Regional differences in cerebral vasomotor control by nitric oxide.

Regional differences in the role of nitric oxide in cerebral vasomotor control were investigated with a nitric oxide synthesis inhibitor, NG-monomethyl-L-arginine, or a precursor of nitric oxide, L-arginine using both dog cerebral angiography for the larger artery study and rat isolated arterioles for the microcirculation study. NG-monomethyl-L-arginine (10 mumol) constricted the dog cerebral arteries, by 15.6%, 17.5%, and 27.3% in the middle cerebral, anterior cerebral, and basilar arteries, respectively. The greater constriction of the basilar artery did not reach statistical significance. However, L-arginine (100 mumol) produced significantly greater dilation of basilar arteries than the middle cerebral or anterior cerebral (31.3% vs. 16.7% or 13.1%). NG-monomethyl-L-arginine at 10(-3) M constricted rat arterioles originating from basilar arteries significantly more than the middle cerebral arteries (23% vs. 14%). L-arginine at 10(-3) M dilated rat arterioles from basilar arteries significantly more than from the middle cerebral artery (24 vs. 11%). These findings suggest that the roles of nitric oxide in vasomotor control differs by region in the brain, and it may be greater in vessels of the posterior than of the anterior circulation.