EVIDENCE NITRIC-OXIDE MEDIATES THE VASODEPRESSOR RESPONSE TO HYPOXIA IN SINO-DENERVATED RATS

Systemic hypoxia, produced in deeply anesthetized, paralyzed rats in which arterial chemoreceptors were denervated, elicited a decrease in arterial pressure (AP) averaging -47 mmHg. Systemic administration of N(G)-nitro-L-arginine (L-NO2Arg), an inhibitor of nitric oxide (NO) synthase, attenuated the hypoxic depressor response by 79% and elevated AP by 21 mmHg. The effects of L-NO2Arg on the hypoxic depressor response and arterial pressure were reversed by systemic administration of L- but not D-arginine. Elevation of AP with arginine-vasopressin or reduction of AP with nitroprusside to the pre-L-NO2Arg levels did not modify the fall of AP to hypoxia. Endogenous NO synthesized in vivo from L-arginine, mediates most of the hypoxic depressor response.