Role of nitric oxide in the CBF autoregulation during acute stage after subarachnoid haemorrhage in rat pial artery.

The present study was aimed to identify whether endogenously produced nitric oxide (NO) plays a role in preservation of cerebral blood flow (CBF) autoregulation in rat pial artery during the acute stage after subarachnoid haemorrhage (SAH). During the acute stage after SAH, the lower limit of CBF autoregulation significantly shifted to the higher arterial blood pressure in association with suppressed vasodilatation in response to acute hypotension, which was accompanied by significantly increased expression of endothelial nitric oxide synthase mRNA and increased production of superoxide anion in cerebral vessels. SAH-induced increase in superoxide production was further enhanced under pretreatment with N-nitro-L-arginine methyl ester in the cerebral vessels.