Effect of serotonergic drugs on the aggressiveness induced by delta 9-tetrahydrocannabinol in rem-sleep-deprived rats.

1. delta 9-Tetrahydrocannabinol (THC) induced aggressive behavior in rats previously deprived of REM sleep. This aggressiveness was significantly potentiated by tryptophan and fluoxetine, drugs which increase brain serotonin availability. 2. Conversely, drugs which decrease serotonergic function such as D,L-p-chlorophenylalanine, cinanserin and cyproheptadine strongly blocked the aggressive behavior. 3. On the basis of previous data indicating an involvement of dopaminergic mechanisms in this type of aggressiveness and the present results showing a role for serotonin, it is concluded that REM deprivation-THC aggression is under the control of at least these two neurotransmitters.