EFFECTS OF CHRONIC ETHANOL INGESTION ON MIDLATENCY AUDITORY-EVOKED POTENTIALS DEPEND ON LENGTH OF EXPOSURE

We hypothesized that chronic ethanol ingestion is associated with modi fications in components of mid-latency auditory evoked potentials (MAE Ps). To test this, male Long-Evans rats were administered 10% ethanol in drinking water as the sole fluid source for 3, 6, or 9 months. MAEP s were obtained and compared to age-matched control groups. MAEPs were obtained from additional rats after 4 weeks of abstinence. Data were obtained for varying frequencies (4, 8, 16, 24, 32 kHz) and intensitie s (65, 75, 85 dB SPL). Three months of ethanol exposure was associated with increased latencies and amplitudes of Na and Pa. MAEP components recovered and returned to control values after 4 weeks' abstinence fo llowing 3 months of EtOH exposure. Few significant differences were ob served in the ethanol-treated or abstinent group after 6 months' expos ure. However, 9 months of ethanol exposure revealed a significant incr ease in latencies and decrease in amplitudes of both Na and Pa compone nts. After 3 weeks of abstinence, the Na and Pa component peak latenci es appeared earlier than age-matched controls. The Na and Pa peak ampl itudes were slightly greater than the ethanol-treated group; however, they did not recover to control values. These findings suggest that ch ronic ethanol consumption may produce time-dependent structural and/or neurochemical alterations in substrates for cortical information proc essing, which may be irreversible. In the present paradigm, this irrev ersibility may occur after 6 or more months of ethanol intake, and may be detected with the use of MAEPs. (C) 1997 Elsevier Science Inc.