Dose- and time-dependent effects of ethanol on brain stem auditory evoked responses in young adult males

Abstract

In experiment 1, the dose- and time-dependent effects of ethanol on brain stem auditory evoked responses, tympanic temperature, positional alcohol nystagmus, self-ratings of intoxication and blood alcohol concentration were studied in 9 young adult males. These measures were monitored at 0.5 h intervals for high (1.0 g/kg body weight), moderate (0.5 g/kg) and placebo ethanol doses administered on non-consecutive days. The moderate and high doses of ethanol caused significant increases in latencies of brain stem potential waves II–VII, but neither dose affected their amplitudes. The latency of wave VI increased monotonically with dose but the latency changes of earlier waves were not significantly greater for the high than for the moderate dose. Ethanol also caused a small but significant decrease in tympanic temperature, also no greater for the high than for the moderate dose. However, the duration of this latter effect did increase systematically with dose. Positional alcohol nystagmus, self-ratings of intoxication and, of course, blood alcohol concentrations all increased with dose levels. Although within-subject latency changes in evoked potential peaks covaried with blood alcohol concentrations, the latter variable, along with positional alcohol nystagmus and temperature correlated higher with self-ratings of intoxication than with the latency changes. In experiment 2, an apparent withdrawal hyperexcitability, characterized by below baseline latency decreases, was observed for waves VI and VII following an ethanol dose of 0.5 g/kg. The phenomenon commenced before blood alcohol concentrations reached zero and persisted longer than the initial ethanol-induced prolongation of wave latencies.