Response variability of ethanol-induced locomotor activation in mice

Mice from a randomly bred strain were divided into two groups according to their locomotor responses to ethanol (0.8-3.0 g/kg): in two thirds of the tested animals ethanol increased locomotor activity (ethanol activated-EA), whereas in the remaining one third it did not (ethanol non-activated-ENA). Both groups did not differ in their locomotor activity after saline administration. Furthermore, EA and ENA mice presented a similar increase in locomotor activity after challenge with 1.0 and 2.0 mg/kg d-amphetamine. Chronic exposure to ethanol increased the ethanol-induced locomotor activation in both EA and ENA groups. The possibility that the lack of responsiveness of ENA mice to ethanol's acute activating effect could be due to a higher sensitivity to the depressant effect of ethanol is discussed.