HYPOTHALAMIC BLOOD-FLOW REMAINS UNALTERED FOLLOWING CHRONIC NITRIC-OXIDE SYNTHASE BLOCKADE IN RATS

The effect of the chronic oral application of N-G-nitro-L-arginine met hyl eater (L-NAME), a potent inhibitor of nitric oxide (NO) production , was studied on hypothalamic blood flow (HBF) and hypothalamic nitric oxide synthase (NOS) activity in rats. L-NAME was dissolved in the dr inking water, in a concentration of 0.1 mg/ml, and was administered fo r I week. In the chronic L-NAME pre treated animals significantly redu ced hypothalamic NOS activity and marked hypothalamic vasoconstriction were observed, the latter of which was counteracted by sustained syst emic arterial hypertension, while HBF remained unchanged. The present model of chronic NOS blockade may be useful to assess the physiologica l. functions of NO in the regulation of cerebral blood flow in the nor mally per fused brain.