Untreated rats develop "pathological" aggression when paired with a mescaline-treated rat in a shock-elicited aggression situation

Effects of phencyclidine on aggressive behavior in mice

The effects of phencyclidine on aggressive behavior in mice and the possible mechanism of action for these effects were examined. PCP at a dose of 10.0 mg/kg significantly decreased the number of attacks by resident mice toward intruders. Significant increases in the number of attacks by non-drugged residents toward the intruders who were given high doses of PCP (6.0 and 10.0 mg/kg) were observed. Only the higher doses of PCP (6.0 and 10.0 mg/kg) significantly increased the duration of locomotion. The increase in locomotion was dependent upon the time after administration of the drug. Hyperactivity was present at 30 minutes for both doses and hypoactivity was present at three hours after administration of 3.0 mg/kg. PCP did not significantly alter the frequency of attacks in an unfamiliar test locale. Pretreatment with haloperidol (1 mg/kg) partially blocked the PCP-induced hyperactivity but pretreatment with methysergide (3 mg/kg) did not. Neither haloperidol nor methysergide blocked the suppressive effects of PCP on aggressive behavior. It is concluded that PCP does not increase aggressive behavior in mice but high doses will decrease aggression. PCP-treated intruder animals provoke more aggression by non-drugged animals. PCP-induced hyperactivity appears to be mediated by dopaminergic systems.

Drug-induced ataxia in opponents elicits "pathological" fighting in undrugged rats exposed to footshock

One member of a pair of rats was administered either mescaline, lysergic acid diethylamide (LSD), pentobarbital, or ethanol intraperitoneally twenty minutes prior to exposure to footshock in the presence of an undrugged opponent. At high doses, all drugs elicited biting from the undrugged rat of sufficient intensity to produce injury to its drugged opponent. Low doses produced species-typical fighting behavior which consisted of striking each other with their forepaws while upright and failed to elicit biting. Biting attacks by the undrugged rat were highly correlated with ataxic behavior by the drugged rat. Conversely, species-typical aggressive behavior was highly correlated with behaviors such as boxing or upright threat posture. These results suggest that drug-induced ataxic behavior may disinhibit mechanisms that regulate intra-species behavior, thus producing behavior that is more typical of inter-species aggression.

Severe aggression in rats induced by mescaline but not other hallucinogens

Pairs of male Sprague-Dawley rats were administered mescaline, lysergic acid diethylamide (LSD), psilocin, N,N-dimethyltryptamine (DMT), 3,4-dimethoxyphenylethylamine (DMPEA), or 5-hydroxydopamine (5-OHDA) IP prior to being placed in a shock-elicited aggression situation. When foot shock was delivered, controls struck each other with their forepaws, but never engaged in either biting or injurious fighting. Mescaline-treated rats (50 or 250 mg) rarely struck each other, but engaged in nearly lethal biting. While LSD (25--400 micrograms/kg), psilocin (2.0 mg/kg), and DMT (5 mg/kg) produced some biting, this did not significantly differ from controls and never resulted in injuries. At higher doses, psilocin, DMT, and DMPEA decreased the amount and intensity of fighting. Rats treated with 5-OHDA (8--200 mg/kg) or LSD (25--400 micrograms/kg) did not differ from controls. These results suggest that mescaline's ability to induce pathological aggression in rats exposed to foot shock is not shared by other hallucinogens or nonhallucinogenic mescaline analogues.

Mescaline produces pathological aggression in rats regardless of age or strain

Several measures of aggressive behavior were investigated in three ages (40-50, 90-110, and 180-200 days old) and in three strains (Sprague-Dawley, Wistar, and Long-Evans) of rats before and following the administration of mescaline hydrochloride in a shock-elicited aggression situation. The measures included the number of fights, duration of fighting, latency of fighting, number of bites inflicted, and a composite index of pathological aggression. During predrug baseline testing it was found that older rats, regardess of strain, engaged in more frequent fights that were longer in duration and more intense than younger animals. When the animals were tested with mescaline, they engaged in significantly more fights, biting, and pathological aggression than during baseline testing regardless of their age of strain. These results suggest that mescaline-induced pathological aggression in rats is a robust phenomenon.