Environmental control of ECS-produced retrograde amnesia in goldfish.

Environmental control of ECS-produced retrograde amnesia in goldfish. PHYSIOL. BEHAV. The retrograde amnestic effect of ECS can be enhanced by exposing the goldfish to the intertrial environment for 25 mm just prior to administration of the ECS. As the interval between training and the ECS is increased, the amnesm produced by the environment-ECS interaction takes longer to develop. The environment-dependent effects of ECS relate to those of other amnestic agents which have previously been described. Amnesia Memory consolidation Shock avoidance Conditioning goldfish Electroconvulsive shock OUR LABORATORY has reported that retrograde amnesia on a shock avoidance response can be induced a day after training and hours after memory has been consolidated [6]. It is sufficient merely to replace the fish in the intertrial environment (ITE) for 25 rain just prior to administration of the agent. Stimuli in the ITE thus appears to reinstate the susceptibility of the memory to disruption. The reinstatement effect indicates that retrograde amnesia [8, 10, 13] cannot be attributed exclusively to impairment of memory consolidation. Our experiments showed an interaction between the ITE and the effects of several chemical agents, namely intracranially administered potassium chloride (KC1), puromycin, and acetoxycycloheximide, but not with electroconvulsive shock (ECS). Goldfish given the ITE-ECS treatment 24 hr post-trial showed normal memory 6 days later which was the longest retention interval tested. The present experiments were to investigate whether ECS interacts with an ITE exposure following posttrial intervals shorter than 24 hr. The results obtained with the other agents had indicated that the amnesia induced following the ITE period 24 hr posttrial develops several times more slowly than amnesia induced immediately posttrial. This suggested that the reinstatement effect is time-dependent. Increased time in the home tank prior to the ITE exposure might result in decreasing reinstatement effects, such as slower development of amnesia, and eventually complete resistance to reinstate-ment. We looked for an ITE-ECS interaction at 4 hr and 6 hr posttrial, or shortly before and after the time at which memory was otherwise fixed to the effects of ECS. METHOD Animals Goldfish 8.5-12.5 g were kept in large stock tanks for 5-14 days prior to training, and they were transferred to individual home tanks the day before an experiment. Fish were kept in continuous light, 19-20°C, and they were not fed. Shock avoidance was conditioned in individual 2-compartment shutfleboxes as previously described [6]. On Day 1 of an experiment, fish were moved …