Cannabis and delta-9-tetrahydrocannabinol. Effects on elements of social behaviour in mice

Behavioural effects of cannabis and delta-9-tetrahydrocannabinol (THC) in male mice encountering solvent-treated males, and of cannabis in males encountering control females, were examined by ethological procedures. Effects on elements and element-groups within behavioural categories were investigated, and effects of cannabis on the response sequence to the behaviour of male partners examined. Effects were detected on elements that previously had been grouped within categories. Flight elements "flag, evade, retreat and flee" and immobility were increased both by cannabis (50 and 100 mg/kg in male-male encounters and 25 mg/kg in male-female encounters) and by THC (5 mg/kg), whereas "scan", "wash and self-groom" and some elements of social investigation were reduced. Bout length and duration of "explore" were increased by THC. In encounters with females, cannabis decreased sexual behaviour. Sequence analysis showed that cannabis, within the limitations of the comparatively small size of sample, to have no significant effect upon normal behavioural responses at 50 and 100 mg/kg, apart from enhancement of the flight response to aggression and some elements of social investigation by partners. These more detailed analyses revealed effects that would not be detectable by the conventional approach.