Spatial learning ability of rats following acute exposure to alcohol during early postnatal life

Previous research has indicated that the developing brain is vulnerable to the effects of alcohol exposure. Most of this research has used an experimental design in which animals where chronically subjected to alcohol for a lengthy period of time during gestation and/or the preweaning period. Recent evidence has indicated that the morphology of the brain and the subsequent behaviour of the animal may also be susceptible to alcohol administered for a short duration during specified periods of development. Wistar rats were exposed to 7.5 g/kg body weight of ethanol administered as a 10% solution via an intragastric cannula over an 8 h period either on the 5th (PND5) or the 10th (PND10) postnatal day of age. Gastrostomy controls received a 5% sucrose solution substituted isocalorically for the ethanol. Another set of pups raised by their mother were used as ‘suckle controls’. All surgical procedures were carried out under halothane vapour anaesthesia. After the artificial feeding regimes all pups were returned to lactating dams and weaned at 21 days of age. The spatial learning ability of these rats was tested in the Morris water maze when they were between 41–54 days of age. This task requires the rats to swim in a pool containing water made opaque and locate and climb onto a submerged platform. The time taken to accomplish this is known as the “escape latency.” Each rat was subjected to 24 trials over three days and a further trial on each of days 4 and 11 of the test period. Statistical analysis of the escape latency data revealed that both the PND5 and PND10 ethanol treated groups had significant deficits in their spatial learning ability compared with the control groups. However, there was no significant difference in the degree of impairment between the PND5 and PND10 rats. It is concluded that even short periods of alcohol exposure during brain development can cause lasting impairment of spatial learning behaviour in rats.