (10-15/group) were gavaged with 2.5 or 25.0 µg BPA/kg/day or 5.0 or 10.0 µg EE2/kg/day or the vehicle (5 ml of 0.3% aqueous carboxymethylcellulose/kg/day). A naïve control group was weighed and restrained, but not gavaged. Beginning on postnatal day (PND) 1 and continuing until PND 21, the 4 pups/sex/litter were orally treated with the same dose their dam had received. On PND 21, 1/sex/litter was perfused and the brain removed. TH immunoreactivity (TH-ir) was counted in 8 images/pup by a technician blind to treatment status. ANOVA results indicated significantly higher TH-ir cells/mm(2) in females (main effect of sex: p<0.01); however, there was no significant effect of treatment or a significant interaction of treatment with sex. In a separate untreated group of PND 21 Sprague-Dawley pups, AVPV volume was quantified and no significant sexual dimorphism was apparent. Similar to our reported results of behavioral assessments, the BPA treatment paradigm used here (2.5 or 25.0 µg BPA/kg/day administered orally) does not appear to cause significant alterations in AVPV TH-ir.

Species differences in androgen receptor expression in the medial preoptic and anterior hypothalamic areas of adult male and female rodents

The medial preoptic and anterior hypothalamic areas (MPO/AH) are important androgen targets regulating homeostasis, neuroendocrinology and circadian rhythm as well as instinctive and sociosexual behaviors. Although species differences between rats and mice have been pointed out in terms of morphology and physiology, detailed distributions of androgen receptor (AR) have never been compared between the two rodents. In the present study, AR distribution was examined immunohistochemically in serial sections of the MPO/AH and compared for adult rats and mice. Western blotting and immunohistochemistry clearly demonstrated that AR expression in the brain was stronger in mice than in rats and was stronger in males than in females. In addition, we found (1) an "obliquely elongated calbindin-ir cell island" in mice medial preoptic nucleus (MPN) expressed AR intensely, as well as the sexually dimorphic nucleus in the MPN (SDN-MPN) in rats, strongly supporting a "putative SDN-MPN" previously proposed in mice; (2) AR expression in the suprachiasmatic nucleus (SCN) was much more prominent in mice than in rats and differed in localization between the two species; (3) a mouse-specific AR-ir cell cluster was newly identified as the "tear drop nucleus (TDN)", with male-dominant sexual dimorphism; and (4) two rat-specific AR-ir cell clusters were also newly identified as the "rostral and caudal nebular islands", with male-dominant sexual dimorphism. The present results may provide basic morphological evidence underlying species differences in androgen-modified psychological, physiological and endocrinergic responses. Above all, the findings of the mouse-specific TDN and differing AR expression in the SCN might explain not only species difference in gonadal modification of circadian rhythm, but also distinct structural bases in the context of transduction of SCN oscillation. The current study could also serve as a caution that data on androgen-sensitive functions obtained from one species should not always be directly applied to others among rodents.

Effects of developmental hyperserotonemia on juvenile play behavior, oxytocin and serotonin receptor expression in the hypothalamus are age and sex dependent

There is a striking sex difference in the diagnosis of Autism Spectrum Disorder (ASD), such that males are diagnosed more often than females, usually in early childhood. Given that recent research has implicated elevated blood serotonin (hyperserotonemia) in perinatal development as a potential factor in the pathogenesis of ASD, we sought to evaluate the effects of developmental hyperserotonemia on social behavior and relevant brain morphology in juvenile males and females. Administration of 5-methoxytryptamine (5-MT) both pre- and postnatally was found to disrupt normal social play behavior in juveniles. In addition, alterations in the number of oxytocinergic cells in the lateral and medial paraventricular nucleus (PVN) were evident on postnatal day 18 (PND18) in 5-MT treated females, but not treated males. 5-MT treatment also changed the relative expression of 5-HT(1A) and 5-HT(2A) receptors in the PVN, in males at PND10 and in females at PND18. These data suggest that serotonin plays an organizing role in the development of the PVN in a sexually dimorphic fashion, and that elevated serotonin levels during perinatal development may disrupt normal organization, leading to neurochemical and behavioral changes. Importantly, these data also suggest that the inclusion of both juvenile males and females in studies will be necessary to fully understand the role of serotonin in development, especially in relation to ASD.

