The possible role of nitric oxide (NO) on vibrissa-stimulated increase of regional cerebral cerebral blood flow (rCBF) and cerebral metabolic rate of glucose (rCMRglu) was investigated in conscious Wistar rats by using an inhibitor of NO synthase, Nc-nitro-L-arginine (NOLAG) at a concentration of 30 mg/kg. In vivo autoradiography distribution with 14C-iodoantipyrine and 14C-deoxyglucose in two separate series showed CBF of 174% of control and CMRglu of 196% of control in the primary sensory cortex opposite the stimulated side in saline treated control animals. Similar increases were found in NOLAG-treated animals. Furthermore> NOLAG did not change either basal CMRglu or CMRO2. The findings suggest, that NO is not involved in coupling flow to the increased metabolism accompanying physiological sensory stimuli.