Ipsilateral hemiconvulsive seizure after unilateral injection of procaine into the substantia innominata of amygdaloid-kindled rats.

The effects of procaine injected into the substantia innominata (SI) and the amygdala (AM) were compared in AM-kindled rats. Intra-SI injection of procaine (ipsilateral to the kindled AM) caused immediate contralateral hemiparesis lasting for about 30 min, associated with EEG amplitude reduction. When the kindled AM was stimulated at the previously established generalized seizure triggering threshold (GST), 8/15 animals had ipsilateral hemiconvulsive seizure 5 min after the injection. In all the animals, afterdischarge was readily produced with a significant reduction in its duration. When procaine was injected into the kindled AM, there was no paresis or EEG change. AM stimulation at the GST did not evoke afterdischarge 5 min after the injection, although the kindled seizure was reactivated by a more intense stimulus. After 24 hr, all the animals, regardless of the site of procaine injection, responded to GST stimulation with a kindled seizure. The data suggest that: (1) the effect of intra-SI procaine is not due to drug diffusion to the kindled AM, and (2) the kindled AM can gain access to the contralateral hemispheric motor mechanism without participation of the ipsilateral SI.