Sustained attenuation of the cerebrovascular response to a 10 min whisker stimulation following neuronal nitric oxide synthase inhibition

We examined the effect of type I nitric oxide synthase (neuronal isoform of NOS, nNOS) inhibition on the temporal profile of the cortical blood flow ( CoBF) changes induced by a relatively long period (10 min) of whisker stimu lation. To address this issue, we used laser-Doppler flowmetry (LDF) to con tinuously monitor the CoBF in rats anesthetized with cc-chloralose, in a co ntrol condition, and 30 and 60 min following 7-nitroindazole (25 mg/kg, i.p .). Mechanical stimulation of all whiskers for 10 min led to a continuous a nd sustained CoBF increase with a mean integral response of 4030 +/- 764%. After 30 and 60 min nNOS inhibition the CoBF response was significantly red uced by 52 and 68%, respectively (P<0.05) with no evidence of any compensat ory mechanism during the whole stimulation period. These data show that reg ulation of the cerebral blood flow in response to an increased neuronal act ivity is a dynamic and tonic process in which nNOS plays an essential role. (C) 2000 Elsevier Science Ireland Ltd and the Japan Neuroscience Society. All rights reserved.