OPPOSITE EFFECTS OF L-ARGININE AND NITROGLYCERIN ON CEREBRAL BLOOD VELOCITY - NITRIC-OXIDE PRECURSORS AND CEREBRAL BLOOD VELOCITY

Nitric oxide (NO), a gaseous molecule synthesized in the arteriolar en dothelium from the amino acid L-arginine (L-arg), has been identified as the previously described Endothelium-Derived Relaxing Factor (EDRF) ; nitroderivatives such as nitroglycerin are known to induce vasodilat ion via NO release, The aim of this study was to evaluate by Transcran ial Doppler (TCD) monitoring any changes in cerebral hemodynamics indu ced by both the infusion of L-arg and the sublingual administration of nitroglycerin in 20 healthy subjects. L-arg infusion induced a signif icant increase in blood velocity compared to the baseline value (mean +/- S.D. percent change = 18 +/- 8.71; p < 0.0001) and a slight but si gnificant decrease in Pulsatility Index. By contrast, nitroglycerin wa s able to cause a significant decrease in blood velocity (mean +/- S.D . percent change = 24.8 +/- 7.68; p < 0.0001), while leaving Pulsatili ty Index unchanged. These data suggest that L-arg and nitroglycerin, b oth hypothesized to use NO as the final product at the vascular level, result in opposite blood velocity patterns within the cerebral circul ation. This may be due to the particular type of artery and/or to the local endothelial environment whereby the released NO may act. (C) 199 7 Elsevier Science B.V.