The overall objective of the proposed study is to determine the underlying hypothalamic mechanisms that are responsible for signaling the releasing factor "producing cells" to initiate secretion of hormone from the adenohypophysis. An interdisciplinary approach utilizing intracellular staining with Procion yellow dye, immunofluorescence with LRF antibody, antidromic identification, and microelectrophoretic techniques will be used to study the integrative mechanisms existing between the central nervous and endocrine systems. Experiments will be conducted on LRF-containing cells to determine (1) the precise localization of their cell bodies and terminal endings, (2) their detailed morphology and relation to neuronal integration, (3) their electrical characteristics and neurosecretory properties, (4) their pharmacological sensitivity to the monoamines, (5) the possible correlation between electrically- and chemically-induced changes in their electrical activity with hormonal release, and (6) possible feedback loops on these neurons, by studying their sensitivity to iontophoretically applied ovarian hormones, gonadotropins and releasing factors.