EFFECTS OF ETHANOL, MK-801, AND CHLORDIAZEPOXIDE ON LOCOMOTOR-ACTIVITY IN DIFFERENT RAT LINES - DISSOCIATION OF LOCOMOTOR STIMULATION FROM ETHANOL PREFERENCE

Several lines of research have suggested a link between the reward val ue of a drug and its ability to stimulate locomotion. One goal of the present study was to determine whether ethanol preferentially stimulat es locomotor activity in lines of rat that show a preference for ethan ol. A secondary goal was to determine the extent to which the benzodia zepine-like and NMDA antagonistic action of ethanol accounted for its effect on locomotor activity. To meet these goals, the effects of vary ing doses of ethanol (0.125-1.0 g/kg), MK-801 (0.1-0.3 mg/kg), and chl ordiazepoxide (0.3-3 mg/kg) on locomotor activity were studied in seve ral lines of rats that had been habituated to the testing procedure. T he effect of low doses of ethanol on motor activity in the Alcohol-Pre ferring (P) and Fawn-Hooded rats, which show a strong ethanol preferen ce, were similar to those of the alcohol-nonpreferring (NP), Flinders Sensitive Line, and Flinders Resistant Line rats. Only the Flinder Res istant Line rats showed a small, but significant increase in locomotor activity after the administration of ethanol. The highest dose of eth anol (1.0 g/kg) produced locomotor depression in all lines except the P and NP lines, which were not tested at this dose. These findings do not support a link between locomotor stimulation by ethanol and ethano l preference. In contrast, all lines exhibited locomotor stimulation a fter moderate (0.1-0.3 mg/kg) doses of MK 801, but did not exhibit inc reases in activity following any dose of chlordiazepoxide. These data indicate that the profiles of activity after MK 801 and chlordiazepoxi de were distinct from that of ethanol in the various rat lines. Theref ore, the effects of ethanol on locomotor activity cannot be accounted for by reference solely to its antagonist-like action at NMDA receptor s and/ or its agonist-like action at GABA/benzodiazepine receptors.