Haemodynamic actions of a nitric oxide (EDRF) synthesis inhibitor in conscious baboons (Papio hamadryas).

1. The haemodynamic effects of intravenous nitric oxide inhibitor, N-nitro-L-arginine (NOLA), were examined in four conscious non-restrained baboons (Papio hamadryas). Mean arterial pressure, (MAP), systemic vascular resistance (SVR) and cardiac output (CO) were measured at timed intervals up to 24 h after a bolus injection of NOLA. 2. N-nitro-L-arginine increased blood pressure in a dose-dependent manner up to 9.5 mg/kg. Increases in blood pressure were accompanied by increases in SVR and decreases in CO, with a significant fall in heart rate. 3. One animal received 9.5 mg/kg NOLA and became unconscious, suggesting cerebral vasospasm. 4. Vascular effects of nitric oxide contribute significantly to the regulation of arterial blood pressure under physiological conditions in the baboon.