The effects of chronic treatment and withdrawal of CNS depressants on aggressive behavior.

Young adult CD-1 male mice were housed in individual cages throughout the study. Groups of 10 to 20 mice were given gradually increasing doses of delta-9-tetrahydrocannabinol (THC) at 6.25 to 25 mg/kg i.p., trifluoperazine (TFP) at 6 to 12 mg/kg p.o., phenobarbital sodium (PS) at 20 to 35 mg/kg p.o., morphine sulfate (MS) at 5 to 20 mg/kg i.p., methaqualone (MQ) 10 to 20 mg/kg p.o. or chlordiazepoxide (CDP) 10 to 25 mg/kg p.o. over four to six weeks to develop tolerance of these drugs. Following the development of tolerance, the drugs were withdrawn. On the fourth day of withdrawal, a young (3-4 weeks old) male mouse was introduced into the cage. When the intensity of the attack was measured by the percentage of animals that killed the intruder within four hours. The results indicated 0 to 4 percent in the controls, 50-54 percent for THC, 50 percent for TFP, 42 percent for PS and 57 percent for MS. In contrast, no killing behavior was exhibited by these mice after treatment with MQ or CDP. These data suggest that enhanced aggressive behavior, elicited by withdrawal from certain psychotropic drugs, may be measured by the killing (muricidal) behavior of isolated mice.