Effect of motor cortical kindling on subsequent ventral hippocampal kindling and the role of the corpus callosum in the cat.

The effect of bilateral motor cortical (MC) kindling on subsequent unilateral ventral hippocampal (VHIPP) kindling was studied in four cats with the corpus callosum (CC) intact and five cats with the CC bisected, compared with nine cats with unilateral VHIPP kindling. Subsequent VHIPP kindling in CC-intact cats resulted in the modified development of limbic seizures to ipsilateral, not contralateral, focal motor seizures in one of four cats, significantly greater seizure regressions from generalized convulsive seizure stage to earlier seizure stages and delayed onset of focal motor seizures and generalized convulsions in partial onset generalized convulsions. CC bisection reduced the degree of seizure regression from generalized convulsive seizure stage to earlier stages, facilitated the development of the last limbic seizure to the first generalized convulsive seizure, accentuated hemiconvulsions and asymmetrical generalized convulsions and delayed the onset of generalized convulsions in partial onset generalized convulsions. The modified seizure development was also induced in three of five CC-bisected cats. Results indicate that bilateral MC kindling induces inhibitory effects on subsequent unilateral VHIPP kindling and the modified ictal progress from the VHIPP to the contralateral hemispheric motor structures and also that CC bisection interferes with the bilateralization and synchronization of convulsions, but reduces the inhibition of previously established MC kindling against VHIPP kindling and facilitates the development of focal motor seizures to secondarily generalized convulsions.