The focus of this proposal is to determine the mechanisms by which estrogen and testosterone act to influence peptide containing neurons in the paraventricular nucleus of the hypothalamus (PVN) that are involved in regulating endocrine responses to stress. Females exhibit a more robust adrenocorticotropic hormone (ACTH) and corticosterone (CORT) response to stress when compared to males. This sex difference arises as a result of circulating adult hormone levels. Estrogen augments and testosterone suppresses stress related ACTH and CORT secretion. A novel form of estrogen receptor, termed beta (ER-beta), has been found in magnocellular and parvocellular neurons of the PVN, whereas the classically described alpha form is not present. ER-beta-containing neurons are uniquely distributed and may allow transduction of the estrogen signal to neuropeptide genes. In contrast androgen receptors (AR) are not found in neuroendocrine neurons of the PVN, but are found in neurons in the medial preoptic area (MPOA) and bed nucleus of the stria terminalis (BnST) that project to the PVN. This proposal describes studies to test the hypothesis that estrogen acts directly upon corticotropin releasing hormone (CRH), vasopressin (AVP) or oxytocin (OXY) neurons in the PVN, whereas androgen acts indirectly by modulating GABAergic neurons in the MPOA and BnST that project to the PVN.
5 specific aims are proposed: 1) to determine if the local application of estrogen or testosterone to the PVN alters stress responsive hormone secretion, neuropeptide mRNA, protein content and heteronuclear RNA levels in the PVN. 2) To determine if androgen receptor or estrogen receptor act upon nucleotide sequences in the CRH, AVP or OXY gene promoters. 3) To determine if AR positive, GABA positive neurons in the BnST project to the PVN. 4) To determine if estrogen or androgen modulate glucocorticoid receptor mediated negative feedback regulation of neuropeptide genes in the PVN. 5) To determine if ER-beta or AR interact with glucocorticoid receptor to regulate transcription of reporter genes downstream of the CRH, AVP or OXY gene promoters. Since a dysregulation of stress-responsive hormone secretion is a characteristic of affective disorders, and these are more prevalent in females than males, the long-term goals of this project are to define the role played by estrogen and androgen in the pathology of affective disorders.
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