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 stimulation. To address this issue, we used laser-Doppler flowmetry (LDF) to continuously monitor the CoBF in rats anesthetized with α-chloralose, in a control 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 and sustained CoBF increase with a mean integral response of 4030±764%. After 30 and 60 min nNOS inhibition the CoBF response was significantly reduced by 52 and 68%, respectively (P<0.05) with no evidence of any compensatory mechanism during the whole stimulation period. These data show that regulation of the cerebral blood flow in response to an increased neuronal activity is a dynamic and tonic process in which nNOS plays an essential role.