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Summary:Purpose: Lesions of the claustrum in cats and primates have been shown to disrupt the development and expression of amygdaloid-kindled seizures in cats and primates. Because the structure and connectivity of the claustrum can vary between species, we wanted to examine the effects of claustral lesions on kindling in rats.Methods: One group of rats received bilateral radiofrequency lesions of both anterior and posterior regions of the claustrum before amygdaloid kindling. Another group of rats received bilateral anterior and posterior radiofrequency lesions of the claustrum after amygdaloid kindling. Some rats were tested for transfer of kindling to the contralateral amygdala after claustral lesions.Results: Small lesions that destroyed 13% of the claustrum were capable of delaying, but not blocking, amygdaloid kindling. The delay in kindling was due to an increase in the stimulation trials required to kindle to stage 5 seizures. The lesions had no effect on established kindled seizures or on transfer to the contralateral amygdala.Conclusions: As in other species, the claustrum in the rat appears to play a role in kindling from the amygdala. Because of the restricted size of our claustral lesions, however, we were unable to conclusively assess the full extent of the claustrum's participation in limbic kindling.

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Controversy surrounds whether aberrant mossy fiber sprouting in the hippocampus is necessary for the establishment of seizure states. We investigated the association between mossy fiber sprouting and kindling in guinea-pigs, using either single-site or alternate-site stimulation. Kindling with single-site amygdaloid stimulation did not induce significant sprouting, despite the development of partial seizures. In contrast, single-site septal and alternating amygdaloid-septal stimulation produced moderate but significant sprouting in about 60% of animals that failed to develop stage 5 generalized seizures. Since the magnitude of sprouting was similar despite striking differences in the intensity of seizures that developed, we conclude that mossy sprouting is not causally associated with seizure development.

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