STUDY ON THE INVOLVEMENT OF THE L-ARGININE NITRIC-OXIDE PATHWAY IN THE CENTRAL CARDIOVASCULAR REGULATION IN THE CHLORALOSE-ANESTHETIZED CAT

The role of the L-arginine/nitric oxide pathway in mediating the centr al control of blood pressure and heart rate, has been investigated in chloralose-anaesthetized cats. L-arginine (10 mu g to 10mg), administe red intracerebroventricularly into a lateral ventricle, produced a dos e-dependent rise in mean blood pressure (7 to 28%) and heart rate (4 t o 34%). D-arginine (1 mg), on the other hand, did not produce any chan ge. The effect of L-arginine (100 mu g) was dose-dependently inhibited by pretreatment with either L-NAME (1 mg) or methylene blue (400 mu g ). Sodium nitroprusside (1 mu g to 10 mu g, intracerebroventricularly) , a spontaneous source of nitric oxide, produced a dose-dependent fall in mean blood pressure (6 to 19%) with a moderate rise in heart rate (3 to 10%). The effect of nitroprusside was markedly inhibited by meth ylene blue, but not by L-NAME. The results suggest that the L-arginine /nitric oxide pathway in the central nervous system is involved in the blood pressure regulation in the cat.