Conditioning of interictal behaviours, but not ictal behaviours, seizures, or afterdischarge threshold, by kindling of the amygdala in rats

Abstract

Repeated focal electrical stimulation of the brain results in kindling, the development of generalized seizures that progress in length and severity as more seizures are elicited. Barnes et al. (2001) paired one context (CS+) with kindling stimulation of the amygdala, and another context (CS-) with sham stimulation. They found conditioned anticipatory fear responses in the CS+, a conditioned place aversion to the CS+, and more intense convulsions in the CS+ than in the CS- in a probe trial. The present experiment was an attempt to replicate the findings, and to extend them by recording electroencephalographs (EEG). As well, I tested for conditioned effects on afterdischarge threshold (ADT). Rats received 45 pairings in each context before a conditioned place preference/aversion test, to determine whether the stimulation and seizures were rewarding or punishing. After more pairings, rats received suprathreshold stimulation in each context (switch test). Ictal measures in this test included afterdischarge duration, clonus duration, latency to clonus, class of convulsion, and falls. After more pairings, ADT was measured in each context. I partially replicated the findings of Barnes et al., in that conditioned anticipatory responses and conditioned place aversion were found. However, there were no conditioned effects on any ictal measures, including ADT. I conclude that conditioning is unlikely to play a major role in epileptogenesis.