The complexity of gonadal steroid hormone actions is reflected in their broad and diverse effects on a host of integrated systems including reproductive physiology, sexual behavior, stress responses, immune function, cognition, and neural protection. Understanding the specific contributions of androgens and estrogens in neurons that mediate these important biological processes is central to the study of neuroendocrinology. Of particular interest in recent years has been the biological role of androgen metabolites. The goal of this review is to highlight recent data delineating the specific brain targets for the dihydrotestosterone metabolite, 5α-androstane, 3β, 17β-diol (3β-Diol). Studies using both in vitro and in vivo approaches provide compelling evidence that 3β-Diol is an important modulator of the stress response mediated by the hypothalmo-pituitary-adrenal axis. Further, the actions of 3β-Diol are mediated by estrogen receptors, and not androgen receptors, often through a canonical estrogen response element in the promoter of a given target gene. These novel findings compel us to re-evaluate the interpretation of past studies and the design of future experiments aimed at elucidating the specific effects of androgen receptor signaling pathways.

5α-Androstane-3β, 17β-diol (3βAdiol) is a metabolite of the potent androgen, 5α-dihydrotestosterone. Recent studies showed that 3βAdiol binds to estrogen receptor (ER)-β and regulates growth of the prostate gland through an estrogen, and not androgen, receptor-mediated pathway. These data raise the possibility that 3βAdiol could regulate important physiological processes in other tissues that produce 3βAdiol, such as the brain. Although it is widely accepted that the brain is a target for 5α-dihydrotestosterone action, there is no evidence that 3βAdiol has a direct action in neurons. To explore the molecular mechanisms by which 3βAdiol might act to modulate gene transcription in neuronal cells, we examined whether 3βAdiol activates ER-mediated promoter activity and whether ER transactivation is facilitated by a classical estrogen response element (ERE) or an AP-1 complex. The HT-22 neuronal cell line was cotransfected with an expression vector containing ERα, ER-β1, or the ERβ splice variant, ER-β2 and one of two luciferase-reporter constructs containing either a consensus ERE or an AP-1 enhancer site. Cells were treated with 100 nm 17β-estradiol, 100 nm 3βAdiol, or vehicle for 15 h. We show that 3βAdiol activated ER-β1-induced transcription mediated by an ERE equivalent to that of 17β-estradiol. By contrast, 3βAdiol had no effect on ERα- or ER-β2-mediated promoter activity. Moreover, ER-β1 stimulated transcription mediated by an ERE and inhibited transcription by an AP-1 site in the absence of ligand binding. These data provide evidence for activation of ER signaling pathways by an androgen metabolite in neuronal cells.

Increasing evidence suggests that fibroblast growth factors (FGFs) are neurotrophic in GnRH neurons. However, the extent to which FGFs are involved in establishing a functional GnRH system in the whole organism has not been investigated. In this study, transgenic mice with the expression of a dominant-negative FGF receptor mutant (FGFRm) targeted to GnRH neurons were generated to examine the consequence of disrupted FGF signaling on the formation of the GnRH system. To first test the effectiveness of this strategy, GT1 cells, a GnRH neuronal cell line, were stably transfected with FGFRm. The transfected cells showed attenuated neurite outgrowth, diminished FGF-2 responsiveness in a cell survival assay, and blunted activation of the signaling pathway in response to FGF-2. Transgenic mice expressing FGFRm in a GnRH neuron-specific manner exhibited a 30% reduction in GnRH neuron number, but the anatomical distribution of GnRH neurons was unaltered. Although these mice were initially fertile, they displayed several reproductive defects, including delayed puberty, reduced litter size, and early reproductive senescence. Overall, our results are the first to show, at the level of the organism, that FGFs are one of the important components involved in the formation and maintenance of the GnRH system.

Przybycien-Szymanska MM, Rao YS, Pak TR. Binge-pattern alcohol exposure during puberty induces sexually dimorphic changes in genes regulating the HPA axis. Am J Physiol Endocrinol Metab 298: E320 -E328, 2010. First published December 1, 2009; doi:10.1152/ajpendo.00615.2009.-Maternal alcohol consumption during critical periods of fetal brain development leads to devastating long-term consequences on adult reproductive physiology, cognitive function, and social behaviors. However, very little is known about the long-term consequences of alcohol consumption during puberty, which is perhaps an equally dynamic and critical period of brain development. Alcohol abuse during adulthood has been linked with an increase in clinically diagnosed anxiety disorders, yet the etiology and neurochemical mechanisms of alcohol-induced anxiety behavior is unknown. In this study, we determined the effects of binge ethanol exposure during puberty on two critical central regulators of stress and anxiety behavior: corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP). Our results showed that ethanol increased plasma corticosterone (CORT) levels in both sexes, yet binge-treated animals had significantly lower CORT levels than animals exposed to a single dose, suggesting that the hypothalamo-pituitary-adrenal (HPA) axis habituated to the repeated stressful stimuli of ethanol. Binge ethanol exposure also significantly increased CRH and AVP gene expression in the paraventricular nucleus of males, but not females. Overall, our results demonstrate that binge ethanol exposure during puberty changes the central expression of stress-related genes in a sex-specific manner, potentially leading to permanent dysregulation of the HPA axis and long-term behavioral consequences.hypothalamus; puberty; arginine vasopressin; corticotrophin-releasing hormone; corticosterone; hypothalamo-pituitary-adrenal axis ALCOHOL ABUSE DURING ADOLESCENCE is a growing fundamental heath concern in the United States. According to the US Department of Health and Human Services, boys on average have had their first drink before age 11, and girls before age 13, with the overall statistics showing that 41% of teenagers have had their first drink by age 14. Underage drinkers typically adopt a "binge" pattern of alcohol consumption, defined by the National Institute on Alcohol Abuse and Alcoholism as heavy, episodic drinking in which enough alcohol is consumed in one sitting to bring the blood alcohol concentration (BAC) Ͼ0.08 g/100 g (55). During adolescence, significant neural remodeling occurs as evidenced by changes in cortical gray matter (22,29,37), neurogenesis (40), and increased synaptic connectivity (14,49,57), raising the possibility that alcohol consumption during this critical period can lead to long-term neurobiological and behavioral defects.One neurological system that undergoes extensive plasticity during pubertal development is the hypothalamo-pituitaryadrenal (HPA) axis (46). Under normal physiological conditions, an acute psychological or ph...