Periadolescent alcohol exposure has lasting effects on adult neurophysiological function in rats

Most individuals have their first experience with ethanol (EtOH) consumption as adolescents. Episodes of high EtOH drinking, lasting from hours to days (i.e. binges), are not uncommon. Thus, adolescent EtOH drinking has become a significant health concern due to the possible protracted effects of high doses of EtOH on behavior and the developing brain. This study assessed the effects of brief high levels of EtOH during periadolescence on subsequent behavior and electrophysiology in adult rats. Male Sprague-Dawley rats were exposed to EtOH vapor for 5 days (i.e. postnatal days 35-40) or 10 days (i.e. postnatal days 30-40) for 12 h/day. Locomotor activity, EEG activity, and event-related potentials (ERPs) were then assessed at 1 and 6-7 weeks post EtOH exposure. Significant differences in locomotor activity were not observed at 1 week or 6-7 weeks post-ethanol exposure. However, EtOH exposure did have long-term electrophysiological effects. EtOH exposure increased the frequency of the EEG in the 1-2 Hz range in the parietal cortex and the 16-32 Hz range in the hippocampus. EtOH exposure also increased hippocampal N2 amplitude, decreased hippocampal P3 amplitude, and decreased cortical and hippocampal P2 amplitudes. While these findings are generally similar to those reported following long-term ethanol exposure during adulthood, alcohol exposure during adolescence appears to produce more robust hippocampal effects following shorter periods of exposure. In addition, these data indicate that, in the absence of overt behavioral differences, there are long-lasting changes in the functional brain activity of adult rats briefly exposed to high levels of EtOH during the periadolescent period.