1. The effects of alcohol (0.9 g/kg) compared with placebo (400 ml of orange juice) on plasma noradrenaline and 3,4-dihydroxyphenylethylene glycol levels, and on erect and supine blood pressures and heart rates, were studied in eight normal male volunteers.
2. Alcohol caused a rise in noradrenaline levels that commenced approximately 30 min after drinking and lasted about 4h. In contrast, 3,4-dihydroxyphenylethylene glycol levels fell immediately after alcohol administration and remained low for at least 6h. Acute alcohol administration alters noradrenaline catabolism, and may have a dual effect of increasing noradrenaline release and decreasing noradrenaline clearance.
3. Alcohol caused a transient rise in erect and supine blood pressures that preceded the rise in plasma noradrenaline. Thereafter erect blood pressures fell compared with control. This fall was associated with a progressive rise in both supine and erect rates, and reached a maximum several hours after the maximum levels of blood alcohol.
4. The major effect of acute alcohol administration is to lower blood pressure and induce a reflex tachycardia. Changes in noradrenaline and 3,4-dihydroxyphenylethylene glycol levels did not readily explain changes in blood pressure or heart rate, suggesting that alcohol induced changes in noradrenaline metabolism occur largely independent of changes in blood pressure and heart rate.
