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 alcoho l drinking on muscle sympathetic nerve activity and other cardiovascul ar variables in young healthy human volunteers. Seven volunteers (25.0 +/- 4.7 years in age, weighing 59.9 +/- 5.9 kg) were instructed to la y down on a bed, and muscle sympathetic nerve activity (MSNA) was micr oneurographically recorded from the tibial nerve, simultaneously with an electrocardiogram, blood pressure with Finapres(R) and autosphygmom anometer, cardiac output by impedance cardiography, and skin blood flo w by laser Doppler flowmetry. After a 1-h rest, the subjects drank alc ohol (0.6 g/kg) and were remained in resting position for 105 min. Blo od ethanol levels indicated that they were moderately intoxicated. Hea rt rate constantly increased until 30 min after the ingestion, and mai ntained a peak level. MSNA was slightly but significantly suppressed j ust after the ingestion, and was gradually enhanced until the end of t he experiment, showing a significant difference from the control level until 40 min in burst rate and until 25 min in total MSNA after the i ngestion. Blood pressure showed an abrupt and transient increase at fi rst, then gradual decrease until 30 min after the ingestion, and maint enance of the resting level until the end of the experiment. Cardiac o utput showed no constant tendency and no significant differences after the ingestion with wide interindividual variation. Skin blood flow in creased 15 min after the ingestion. We conclude that rapidly developin g disinhibitory action on medullary cardiovascular center and slowly p rogressive vasodilative action on peripheral vessels by ethanol contri butes to the differential actions on the heart rate control and the pe ripheral sympathetic outflow to muscles, and configures the three-stag ed changes in blood pressure.