The ultimate goal of this research is to contribute to our understanding of the neuronal machinery that is responsible for vasopressin release by the hypothalamic magnocellular neuroendocrine cells. We propose to study the response characteristics of the whole neuronal population by measuring plasma arginie vasopressin (AVP) in the unanesthetized monkey and anesthetized cat. Stimuli for release of AVP will include osmometric, volumetric, chemical and neural. These will be applied via intravascular, intraventricular and intracerebral routes. In the unanesthetized monkey we shall study plasma AVP simultaneous to study of antidromically identified single supraoptic and paraventricular neurons in response to various natural states. A chronic monkey epileptic model will be developed with amygdala kindling, amygdala alumina focus and generalized seizures. Using these pathophysiological stimuli, plasma AVP and single magnocellular neuroendocrine cells will be studied. We expect that these studies will further define the electrophysiological characteristics of hypothalamic vasopressinergic neuroendocrine cells & their role in the homeostasis of body fluids in the normal and epileptic monkey.