Periventricular forebrain mechanisms for blood pressure regulation.

Periventricular forebrain regions participate in body fluid and cardiovascular regulatory mechanisms that are intimately related to neural participation in experimental hypertension. Ablation of preoptic-hypothalamic periventricular tissue surrounding the anteroventral third ventricle (AV3V) disrupts both angiotensin (AngII) and sodium regulatory mechanisms and prevents experimental hypertension in either renin-dependent or -independent models. When AV3V is spared, and central AngII pressor mechanisms are interrupted by subfornical organ ablation or anterior hypothalamic knife cuts, renin-dependent but not renin-independent models of hypertension are prevented. Volume-expanded models of hypertension may be mediated by a natriuretic hormone that also inhibits the sodium-potassium pump in vascular smooth muscle, resulting in increased vasoconstriction. Volume expansion-induced release of this humoral ATPase inhibitor is attenuated in rats with AV3V lesions. In the renin-independent, reduced renal mass model, development of hypertension is correlated with increased plasma levels of sodium-potassium pump inhibitor. AV3V ablation blocks both the hypertension and the increase in humoral ATPase inhibitor. Thus, Thus, central angiotensin pressor and natriuretic mechanisms overlap in AV3V, and prevention of renin-dependent and volume-dependent models of experimental hypertension by AV3V ablation appears linked to disruption of these functionally separable systems.