MEASUREMENT OF THE 3 PHASES OF MURICIDAL BEHAVIOR INDUCED BY DELTA-9-TETRAHYDROCANNABINOL IN ISOLATED, FASTING RATS

Delta 9-Tetrahydrocannabinol (THC) has long been recognized as inducin g mouse-killing behavior (muricidal behavior) in starving, isolated ra ts after a single injection. We showed that when the killing tendency was increased by THC, a preliminary contact with a mouse decreased the probability of muricidal behavior. By quantifying the three phases of the muricidal behavior in either nonkiller or naive THC-treated rats, we showed that the duration of each step was notably increased as com pared to untreated natural killer rats, mainly the attack on the dead mouse, indicating increased aggressiveness. Finally, no significant ch anges were observed in the duration of the three phases in natural kil ler rats when the muricide assays were repeated every hour. In contras t, in THC-treated rats-either naive or nonkiller-all three phases decr eased with the assay repetition to levels comparable to those of natur al killer rats, suggesting that the killer behavior was progressively acquired for the six assays. These changes could be a useful model to study the central effects of THC and either its agonists or antagonist s. (C) 1998 Elsevier Science Inc.