On the generalizability of shock-elicited aggressive behavior in rats

Abstract

The aggressive behavior of rats was observed both in a colony situation and in a shockelicited aggression situation. Several aggressive behaviors seen in the colony were not observed during foots hock. Shoving and upright boxing were observed in both situations, although several components of these behaviors were missing during footshock. These data suggest that behavior elicited by footshock may be "displacement" activity rather than aggressive or defensive behavior.The shock-elicited aggression or reflexive fighting model has become the most frequently used paradigm for investigating aggressive behavior in animals . This paradigm consists of delivering brief electric footshock to a pair of rats (Urich & Azrin, 1962). When presented with this stimulus, both rats will usually assume an upright posture that consists of standing on their hind feet and facing each other with their heads tilted upward and their mouths slightly open. In this posture, they frequently strike each other with their forepaws (Miczek, 1974). While the behavior of rats in this situation has been precisely quantified and easily replicated (Powell, Frances, Braman, & Schneiderman, 1969;Ulrich, 1966), it is not clear to what degree the aggressive behavior produced by electric shock is similar to naturally occurring aggressive behavior. Some investigators Blanchard, Blanchard, & Takahashi, 1977;Moyer, 1976; Powell, Note 1) have argued that the behavioral responses elicited by footshock are primarily "defensive" and "submissive" reactions, in that they resemble the behavior of a strange rat placed into an established rat colony. Since the vast differences in housing and social history between intruder and dominant colony rats were not controlled in these studies, there are problems with this interpretation. In addition, colonies usually contain rats of both sexes. Since females are never present when two males are tested with footshock, it is not known to what degree the presence of females 372 affects the behavior of the dominant animal in the colony. The present study compares the aggressive behavior of rats in an all-male colony with the behavior elicited by footshock. METHOD SubjectsThirty-two experimentally naive male Sprague-Dawley rats, between 90 and 100 days old at the start of the experiment, were obtained from the Simonsen Breeding Laboratory, Gilroy, California, and served as the subjects for this experiment. Regardless of the type of housing, food and water were available a t all times. ApparatusThe rat colony consisted of a galvanized steel mesh chamber (l m in width by 2.0 m in length by 1.5 m in height) that was divided into two tiers of equal size to form upper and lower compartments. An inclined ramp connected the compartments and permitted the animals to move from one compartment to another.The experimental chamber used to test the animals with shock consisted of a cylinder with inside dimensions of 30 cm in diameter by 30 em in height. The entire chamber was constructed of clear Plexiglas, which allowed an unobstructed view o...