Electroconvulsive shock disrupts amygdaloid kindling: Dissociation between behavioral and electrographic events

Previous studies suggested that the elicitation of neural afterdischarge (AD) is necessary for the development of kindling. It is not clear, however, whether the activation of mechanisms underlying AD is the necessary condition for kindling development or whether such activation is an insufficient condition and propagation of the generated AD is the necessary condition for the development of kindling. To examine the question, the effect of repeated electroconvulsive shock (ECS) administration either prior to or immediately after amygdala stimulation on kindling development was evaluated. Five groups of male albino rats were implanted with a stimulating electrode with the tip in the central nucleus of the amygdala. One group received daily stimulation of the amygdala until stage 5 seizures were established. Another group received daily ECS for 18 days after which ECS was discontinued and kindling initiated. Three other groups received ECS and amygdala stimulation at different time intervals for 18 days after which only amygdala stimulation was delivered. The results showed that ECS delivered 5 min prior to amygdala stimulation depressed the responsiveness of the amygdala to stimulation and blocked the development of behavioral kindling. ECS administered 0.3 s after amygdala stimulation appeared to disrupt the propagation of AD in amygdala and cortex and also produced significant attenuation of behavioral kindling. Administered either prior to or 0.3 s after amygdala stimulation, ECS exerted minimal effects on the development of electrical events in amygdala and cortex with full length AD and postictal spike generation observed after amygdala stimulation when ECS was discontinued. Administration of ECS and amygdala stimulation at 24-h intervals did not block the development of either behavioral or electrographic events. These results suggested that both generation and propagation of AD were necessary for kindling development. In addition, dissociation between the development of behavioral kindling, AD prolongation, and postictal spiking was provided.