Kindling of claustrum and insular cortex: comparison to perirhinal cortex in the rat

The perirhinal cortex has recently been implicated in the kindling of limbi c generalized seizures. The following experiments in rats tested the select ivity of the perirhinal cortex's epileptogenic properties by comparing its kindling profile with those of the adjacent insular cortex, posterior (dors olateral) claustrum and amygdala. The first experiment examined the kindlin g and EEG profiles, and found that both the claustrum and insular cortex de monstrated rapid epileptogenic properties similar to the perirhinal cortex, including very rapid kindling rates and short latencies to convulsion. Fur thermore, electrical stimulation of all three structures led to a two-phase progression through stage-5 seizures which had characteristics of both neo cortical and amygdaloid kindling. In a second experiment rats were suspende d in a harness to allow for more detailed documentation of both forelimb an d hindlimb convulsions. With this procedure we were able to detect subtle y et unique differences in convulsion characteristics from each of the kindle d sites and stage-5 seizure phases. Some of these convulsive parameters wer e correlated with changes in FosB/Delta FosB protein and BDNF mRNA expressi on measured two hours after the last convulsion. Overall, it appears that t he perirhinal cortex is not unique in its property of rapid epileptogenesis . Moreover, the posterior claustrum exhibited the fastest kindling and most vigorous patterns of clonus, suggesting that it may be even more intimatel y associated with the motor substrates responsible for limbic seizure gener alization than is the perirhinal cortex.