The anterograde effect of ECS on the acquisition, retrieval and extinction of conditioned taste aversion.

Conditioned taste aversion was established in rats by spontaneous or forced drinking of saccharin (0.1%, CS) followed after 30 min by poisoning (0.15 M LiCl, 2% body weight, US) and retention was tested by offering the animals saccharin 1 or 2 days later. ECS (50 Hz, 50 mA, 0.5 s) applied 120, 60, 30 or 15 min before saccharin administration elicited an increasing disruption of CTA acquisition which was complete with the 15-min ECS-CS interval. On the other hand, ECS applied 2, 15 or 30 min after saccharin drinking caused either no or only moderate CTA disruption. ECS applied 30 min before retention testing reduced the fluid intake but did not prevent CTA retrieval. Forced feeding saccharin to rats with a strong CTA, established by repeated saccharin-LiCl pairing, caused CTA extinction which was only slightly decreased by ECS applied 10 or 60 min before the extinction trial. The proactive ECS effects prevent formation of the short-term gustatory trace but do not seriously disrupt the gustatory trace-poisioning association and leave the CTA retrival and extinction unaffected. In this respect ECS resembles other procedures that differentially interfere with CTA acquisition and retrieval, particularly the effect of paradoxical sleep deprivation.