Avoidance learning under delayed shock termination in prenatally x-irradiated rats.

Groups of MPI male albino rats were exposed to x-irradiation of 200 rad on Day 17 of gestation. Irradiated and control rats were trained in a shuttle box with either immediate or .5-sec delayed termination of both the electric shock (US) and the conditioned stimulus (CS) on escape trials. An avoidance response always produced prompt CS termination. Irradiated rats showed a higher degree of avoidance behaviour than controls and, under the delay condition, tended to run rapidly in the CS-US interval.