PharmacologyBiochemistry & Behavior, Vol. 17, pp. 263-269, 1982.Printedin the U.S.A. Stimulus Change Influences Escape Performance: Deficits Induced by Uncontrollable Stress and by Haloperidol HYMIE ANISMAN AND ROBERT M. ZACHARKO Department of Psychology, Unit for Behavioral Medicine and Pharmacology Carleton University, Ottawa, Ontario K1S 5B6 Received 25 July 1981 ANISMAN, H. AND R. M. ZACHARKO. Stimulus change influences escape performance: Deficits induced by uncon- trollable stress and by haloperidol. PHARMAC. BIOCHEM. BEHAV. 17(2)263--269, 1982.--Exposure to uncontrollable foot-shock or treatment with haloperidol was found to disrupt subsequent escape behavior. Performance among naive mice, as well as mice that had been exposed to inescapable shock or treated with haloperidol could be enhanced by either interrupting the shock train during escape testing or by presentation of a novel stimulus. The effectiveness of these treatments were dependent on the time at which the change in stimulation occurred. That is, shock interruption or cue presentationjust prior to escape being possible enhanced performance, but the same manipulation several seconds prior to escape being possible had only a limited effect. In addition, the time of cue termination also influenced escape behavior. When cue offset coincided with or followed successful escape a performance enhancement was evident, but when cue offset occurred several seconds prior to escape, performance was not affected. It was suggested that inescapable shock and haloperidol treatment hinder performance by disrupting response maintenance. Shock interruption and novel cue presen- tation minimize disturbances of escape performance by altering the course of the decline of shock-elicited activity. Escape performance Stress Haloperidol Foot-shock EXPOSURE to uncontrollable shock has repeatedly been shown to induce pronounced deficits of later escape behav- ior [2, 10, 17]. Whereas some investigators have attributed the performance disruption to cognitive changes (i.e., learned helplessness) provoked by the uncontrollable stress [10], others have contended that difficulties in response ini- tiation and maintenance are responsible for the behavioral disturbance [2, 5, 17]. These motor disturbances are thought to reflect either learned competing response tendencies [2, 7, 8] or are a consequence of the depletion of brain catechola- mines engendered by the inescapable shock [4, 14, 16, 17]. Discrete analyses of the behavior of animals during expo- sure to inescapable shock have revealed a characteristic profile of shock-elicited activity, i.e., activity measured dur- ing shock itself [2]. Upon shock inception mice exhibited a transient (2-3 sec) period of vigorous responding, followed by a period of limited active responding. Among mice that had previously been exposed to inescapable shock the period of excitation was truncated, and response immobility be- came particularly pronounced. The transient excitation seen upon shock inception is thought to favor adequate escape behavior in a task where escape was possible soon after shock onset. However, if the response could not be com- pleted quickly, the depression of motor activity would favor poor escape behavior, particularly among animals that had previously been exposed to inescapable shock. The pattern of shock-elicited activity, and hence escape behavior, could be modified through a manipulation as sim- ple as briefly interrupting the shock train [2]. Moreover, casual observation of mice in this laboratory has revealed that any number of extraneous cues would disrupt the ster- eotyped immobility evident during long-duration shock pre- sentations and would provoke efficient escape behavior. One purpose of the present investigation was to document the effects of a novel cue on escape behavior among experi- mentally naive mice and among mice that had been exposed to uncontrollable shock. The second purpose of the current investigation was to determine whether shock interruption or presentation of a novel stimulus would alter the escape defi- cits introduced by the dopamine receptor blocker, haloperi- dol. It has been suggested [5] that the deficits in response initiation and maintenance induced by uncontrollable shock are reminiscent of the motoric effects induced by haloperi- dol. As such, manipulations that alter the effects of inescap- able shock would be expected to alter the behavioral conse- quences produced by treatment with haloperidol. tSupported by Grants A8905 and MA6486 from the Natural Sciehce and Engineering Research Council and the Medical Research Council of Canada. Requests for reprints should be sent to Hymie Anisman, Unit for Behavioral Medicine and Pharmacology, Department of Psychol- ogy, Carleton University, Ottawa, Ontario, K1S 5B6, Canada.