Effect of a subconvulsant dose of kainic acid on thresholds for phenomena elicited by electrical stimulation of sensorimotor cortex in rats.

Electrical stimulation of sensorimotor cortex was used to study early and late effects of administration of kainic acid in a dose (6 mg/kg i.p.) eliciting only nonconvulsive seizures in rats. Thresholds for elicitation of four phenomena--movements directly related to stimulation; epileptic afterdischarges (ADs) of the spike-and-wave type; clonic seizures accompanying these ADs; and mixed type of ADs where spike-and-wave activity transgresses into limbic type of epileptic phenomena--were measured. Acute administration of kainic acid resulted in a decrease of the threshold for elicitation of mixed type of ADs. In contrast, 1 week after kainic acid administration, the thresholds for stimulation-bound movements, spike-and-wave ADs and concomitant clonic seizures were increased, but the threshold for mixed type of ADs remained unchanged. The changes in thresholds tended to decrease 2 weeks after kainic acid but statistical significance was reached only for stimulus-bound movements. In addition, repetition of stimulation series after 1 as well as 2 weeks markedly influenced the thresholds.