Developmental fluoxetine exposure and prenatal stress alter sexual differentiation of the brain and reproductive behavior in male rat offspring

Depression during pregnancy and postpartum is a significant health problem and affects up to 20% of women. While selective serotonin reuptake inhibitor (SSRI) medications are the drug of choice for treatment of maternal depression, the combined effect of maternal depression and perinatal SSRI exposure on offspring development is poorly investigated. Our aim was to determine the role of exposure to fluoxetine during development on sexual behavior and sexually dimorphic brain structures in male offspring using a rodent model of maternal adversity. Sprague-Dawley rat dams were stressed during gestation and were chronically treated throughout lactation with either fluoxetine or vehicle beginning on postnatal day 1. Four groups of offspring were used: (1) Control+Vehicle, (2) Control+Fluoxetine, (3) Prenatal Stress+Vehicle, and (4) Prenatal Stress+Fluoxetine. We show here that developmental fluoxetine treatment decreases the anogenital distance in juvenile male offspring. In adult male offspring, maternal fluoxetine treatment results in a decrease in the number of intromissions, a longer latency to the first intromission, and a longer latency to the first ejaculation. Furthermore, developmental fluoxetine and/or prenatal stress decrease the area of the sexually dimorphic nucleus of the preoptic area (SDN-POA). Prenatal stress, but not exposure to developmental fluoxetine, decreases the number of tyrosine hydroxylase (TH)-positive cells in anteroventral periventricular nucleus (AVPv) and the volume of the posterior bed nucleus of the stria terminalis (pBST) in male offspring. These results provide important evidence for the long-term impact of maternal adversity and maternal fluoxetine use on the development of primary endocrinology systems in juvenile and adult male offspring.

Cerebral serotonin transporter asymmetry in females, males and male-to-female transsexuals measured by PET in vivo

The serotonergic system modulates brain functions that are considered to underlie affective states, emotion and cognition. Several lines of evidence point towards a strong lateralization of these mental processes, which indicates similar asymmetries in associated neurotransmitter systems. Here, our aim was to investigate a potential asymmetry of the serotonin transporter distribution using positron emission tomography and the radioligand [(11)C]DASB in vivo. As brain asymmetries may differ between sexes, we further aimed to compare serotonin transporter asymmetry between females, males and male-to-female (MtF) transsexuals whose brains are considered to be partly feminized. Voxel-wise analysis of serotonin transporter binding in all groups showed both strong left and rightward asymmetries in several cortical and subcortical structures including temporal and frontal cortices, anterior cingulate, hippocampus, caudate and thalamus. Further, male controls showed a rightward asymmetry in the midcingulate cortex, which was absent in females and MtF transsexuals. The present data support the notion of a lateralized serotonergic system, which is in line with previous findings of asymmetric serotonin-1A receptor distributions, extracellular serotonin concentrations, serotonin turnover and uptake. The absence of serotonin transporter asymmetry in the midcingulate in MtF transsexuals may be attributed to an absence of brain masculinization in this region.

The Buzz about anabolic androgenic steroids: electrophysiological effects in excitable tissues

Anabolic androgenic steroids (AAS) comprise a large and growing class of synthetic androgens used clinically to promote tissue-building in individuals suffering from genetic disorders, injuries, and diseases. Despite these beneficial therapeutic applications, the predominant use of AAS is illicit: these steroids are self-administered to promote athletic performance and body image. Hand in hand with the desired anabolic actions of the AAS are untoward effects on the brain and behavior. While the signaling routes by which the AAS impose both beneficial and harmful actions may be quite diverse, key endpoints are likely to include ligand-gated and voltage-dependent ion channels that govern the activity of electrically excitable tissues. Here, we review the known effects of AAS on molecular targets that play critical roles in controlling electrical activity, with a specific focus on the effects of AAS on neurotransmission mediated by GABA(A) receptors in the central nervous system.

