TIMID SINGLY‐HOUSED MICE: THEIR VALUE IN PREDICTION OF PSYCHOTROPIC ACTIVITY OF DRUGS

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Abstract
About 45% of singly‐housed male mice showed timidity (alert postures, running away, defensive postures) instead of aggression on interactions in pairs with group‐housed male mice, though their partners did not show any aggression. The isolation‐induced timidity was stable in repeated interactions. Timid mice also showed locomotion (walking across cage and rearing) and a small amount of sociable activity (sniffing, following partners and climbing over them). Diazepam (5 mg/kg), chlordiazepoxide (20 mg/kg), chlorpromazine (7.5 mg/kg) and barbitone (60 mg/kg) given orally inhibited the isolation‐induced timidity without reducing other motor activities in the timid mice. Imipramine lessened timidity only in a dose (80 mg/kg) which also decreased other components of behaviour in the timid isolates. (+)‐Amphetamine and lysergic acid diethylamide (LSD) increased the timid response. Comparison of the inhibition of timid activities with changes in other behaviour occurring at the same time seems a better measure of selective timidity‐reducing effects of drugs than the rota‐rod test. Diazepam (5 mg/kg) increased sociable and locomotor activities. Barbitone (20 and 60 mg/kg) increased sociable activities; however, the higher dose also evoked some aggression in timid mice. Behaviour of timid singly‐housed male mice seems to be a good measure for prediction of activity of drugs in relieving anxiety as well as for detection of aggression‐evoking and sociability‐increasing effects of drugs.