Genetic influences on the effects of alcohol on auditory evoked potentials

Effects of alcohol on auditory evoked potentials were examined in 77 subjects without a history of alcohol abuse. Subjects were monozygotic twins, dizygotic twins, siblings, and adoptees, all same-sexed and reared together. Alcohol was administered to achieve 0.1 g/dl blood levels. Ten additional control subjects received placebo doses. The amplitude of the P50 wave of the auditory evoked response was reproducibly diminished in alcohol-treated subjects compared to controls. Evoked potentials were recorded in a conditioning-testing paradigm, which uses paired stimuli. The second or test response is decremented compared to the first or conditioning response. The paradigm thus examines gating of response to sensory stimulation. In addition to the alcohol-induced decrease of the P50 amplitude in the conditioning response already noted, the ratio of the P50 test response amplitude to the conditioning response amplitude increased after alcohol. This change, reflective of decreased sensory gating, was variable between subjects, but showed high test-retest reliability. These effects of alcohol on P50 amplitude and its decrement in the conditioning-testing paradigm were used to examine possible genetic influences on sensitivity to alcohol. The latter parameter showed significantly higher correlations in monozygotic twins than in siblings or adoptees; dizygotic twins had intermediate values. The results suggest that alcohol's effects on suppression of P50 in the conditioning-testing paradigm may be genetically influenced.