The influence of repeated systemic penicillin injections at subconvulsive doses on spontaneous spike-wave discharges...

Changes in nonconvulsive spontaneous epileptic activity-Spike-Wave Discharges (SWD)-induced by repeated intraperitoneal (i.p.) administration of crystalline penicillin (PC) at subconvulsive doses were evaluated in imp-DAK rats. Three groups received ten daily i.p. injections of PC at doses of 750,000, 500,000 and 250,000 IU/kg b.w. For comparison, another classic convulsant, pentylenetrazol (PTZ) was applied in the same way to another group. PTZ was also given to all rats before and after injection series for better evaluation of changes in CNS excitability. Repeated PC injections resulted in a progressive increase in the basal level of the spontaneous SWD activity and in an increase in the SWD response to PC, which was statistically significant in the case of the dose 750,000 IU/kg. Moreover, in all rats given PC the response to PTZ (increase in SWD activity) was reduced. The results obtained in this and previous experiment suggest that in the course of repeated systemic Pc administration adaptive changes in the rat CNS develop which prevent the convulsive effects of Pc but promote the occurrence of the spontaneous nonconvulsive SWD activity.