SPATIAL-LEARNING ABILITY OF RATS FOLLOWING ACUTE EXPOSURE TO ALCOHOL DURING EARLY POSTNATAL LIFE

Previous research has indicated that the developing brain is vulnerabl e to the effects of alcohol exposure. Most of this research has used a n experimental design in which animals where chronically subjected to alcohol for a lengthy period of time during gestation and/or the prewe aning period. Recent evidence has indicated that the morphology of the brain and the subsequent behaviour of the animal may also be suscepti ble to alcohol administered for a short duration during specified peri ods of development. Wistar rats were exposed to 7.5 g/kg body weight o f ethanol administered as a 10% solution via an intragastric cannula o ver an 8 h period either on the 5th (PND5) or the 10th (PND10) postnat al day of age. Gastrostomy controls received a 5% sucrose solution sub stituted 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 artific ial feeding regimes all pups were returned to lactating dams and weane d at 21 days of age. The spatial learning ability of these rats was te sted 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 su bjected to 24 trials over three days and a further trial on each of da ys 4 and 11 of the test period. Statistical analysis of the escape lat ency data revealed that both the PND5 and PND10 ethanol treated groups had significant deficits in their spatial learning ability compared w ith the control groups. However, there was no significant difference i n the degree of impairment between the PND5 and PND10 rats. It is conc luded that even short periods of alcohol exposure during brain develop ment can cause lasting impairment of spatial learning behaviour in rat s.