Nitric oxide is a potent vasodilator. Infusion of its precursor, L- arginine, results in increased cerebral blood flow (CBF) in experimental animals. We examined the effects of L-arginine infusion on CBF in humans using positron emission tomography and the quantitative H215O method. Six subjects received 500 ml of 0.9% NaCl solution, and six subjects received an infusion of L-arginine (16.7 mg/kg/min; 500 mg/kg). Before and after the i.v. infusion, paired CBF measurements were performed at baseline and with vibrotactile stimulation of the right hand. In scans performed without vibrotactile stimulation, mean wholebrain CBF increased from 34.9 ± 3.7 ml 100 g-1 min-1 to 38.2 ± 4.4 ml 100 g-1 min-1 (9.5%; p < 0.005) after L-arginine infusion. The temporal pattern of CBF changes differed from that of plasma growth hormone and insulin levels and of arterial pH. In contrast, in the saline group, mean whole-brain CBF did not change significantly (35.8 ± 5.9 ml 100 g-1 min-1 to 35.9 ± 6.4 ml 100 g-1 min-1; 0.3%). Vibrotactile stimulation produced significant focal increases in CBF, which were unaffected by L-arginine infusion. L-arginine infusion was associated with an increase in plasma L-citrulline, a byproduct of nitric oxide synthesis.
- Cerebral blood flow
- Nitric oxide
ASJC Scopus subject areas
- Clinical Neurology
- Cardiology and Cardiovascular Medicine