Plus-maze behavior and susceptibility to 3-mercaptopropionate-induced seizures in rat lines selected for high and low alcohol sensitivity.

Selective outbreeding for high and low acute alcohol sensitivity has produced two rat lines (alcohol-sensitive ANT and alcohol-insensitive AT lines) that also differ in their sensitivity to GABAergic drugs, benzodiazepines and barbiturates. These rats were now compared in two behavioral tests believed to involve central GABAergic mechanisms, in elevated plus-maze test and in 3-mercaptopropionate-induced seizure test. The AT animals spent more time in the open arms of the plus-maze than the ANT rats, suggesting that the AT's behave less anxiously. The ANT's were more susceptible to seizures induced by 3-mercaptopropionate (50 mg/kg, IP) than the AT's, suggesting the ANT's having greater sensitivity to a decrease in brain GABA concentration. At the time of the first seizure signs, there was a tendency, though a nonsignificant one, to greater decreases in brain GABA in the ANT's than AT's. These results suggest that there are differences in GABA-related behaviors between ethanol-naive rats of the lines produced by selective outbreeding for differences in alcohol sensitivity. In theory, these behavioral line differences might physiologically counteract alcohol effects in the ANT's and enhance them in the AT's. In elevated plus-maze test, however, an acute dose of ethanol (1 g/kg, IP) significantly changed the behavior of the ANT animals, but only up to level of the AT rats. The apparent sensitivity to ethanol may thus be dependent on the naive behavior of the alcohol-insensitive AT and alcohol-sensitive ANT rats.