The objective of this project is to gain an increased understanding of the neuronal circuitry within the tuberal hypothalamus involved in the control of anterior pituitary function. Electrophysiological methods will be utilized to record from neurons in tissue cultures of the medial basal hypothalamus (MBH) of neonatal rats as well as from freshly prepared slices of adult rat hypothalamus. Neuroactive substances are applied locally from micropipettes or in known concentrations by perfusion. These methods will allow us to define the types of neuronal interactions and putative neurotransmitters intrinsic to this region, as well as understand the responses of the neurons and circuits in this region to hormones and other putative neurotransmitters involved in endocrine regulation. We will determine if the peptide hormones and putative neurotransmitters which affect MBH neuronal activity do so through specific receptors. Additionally, we will utilize intracellular recording from cultured MBH neurons to determine hormone- and neurotransmitter-elicited changes in membrane potential and conductance and the ionic species involved. Effects of chronic steroid treatment of cultures on neuronal activity and responses to neurotransmitters and hormones will be assessed. It is intended that these experiments provide critical information in the areas of information processing by discrete brain regions and neurotransmitter effects on endocrine processes.