To determine whether nitric oxide, which is likely endothelium-derived relaxing factor (EDRF), modulates baseline venous tone, the effects of intravenous N(G)-monomethyl-L-arginine (L-NMMA) (3-25 mg/kg), an EDRF inhibitor, on mean circulatory filling pressure (MCFP) were determined in 10 awake instrumented rats. MCFP, the equilibrated systemic pressure occurring when the circulation is arrested by transient inflation of a balloon in the right atrium, is a measure of total venous capacitance. L-NMMA caused a dose- dependent increase in mean arterial pressure and a dose-dependent decrease in heart rate. MCFP rose from 6.6 ± 0.2 to 7.6 ± 0.2 mmHg at the highest L- NMMA dose. The effects of L-NMMA on MCFP were reversed with L-arginine. In an additional four rats, in which hexamethonium was administered to induce ganglionic blockade, L-NMMA (25 mg/kg) caused a similar increase in MCFP (4.1 ± 0.6 to 5.0 ± 0.7 mmHg, P = 0.22) during the ganglionic blocked state as during the control unblocked state. These findings suggest that nitric oxide, which is likely EDRF, reduces baseline venous tone.
|Original language||English (US)|
|Journal||American Journal of Physiology - Heart and Circulatory Physiology|
|Issue number||1 34-1|
|State||Published - Jan 1 1993|
All Science Journal Classification (ASJC) codes
- Cardiology and Cardiovascular Medicine
- Physiology (medical)