Role of the anterior region of the third ventricle in the cardiovascular responses produced by systemic injection of a nitric oxide synthase inhibitor

This study examined whether a prior electrolytic lesion of the tissue surro unding the anteroventral third ventricle (AV3V) would affect the increase i n mean arterial blood pressure (MAP) and the fall in heart rate (HR) produc ed by systemic injection of the nitric oxide synthesis (NOS) inhibitor, N-G -nitro-L-arginine methyl eater (L-NAME; 25 mu mol/kg, i.v.) in conscious ra ts. L-NAME produced a smaller increase in MAP in AV3V-lesion than in sham-l esion rats (+ 19 +/- 3 vs. + 40 +/- 3 mmHg, respectively; P < 0.05), In con trast, L-NAME produced similar falls in HR in the AV3V-lesion and sham-lesi on rats (-103 +/- 15 vs. -97 +/- 8 bpm, respectively; P < 0.05). These find ings demonstrate that the L-NAME-induced presser response is dependent upon the integrity of the AV3V region, whereas the L-NAME-induced bradycardia i s not. (C) 1999 Elsevier Science B.V. All rights reserved.