Role of the forebrain commissures in amygdaloid kindling

The role of the forebrain commissures in the developing and developed kindled amygdaloid seizure in the rat was investigated. In the first two experiments, bisection of the corpus callosum, hippocampal commissure, and anterior commissure prior to kindling caused a significant facilitation in the rate of primary-site kindled seizure development. In the last experiment, bisection of the corpus callosum and hippocampal commissure after primary-site kindling facilitated the subsequent rate of secondary-site kindling. It is evident, that in the intact animal, the nonstimulated hemisphere is able to exert an inhibitory influence over the development of seizure activity in a stimulated hemisphere and that this effect is, in turn, mediated via the forebrain commissures. The corpus callosum and hippocampal commissure were found to participate in the interference phenomenon since bisection of these structures either before or after primary-site kindling caused a facilitation in the rate of primary-site rekindling. In the first two experiments, an extracommissural, possibly brainstem, mechanism is suggested to mediate the transfer effect between the primary and secondary sites since bisection of the forebrain commissures prior to kindling had no effect on the rate of secondary-site kindling. The development of primary generalized motor seizures is in part dependent on the integrity of the corpus callosum and hippocampal commissure. Bisection of these structures after primary-site kindling, however, abolished the subsequent development of primary generalized seizures in a significant number of rats. Therefore, it appears that if the commissures are bisected prior to kindling, alternate pathways able to mediate the development of primary generalized seizures evolve.Medicine, Faculty ofGraduat