Cannabis, catecholamines, rapid eye movement sleep and aggressive behaviour.

1. Previous work from our laboratory has shown that cannabis induces aggressive behaviour in rats that have been deprived of rapid eye movement (REM) sleep. It was suggested that this effect was related to brain catecholamines, with dopamine playing an agonist role and noradrenaline an inhibitory one. The present paper describes new experiments dealing with this subject. 2. Previous REM sleep-deprivation enhanced both delta9-tetrahydrocannabinol (THC)-induced hypothermia and nomifensine effects on aggressive behaviour. 3. A marihuana extract decreased brain dopamine turnover in REM sleep-deprived rats, an effect not observed in non-deprived rats. Noradrenaline metabolism was not altered. 4. Fighting behaviour was elicited in REM sleep-deprived rats treated with 4 different dopamine-beta-hydroxylase inhibitors. 5. Apomorphine, nomifensine and delta9-THC administered to non-deprived rats pretreated with bis(4-methyl-1-homopiperanzinyl-thiocarbonyl) disulphide (Fla-63), induced fighting behaviour. 6. Nomifensine and apomorphine induced fighting in non-deprived rats pretreated with delta9-THC. 7. Clonidine inhibited the fighting elicited in REM sleep-deprived rats by either delta9-THC or Fla-63 pretreatment. 8. The data are discussed in terms of the influence of REM sleep-deprivation (or the stress associated with deprivation) on the response to dopaminergic drugs and cannabis. Taken together they emphasize the participation of brain dopamine and noradrenaline systems in the aggressive behaviour studied.