Study on the involvement of the L-arginine/nitric oxide pathway in the central cardiovascular regulation in the chloralose-anaesthetized cat.

The role of the L-arginine/nitric oxide pathway in mediating the central control of blood pressure and heart rate, has been investigated in chloralose-anaesthetized cats. L-arginine (10 micrograms to 10 mg), administered intracerebroventricularly into a lateral ventricle, produced a dose-dependent rise in mean blood pressure (7 to 28%) and heart rate (4 to 34%). D-arginine (1 mg), on the other hand, did not produce any change. The effect of L-arginine (100 micrograms) was dose-dependently inhibited by pretreatment with either L-NAME (1 mg) or methylene blue (400 micrograms). Sodium nitroprusside (1 microgram to 10 micrograms, 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 methylene 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.