Recent efforts were directed to understand the cellular and subcellular mechanisms regulating the release of luteinizing hormone-releasing hormone (LHRH) and other hypothalamic peptides that participate in the modulation of pituitary hormone release. Specific studies were conducted to elucidate the role of gabaergic neurotransmitters in the release of LHRH from nerve terminals and the nature of the specific gabaergic receptors involved in the neuronal activation that precedes LHRH release. Additional studies evaluated other events that participate in the peptide-release process, i.e. the involvement of arachidonata metabolites in amplifying or modifying the response to key neurotransmitters, and the additional role played by intracellular messengers such as Ca+2, protein kinase C, and other putative intracellular messengers derived from the metabolism of membrane phospholipids. Other parts of the project were directed to perform an in-depth analysis in vivo of the changes in LHRH prohormone levels and processing in discrete brain nuclei that are known to be involved in regulation of gonadal function. Different experimental paradigms were employed to recreate situations calling for an enhanced (or altered) function of the hypothalamic-pituitary-gonadal axis, such as steroid-feedback manipulations, pregnancy, lactation, estrous cycle, stress, ablation of selected endocrine glands or brain areas, etc. These studies utilized a combination of microdissection, radioimmunoassay, chromatographic and immunocytochemical approaches to better understand the changes in processing of peptide prohormone molecules in different brain regions as well as the release of different prohormone fragments from nerve terminals in vitro.
