Central administration of a nitric oxide synthase inhibitor causes pressor responses via the sympathetic nervous system and the renin- angiotensin system in Wistar rats

The central roles of nitric oxide (NO) in regulations of the blood pressure and heart rate were examined in anesthetized rats. Intracerebroventricular (i.c.v.) injection of N(ω)-nitro-L-arginine methyl ester (L-NAME) caused dose-dependent increase in the blood pressure and heart rate. The pressor response of the blood pressure to L-NAME (2 μmol, i.c.v.) was reduced by L-arginine (5 μmol, i.c.v). Pretreatment with a ganglionic blocker, pentolinium (10 mg/kg, i.v.), significantly inhibited both pressor responses induced by L-NAME (2 μmol, i.c.v). The later pressor response of the blood pressure to L-NAME was also inhibited by the angiotensin II AT-1 blocker losartan (10 mg/kg, i.v). These results suggest that the response of the blood pressure to L-NAME is mediated by both the sympathetic nervous system and the renin-angiotensin system.