Alcohol increases both locomotion and immobility in mice: an ethological analysis of spontaneous motor activity.

The effects of alcohol on locomotor activity of group- and individually-housed mice were studied using direct ethological observations, including a detailed postural analysis and measures of both locomotion and immobility. Ethanol (0, 0.5, 1.0 and 2.0 g/kg, IP) was given to subjects placed alone in a novel cage, and videotape recordings of behaviour were made. Locomotor activity was unchanged or increased by alcohol administration. Immobility was profoundly increased, however, at both the intermediate and high doses of alcohol, so that there was a simultaneous increase in measures of both locomotion and immobility. These increases were possible because of a decrease in certain active but non-locomotor elements of behaviour, such as rearing and digging. There generally appeared to be little effect of differential housing, although blood alcohol levels were significantly higher in group-housed animals. This depressant effect of alcohol would probably not be detected by simply recording locomotor activity, since ambulation itself was unchanged or increased. Measurements of both locomotion and immobility may thus more accurately detect stimulant and depressant effects of drugs.