Effect of oral ethanol intake on muscle sympathetic nerve activity and cardiovascular functions in humans

The aim of the present study was to clarify the acute effect of alcohol drinking on muscle sympathetic nerve activity and other cardiovascular variables in young healthy human volunteers. Seven volunteers (25.0 ± 4.7 years in age, weighing 59.9 ± 5.9 kg) were instructed to lay down on a bed, and muscle sympathetic nerve activity (MSNA) was microneurographically recorded from the tibial nerve, simultaneously with an electrocardiogram, blood pressure with Finapres® and autosphygmomanometer, cardiac output by impedance cardiography, and skin blood flow by laser Doppler flowmetry. After a 1-h rest, the subjects drank alcohol (0.6 g/kg) and were remained in resting position for 105 min. Blood ethanol levels indicated that they were moderately intoxicated. Heart rate constantly increased until 30 min after the ingestion, and maintained a peak level. MSNA was slightly but significantly suppressed just after the ingestion, and was gradually enhanced until the end of the experiment, showing a significant difference from the control level until 40 min in burst rate and until 25 min in total MSNA after the ingestion. Blood pressure showed an abrupt and transient increase at first, then gradual decrease until 30 min after the ingestion, and maintenance of the resting level until the end of the experiment. Cardiac output showed no constant tendency and no significant differences after the ingestion with wide interindividual variation. Skin blood flow increased 15 min after the ingestion. We conclude that rapidly developing disinhibitory action on medullary cardiovascular center and slowly progressive vasodilative action on peripheral vessels by ethanol contributes to the differential actions on the heart rate control and the peripheral sympathetic outflow to muscles, and configures the three-staged changes in blood pressure.