Suppression of mouse killing and apomorphine-induced social aggression in rats by local anesthesia of the mystacial vibrissae.

Local anesthesia of the facial epidermis can effect a substantial decrease in shock-elicited fighting of paired rats. The present experiments constitute methodological extensions to mouse killing and spontaneous drug-induced social aggression. In the first experiment, known mouse-killing rats were given bilateral lidocaine or placebo injections administered under ether anesthesia. Attack and kill latencies were significantly longer under lidocaine than under placebo; all subjects killed under placebo, whereas a third of all subjects failed to kill on the initial lidocaine test. On subsequent lidocaine testing, latencies decreased and nonkilling rats killed. In a second experiment intense apomorphine-induced conspecific fighting of rats preselected for aggressiveness was markedly reduced following lidocaine anesthesia. The comparative results of both experiments are interpreted in reference to theoretical assertions regarding the import of sensory information in stimulus-bound attack and the typology of central aggression systems.