Potentiation and modification of recruiting responses precedes the appearance of spike and wave discharges in feline generalized penicillin epilepsy.
Recruiting responses (RR) were evoked by stimulation of nucleus centralis medialis in awake and painlessly immobilized cats. Following the administration of sodium penicillin G (350,000 IU/kg i.m.) and at a time preceding the development of generalized spike-and-wave discharge we observed a strong potentiation of RR in 10 out of 15 experiments (50-200% increase in amplitude). The major feature of wave form modification consisted mainly of a development or increase of positive phases of individual recruiting waves. In between such large amplitude negative-positive recruiting waves a slow negative wave developed. One of every two recruiting waves was often diminished when the preceding recruiting wave had reached considerable amplitude. The changes in the RR were antagonized by barbiturates and by caffeine. In conjunction with previous evidence these results support the hypothesis that spikes of spike-and-wave discharges in FGPE are generated by similar thalamocortical volleys as those creating RR and spindles. They further suggest that the crucial neuronal mechanism underlying this effect of penicillin is a shift in the emphasis from distal apical dendritic thalamocortical synapses on cortical pyramidal neurons to more proximal ones.
D000200:Action Potentials; D000818:Animals; D001921:Brain / Q000502:physiology*; D002415:Cats; D002540:Cerebral Cortex / Q000502:physiology; D004569:Electroencephalography; D010406:Penicillins; D012640:Seizures / Q000503:physiopathology*
D010406:Penicillins