Alcohol use in children and adolescents is widespread. However, very little is known about the effects of alcohol exposure during this period of postnatal development. The goal of the present study was to compare the relative sensitivity to the sedative effects of alcohol in periadolescent and adult rats. After treatment with either 4 or 5 g/kg ethanol, both 20- and 30-day-old rats regained their righting reflex significantly earlier than 60-day old rats. In 30-day-old rats, serum ethanol concentrations (SECs) were significantly greater at the time of the recovery of the righting reflex than 60-day-old rats. Developmental differences in the effects of ethanol on locomotor activity were also observed. In 60-day-old rats, 2.5 g/kg ethanol generally decreased locomotor activity. Ethanol did not significantly alter locomotor activity in 20- and 30-day-old rats. Finally there were significant developmental differences in the pharmacokinetics of ethanol with a significant delay in the time to peak SECs in 60-day-old rats relative to 20- and 30-day-old rats. These findings indicate that peri-adolescent rats are less sensitive to the sedative effects of ethanol as they recovered their righting reflex earlier and at significantly higher SECs than adult rats.

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Previous studies have shown that ethanol inhibits memory-related synaptic activity and plasticity more potently in hippocampal slices from immature rats, compared with those taken from adults. We therefore hypothesized that ethanol would more potently attenuate the acquisition of spatial memory in adolescents, compared with adult rats. Adult (65 days of age) and adolescent (30 days of age) male rats were given five daily trials on a spatial memory task in a Morris Water Maze. The animals from each age group were subdivided into three subgroups. Each day, thirty minutes before training, the animals in each subgroup were given an intraperitoneal injection of 1.0 g/kg of ethanol, 2.0 g/kg of ethanol, or the saline vehicle. Training continued daily until the control animals had reached a performance criterion. Ethanol treatment significantly impaired spatial memory acquisition in the adolescent rats, but did not impair acquisition in adult rats. A separate experiment with identical treatment groups showed that ethanol did not impair acquisition of a nonspatial memory task in the water maze in animals from either age group. These experiments show that the acquisition of spatial, but not nonspatial, memory is more potently impaired by ethanol in adolescent animals, compared with adults.