Confirmation of whole-brain kindling with repeated subthreshold electroconvulsive shocks: A controlled study

Background: Repeated, subconvulsive electroconvulsive shock (ECS) stimuli, administered a day apart, lower the ECS seizure threshold in rats. It is not known, however, whether this kindling results from the repeated subconvulsive stimulation or from the stress induced by the experimental procedures. Materials and Methods: Adult, male Wistar rats were randomized to receive a 3-mC ECS stimulus (n = 20), a 30-V (0.3-s) footpad shock (n = 20), or sham ECS and sham footpad shock (n = 20). All procedures were conducted once daily for 3 consecutive days. On the fourth day, all rats received a 3-mC ECS stimulus. Results: At the end of the experiment, 85% of the rats in the ECS group but only 35% of the rats in each of the other two groups had experienced a seizure with the 3-mC stimulus (p < 0.001). Conclusion: The lowering of the ECS seizure threshold by repeated, once-daily subconvulsive stimuli is caused by the subconvulsive stimulation itself, not by experimental stress.