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

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 beta-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 not prevent and FG-7142 did not induce the reduction in daily activity associated with stressor exposure.