Localized injections of 6-hydroxydopamine into lamina terminalis-associated structures: effects on experimentally induced drinking and pressor responses.

Electrolytic lesions of tissues surrounding the anteroventral third ventricle (AV3V) or injections of the chemical neurotoxin, 6-hydroxydopamine (6-OHDA) into the lateral cerebral ventricles result in virtually identical deficits in response to a variety of dipsogenic and pressor challenges. These observations have led to the hypothesis that the integrity of catecholamine (CA) projections into the AV3V region is a prerequisite for elicitation of these thirst and blood pressure responses. This hypothesis was tested in 6-OHDA-injected rats following protocols designed to deplete CA's in discrete structures associated with the lamina terminalis. Post-injection response deficits, coupled with histofluorescent assessments of CA depletions in specific anterior forebrain nuclei, support the stated hypothesis. In addition, the findings indicate that thirst deficits to systemic as well as central dipsogenic challenges are both selective and dissociable and that 6-OHDA lesions of any of the more ventrally situated target nuclei result in significantly attenuated blood pressure responses to centrally injected angiotensin II.