Biphasic action of ethanol

Physiological, behavioral, and biochemical evidence demonstrating the excitatory and depressant effects of ethanol in man and experimental animals is reviewed. An excitatory action is noted on exposure of an organism to low doses of ethanol. Thus stimulatory effects of ethanol on motor activity, various behaviors, EEG activation, and gastric acid secretion are well documented. A stimulatory effect of ethanol is also noted as a delayed response (after 7–18 hr) with large doses of ethanol. Examples here include seizure susceptibility, some neurotransmitter mechanisms (norepinephrine, acetylcholine), and sensitivity to pain. It is likely that differences in dosage and of the time of observation after ethanol treatment have contributed to some extent to the variability of results reported in the literature. Some implications and possible mechanisms for the biphasic actions of ethanol are discussed.