NITRIC-OXIDE SYNTHASE INHIBITION DOES NOT AFFECT SOMATOSENSORY-EVOKEDPOTENTIALS IN THE RAT

Nitric oxide synthase (NOS) inhibition reduces the regional cerebral b lood flow (rCBF) responses to somatosensory stimulation. It is controv ersial whether this is caused by a signalling role of nitric oxide (NO ) between neurons and vascular smooth muscle, or by effects of NOS inh ibition on neuronal activity. We here report that more than 85% inhibi tion of NOS activity by topical application of the NOS inhibitor N-ome ga-nitro-L-arginine (L-NNA) for 2 h does not affect somatosensory evok ed potentials (SEPs) elicited by vibrissal deflection or electrical fo repaw stimulation in chloralose anaesthetised rats equipped with a clo sed cranial window, whereas cerebral blood Row (CBF) responses due to these stimulation paradigms are reduced by approximately 60%. We concl ude that the decrease of the regional vascular response to increased n euronal activity during NOS inhibition is not caused by a suppression of neuronal activity.