1. The effects of frequency of orthodromic and antidromic stimulation
of CA3 on formation of electrographic seizurelike discharges in CA1 wa
s studied in the high potassium hippocampal slice. 2. Within the range
of stimulation of CA3 used, 0.1-10.0 Hz, a narrow range was identifie
d between 1.0 and 1.3 Hz, where the tonic phase of seizure generation
in CA1 was suppressed. This suppression was observed for both Schaffer
collateral and messy fiber stimulation.