Influence of electroconvulsive shock and naloxone on acquisition and retention of a spatial navigation task in rats.

The effects of electroconvulsive shock (ECS) on learning and memory were examined in rats using the Morris navigation task. Rats were trained to escape from a large pool of water onto an invisible underwater platform. Application of ECS at various intervals before training (15 to 120 min) induced a significant time-dependent impairment of the acquisition of escape behavior; naloxone (1 mg/kg IP 15 min before ECS) did not prevent the ECS-induced impairment. One single active escape trial preceding ECS prevented ECS-interference with the subsequent acquisition of the task. Spatial navigation in well trained animals was significantly impaired 30 and 60 min after ECS. It is concluded that ECS disturbs the disturbs the formation of a spatial memory trace more than the retrieval of a previously formed spatial trace. Release of opioid peptides do not seem to contribute substantially to the amnesic effects of ECS in the spatial navigation task.