[Function of ECS as a cue in retrograde amnesia in the rat]

Two experiments were performed with rats to examine whether electroconvulsive shock (ECS), which is known to produce retrograde amnesia (RA), would serve as a dominant cue in the training trial. In Experiment I, after 6, 1, or 0 ECS preexposures , rats were received ECS immediately following one-trial passive avoidance training in a step through apparatus. Twenty-four h later, six ECS preexposure group showed a higher level of retention performance. Thus, the effects of ECS on RA were shown to be attenuated by the preexposure to ECS. In Experiment II, it was shown that ECS acquired a considerable amount of cue value which might produce a conditioned suppression on an off-the-baseline type procedure. These results were interpreted as that RA phenomena could be considered as a sort of retroactive conditioning where ECS served as a CS.