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The aggressive behavior induced by delta9-tetrahydrocannabinol in pairs of REM sleep-deprived rats was studied in five experiments by measuring dominant and submissive behavioral patterns. When 2 REM-deprived rats received delta9-THC, one of the animals displayed very aggressive postures, while its partner assumed incomplete defensive postures. The intensity of these behavioral postures was dose-dependent. In pairs composed of one REM-deprived rat injected with delta9-THC and one normal or one REM-deprived partner injected with control solution the deprived/drugged rat showed an aggressive posture and catatonia, or a strikingly bizarre behavior, while the control partner displayed typical defensive postures. The behavioral alterations induced in REM-deprived rats by amphetamine, LSD-25, and pentobarbital failed to provoke defense postures in the normal rats paired with them; however, apomorphine partially mimicked the delta9-THC-effects. It is concluded that in REM-deprived rats delta9-THC not only provokes aggressive behavior but also impairs the defensive-submissive behavioral patterns.

The hyperresponsiveness to apomorphine disappears after REM sleep deprivation of rats; the time course of the disappearance was investigated. When REM sleep-deprived (REMd) rats were caged individually during the recovery period the increase in ambulation and in stereotyped behaviour elicited by apomorphine subsided within 8-24 h; on the other hand, the exaggerated aggressiveness persisted up to 64 days. However, when the deprived rats were allowed to recovery in groups of 3 per cage the increase in aggressiveness subsided after 4 days. Since individual housing of non-deprived rats for 4--11 days increased the apomorphine-aggressiveness steadily, 'isolation' probably summed with REM deprivation in facilitating the effects of apomorphine on aggressive behaviour. The results also suggest that the dopaminergic systems implicated in aggressive behaviour are sensitized by REM deprivation for a longer period than those subjacent to ambulation and stereotype.

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.

6-Hydroxydopamine (6OH-DA) pretreatment increased the aggressive behavior induced by marihuana in REM sleep-deprived rats. Brain catecholamine assays revealed that 6OH-DA depleted popamine (DA) and norepinephrine (NE) to a different extent, increasing the DA/NE ratio. Intraventricular injection of NE significantly decreased the aggressive behavior of these animals, whereas control solution or DA injections had no effect. The possible role played by DA and NE in the aggressive behavior induced by marihuana in REM sleep-deprived rats is discussed.

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.

1. Aggressive behaviour was elicited in rats that had been deprived of food for 20 h daily (starved), by chronic administration of Cannabis sativa extract or (-)-Delta(9)-trans-tetrahydrocannabinol.2. The influence of intraperitoneal (i.p.) or oral glucose administration, cold environment, acidosis, and corn, and protein-free diets on this aggressiveness was studied.3. Intraperitoneal injections of glucose (100-1,600 mg/kg) did not alter the aggressiveness induced by marihuana in starved rats; glucose given orally, however, blocked this behaviour.4. Low temperature (14 degrees C) strongly potentiated the aggressive behaviour induced by marihuana in the starved rats.5. Lactic acid in doses capable of potentiating thiopental anaesthesia, failed to alter the marihuana-aggressiveness of starved rats or to facilitate this effect of marihuana in rats fed ad libitum. The same negative results were obtained with ammonium chloride.6. In rats fed ad libitum with protein-free or corn diets, marihuana administered chronically did not elicit aggressive behaviour. However, aggressiveness appeared when rats were fed for only 2 h daily on those diets.7. The results suggest that the stress of hunger (and not hypoglycaemia, acidosis or lack of specific nutrients due to starvation) is the factor that facilitates the development of aggressive behaviour by chronic administration of marihuana.