Conditioned avoidance acquisition and extinction following repeated electroconvulsive shock: strain effect and response to vasopressin

Male albino rats (Sabra strain) were exposed to electroconvulsive shock (ECS) once daily for periods ranging from 1 to 13 days, and proactive effects on conditioned avoidance response (CAR) acquisition and extinction were studied. CAR acquisition was intact following both single and repeated ECS, but extinction was accelerated by multiple ECS administration. These findings resembled the effect of repeated ECS on anterograde memory function in humans and confirmed previous observations based on a passive avoidance paradigm. However, extinction was not accelerated in a different rat strain (LC2). Parallel open field activity measures suggested that these findings were not related to ECS-induced alterations in locomotor activity. Administration of arginine vasopressin prior to each ECS, or following acquisition sessions, as well as 1-desamino-8-D-arginine vasopressin administration following acquisition sessions, did not ameliorate ECS-induced deficits in the Sabra rats. Differences between the present paradigm of ECS administration and those in which positive effects of vasopressin and other neuropeptides have been reported are discussed. The potential research applications of a rodent model of ECS-induced memory impairment that parallels deficits encountered in the clinical context are considered.