The influence of pentobarbital upon a cortical epileptogenic focus in rats

Three subsequent doses of pentobarbital (5, 15, and 40 mg/kg) were applied intraperitoneally in acute experiments in rats with a cortical epileptogenic focus. Histograms of intervals between individual focal discharges were shifted towards longer intervals even after the smallest dose of pentobarbital; the prolongation of intervals was clearly visible after the third dose also in the EEG recording. Shape of primary as well as projected cortical focal discharges after pentobarbital resembled that seen after local application of GABA. Barbiturate spindles which were present after the first and second dose of pentobarbital were regularly triggered by focal discharges. The mechanism of this triggering was probably a thalamocortical one, because marked projected discharges were recorded from various thalamic nuclei from the very beginning of focal activity.