The cerebrocortical microcirculatory effect of nitric oxide synthase blockade is dependent upon baseline red blood cell flow in the rat

The effects of nitric oxide synthase (NOS) blockade on the cerebrocortical microcirculation were investigated under physiological conditions in anesth etized ventilated rats using laser-Doppler (LD) flowmetry. LD flow values o f the parietal cortex were determined before and after systemic administrat ion of the NOS inhibitor N-G-nitro-L-arginine-methyl-esther, NOS blockade r educed the LD flow significantly and the magnitude of the reduction was in close correlation with the baseline value. Synchronized sinus-wave-like LD flow oscillations were observed frequently after NOS inhibition and their a ppearance was also dependent on the high baseline flow values. These result s indicate marked, baseline-dependent differences in the cerebrocortical bl ood flow response to the inhibition of the nitric oxide pathway, and may su ggest that areas with high resting red blood cell flow express high NOS act ivity. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.