Vasomotor projections from the anteroventral third ventricle (AV3V) region

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Abstract
The anteroventral 3rd ventricle (AV3V) region is necessary for the development of a variety of models of experimental hypertension. Neuroanatomic studies have identified descending projections from this region to the mesencephalic central gray and tegmentum. This study was done to identify functionally the projections involved in cardiovascular regulation from the AV3V region to the mesencephalon. Regional hemodynamic responses to electrical stimulation of the AV3V region were compared with responses to stimulation of the rostral central gray, and these responses were compared before and after ablation of mesencephalic tissue. Stimulation of the AV3V region elicited hindquarter vasodilation and renal and mesenteric vasoconstriction associated with a depressor response and bradycarida. These responses were partially dependent on adrenal catecholamines since adrenalectomy reduced hindquarter, mesenteric and depressor responses. Regional hemodynamic responses to central gray stimulation were qualitatively similar and also demonstrated a partial dependence on adrenal catecholamines. After electrolyte ablation of central gray tissue, significant reductions in hindquarter, mesenteric and depressor responses to AV3V stimulation were observed. A cardiovascular control system important for the development of several models of hypertension may be dependent on neuronal projections from the rostral medial hypothalamus through the mesencephalic central gray.