Factors that modulate inescapable shock-induced reductions in daily activity in the rat

Abstract

Most behavioral and neurochemical changes produced by inescapable shock dissipate in 1–3 days. However, daily running activity is depressed for 14–42 days following one to three sessions of inescapable shock. In the present experiments, we sought to determine whether factors known to be important in the development of the short-term effects of exposure to inescapable shock would also be important in the production of the long-term effect of inescapable shock on daily activity. Three factors were examined: a) the escapability of the shock; short-term behavioral changes generally do not occur if the shock is escapable; b) naltrexone pretreatment; the opioid antagonist naltrexone typically prevents many of the short-term behavioral sequelae of inescapable shock; c) treatment with the anxiogenic β-carboline FG-7142; administration of this compound alone frequently mimics inescapable shock in its ability to transiently disrupt behavior. The inescapable shock-induced reduction in daily activity did not depend upon escapability of the stressor. In addition, naltrexone did nor prevent and FG-7142 did not induced the reduction in daily activity associated with stressor exposure.