[Depressive effects of benzodiazepines on penicillin-induced epileptic discharges]

Effects of clonazepam, nitrazepam and diazepam on penicillin induced primary, spread and reactive epileptoform discharges were investigated in gallamine immobilized cats. Different strengths of seizure foci were induced by penicillin G 1000, 3000 and 6000 U injected into the cortex, amygdala and intralaminal thalamus, and the spread of epileptic discharges in the subcortex or surrounding area and to the contralateral area was followed. Benzodiazepines 5 mg/kg i.v. shortened the duration of primary epileptoform discharges and prolonged the interictal interval in the cortical, amygdaloid and intralaminal thalamic epileptogenesis induced by a high concentration of penicillin G. When a low concentration of penicillin G was injected into the cortex, amygdala and intralaminal thalamus, benzodiazepines abolished the spread of primary epileptoform discharges and the reactive discharges, but did not suppress completely the primary epileptogenic discharges and the contralateral reflective activity. Suppression of the discharges necessitated administration of a high dose. The greatest degree of suppression was seen with clonazepam. It is concluded that the anticonvulsive effect of benzodiazepines may be due to the blackades of neuronal pathways which spread the seizure discharges from the site of origin (focus) to the effector organ, and the elevation of convulsive thresholds.