Amygdaloid kindling in brainstem bisected cats.

Results of previous studies suggested that the brainstem participates in amygdaloid (AM) kindled seizure generalization and the positive transfer effect at the secondary site AM. This study was undertaken to define the role of the brainstem in the patterning of AM kindling, the maintenance of AM kindled seizure and the formation of the positive transfer effect (PTE) at the secondary site AM in cats. Seven animals with midsagittal bisection of the brainstem were subjected to primary site and secondary site AM kindling and primary site retest. All the animals were kindled at the primary site. However, the following significant differences from the pattern seen in intact animals were observed: (1) reversed direction of stage 4 seizure, with circling from the contralateral to the ipsilateral, (2) a marked kindled seizure stage instability, and (3) frequent abortive termination of the kindled seizure. At the secondary site AM, all the animals showed a complete absence of the positive transfer effect, with two out of seven animals failing to progress beyond stage 2. A negative transfer or an interference after-effect remained preserved at the secondary site kindling and primary site retest. The findings indicate that the bisected midsagittal area in the brainstem plays an important role not only in the patterning and maintenance of the kindled seizure but also in the formation of the transhemispheric positive transfer effect in feline AM kindling.