ATTACK PRIMING IN FEMALE SYRIAN GOLDEN-HAMSTERS IS ASSOCIATED WITH A C-FOS-COUPLED PROCESS WITHIN THE CORTICOMEDIAL AMYGDALA

Allowing a resident hamster a single ''priming'' attack on a conspecif ic induces a transient aggressive arousal as indicated by a reduction in the latency and increase in the probability of attack on a second i ntruder presented within the next 30 min. We present two lines of evid ence identifying the corticomedial amygdala as an important locus medi ating this effect. (1) Attack priming significantly increases the numb er of neurons expressing immunocytochemically identified Fos protein i n the corticomedial amygdala, but not elsewhere. Pursuit and biting of an inanimate object does not induce corticomedial amygdala c-fos expr ession of the same pattern or magnitude. The corticomedial amygdala co ntribution to the priming effect involves more than a non-specific aro usal, since corticomedial amygdala c-fos expression does not correlate with locomotor activity, a standard indicator of such arousal. (2) Ra diofrequency lesions of the corticomedial amygdala reduce aggression, the greatest reduction occurring with the more anterior lesions. Other behaviors, including a priming-like locomotor practice effect in a ru nning wheel, are unaffected by corticomedial amygdala lesions. These f indings suggest that attack priming is an aggression-specific effect r esulting from a Fos-coupled change within neural circuitry of which th e corticomedial amygdala is a part. From a theoretical point of view, these experiments suggest a new approach to the analysis of the mechan isms underlying aggressive behavior and the persistence of aggressive arousal. We present a sketch of a quantitative neurobehavioral model w hich relates attack probability to neural activation within the cortic omedial amygdala. From a methodological viewpoint, these experiments e xtend the utility of mapping c-fos expression as a technique for local izing endogenous, behavior-specific processes within the central nervo us system. Copyright (C) 1996 IBRO.