THE INFLUENCE OF REPEATED SYSTEMIC PENICILLIN INJECTIONS AT SUBCONVULSIVE DOSES ON SPONTANEOUS SPIKE-WAVE DISCHARGES IN THE RAT

Changes in nonconvulsive spontaneous epileptic activity Spike-Wave Dis charges (SWD) - induced by repeated intraperitoneal (i.p.) administrat ion of crystalline penicillin (PC) at subconvulsive doses were evaluat ed 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 excitab ility. Repeated PC injections resulted in a progressive increase in th e basal level of the spontaneous SWD activity and in an increase in th e 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 i n this and previous experiment suggest that in the course of repeated systemic Pc administration adaptive changes in the rat CNS develop whi ch prevent the convulsive effects of Pc but promote the occurrence of the spontaneous nonconvulsive SWD activity.