SELECTIVE BILATERAL DESTRUCTION OF SUBSTANTIA-NIGRA HAS NO EFFECT ON KINDLED SEIZURES INDUCED FROM STIMULATION OF AMYGDALA OR PIRIFORM CORTEX IN RATS

Enhancement of GABAergic transmission in the substantia nigra has been shown to attenuate motor manifestations of diverse seizure models, including kindling. Similar anticonvulsant effects were reported after bilateral lesions of the substantia nigra, supporting the view that the nigra efferents constitute a critical gating mechanism in the propagation of seizure activity. However, in the lesion studies reported so far the nigra was not destroyed selectively so that regions destroyed in addition to the nigra could have been involved in the anticonvulsant effects observed. We destroyed the nigra selectively in fully kindled rats by bilateral microinjection of small amounts of the neurotoxin ibotenic acid. Two groups of rats were studied; one was kindled from stimulation of the basolateral amygdala, the other from stimulation of the piriform cortex. In both groups, there was was no indication of a reduction in seizure susceptibility, seizure severity or seizure duration after bilateral destruction of the nigra. The data thus indicate that, at least in kindled rats, the substantia nigra might be less important for seizure generation and/or propagation than previously thought. © 1990.