Quantitative studies of spike foci induced by minimal concentrations of penicillin

The minimal concentrations of penicillin which induce stable recurrent spikes (20,000 U/ml) and which elicit stable recurrent after-discharges (100,000 U/ml) were determined. A quantitative study of the inter-relationships, variability and changes with time of a number of spike parameters (spike latency, spike amplitude, amplitude of prepositivity, spike duration and spike frequency) was performed. The study adds new information on the pathogenesis of the experimental spike focus and serves as baseline for quantitative evaluation of the effects of anticonvulsants on the characteristics of the primary spike focus and on after-discharges.