Chronic exposure to anabolic androgenic steroids alters activity and synaptic function in neuroendocrine control regions of the female mouse

Disruption of reproductive function is a hallmark of abuse of anabolic androgenic steroids (AAS) in female subjects. To understand the central actions of AAS, patch clamp recordings were made in estrous, diestrous and AAS-treated mice from gonadotropin releasing hormone (GnRH) neurons, neurons in the medial preoptic area (mPOA) and neurons in the anteroventroperiventricular nucleus (AVPV); regions known to provide GABAergic and kisspeptin inputs to the GnRH cells. Action potential (AP) frequency was significantly higher in GnRH neurons of estrous mice than in AAS-treated or diestrous animals. No significant differences in AAS-treated, estrous or diestrous mice were evident in the amplitude or kinetics of spontaneous postsynaptic currents (sPSCs), miniature PSCs or tonic currents mediated by GABA(A) receptors or in GABA(A) receptor subunit expression in GnRH neurons. In contrast, the frequency of GABA(A) receptor-mediated sPSCs in GnRH neurons showed an inverse correlation with AP frequency across the three hormonal states. Surprisingly, AP activity in the medial preoptic area (mPOA), a likely source of GABAergic afferents to GnRH cells, did not vary in concert with the sPSCs in the GnRH neurons. Furthermore, pharmacological blockade of GABA(A) receptors did not alter the pattern in which there was lower AP frequency in GnRH neurons of AAS-treated and diestrous versus estrous mice. These data suggest that AAS do not impose their effects either directly on GnRH neurons or on putative GABAergic afferents in the mPOA. AP activity recorded from neurons in kisspeptin-rich regions of the AVPV and the expression of kisspeptin mRNA and peptide did vary coordinately with AP activity in GnRH neurons. Our data demonstrate that AAS treatment imposes a "diestrous-like" pattern of activity in GnRH neurons and suggest that this effect may arise from suppression of presynaptic kisspeptin-mediated excitatory drive arising from the AVPV. The actions of AAS on neuroendocrine regulatory circuits may contribute the disruption of reproductive function observed in steroid abuse.

The anti-dopaminergic agent, haloperidol, antagonises the feminising effect of neonatal serotonin on sexually dimorphic hypothalamic nuclei and tyrosine hydroxylase immunoreactive neurones

There is a transient fall in hypothalamic serotonin (5-hydroxytryptamine; 5-HT) activity in the second week post partum in male but not female rats. When this fall is masked by administration of the 5-HT(2) agonist (-) 2,5-dimethoxy-4-iodophenyl]-2-aminopropane hydrochloride [(-)DOI], over days 8-16 post partum, males are feminised in adulthood. To investigate whether the effect of 5-HT is mediated by dopamine and whether testosterone exerts its masculinising effect by reducing 5-HT and dopamine activity, male pups were treated with (-)DOI alone or together with the dopamine antagonist, haloperidol, over days 8-16 post partum, whereas females were treated with testosterone propionate on day 2 post partum. In adulthood, the volumes of the anteroventral periventricular nucleus (AVPV), sexually dimorphic nucleus of the preoptic area (SDN-POA) and arcuate nucleus (ARC) were determined, together with the number of tyrosine hydroxylase-immunoreactive (TH-ir) cells and fibres within them. The concentrations of 5-HT, dopamine and their metabolites were also measured. (-)DOI treatment increased the volume of the AVPV, decreased that of the SDN-POA and increased the number of TH-ir cells in the AVPV. These feminising effects were antagonised by concurrent haloperidol treatment. Neonatal testosterone propionate masculinised the volumes of the female AVPV and SDN-POA and reduced the number of TH-ir cells in the AVPV. Dopamine and 5-HT turnover in the AVPV was greater in female compared to male rats and neonatal testosterone propionate reduced dopamine concentration in the female AVPV. Neonatal (-)DOI had no effect on dopamine and 5-HT activity in the AVPV but increased both in the ARC. The findings that TH-ir neurone number and dopamine activity are greater in the female AVPV; the feminising effect of 5-HT is prevented by a haloperidol; and the masculinising effect of testosterone propionate is accompanied by a decrease in TH-ir neurone number and dopamine concentration in the female AVPV, suggest that dopamine is involved in hypothalamic sexual differentiation and may mediate the effect of 5-HT.