The aim of the research is (1) to study hypothalamic regulation of renin release and (2) to develop a model for central nervous hypertension. The basic preparation is trained beagles with chronically implanted hypothalamic electrodes. We have shown that in more than half the dogs studied stimulation of anterior regions of the hypothalamus elicits sharp reductions in circulating renin activity under a variety of conditions. Studies in this group of dogs are designed to characterize the nature of this phenomenon and to study the role of the hypothalamus in the integrated renin control system. In other dogs, hypothalamic stimulation has resulted in increased renin. We will correlate renin responses with stimulation sites. In addition to studies regarding hypothalamic control of renin, those dogs exhibiting elevation of renin will be chronically stimulated for extended periods and used to develop a model for central nervous hypertension. Our hypothesis for this group is that long-term intermittent stimulation of those hypothalamic structures which activate renin release will lead to augmented angiotensin and increased sensitivity of vascular beds to catecholamines. Repeated stimulation during the period of increased sensitivity will yield greater vascular responses and increments of renin. A positive feed back loop will have been initiated which will lead to hypertension. We will test this hypothesis by renin assay, renal sympathectomy, and adrenalectomy.