Cholinergic enhancement of penicillin-induced epileptiform discharges in pyramidal neurons of the guinea pig hippocampus.

Acetylcholine (1-20 mM) was applied to guinea pig hippocampal slices bathed in normal and penicillin-containing media. Recordings in the CA 1 pyramidal cell layer in the presence of penicillin showed that acetylcholine caused a prolonged enhancement of the extracellular field potential. Intracellular recordings documented an increase in duration of cell bursting, a decrease in burst afterhyperpolarization, and a membrane depolarization lasting 1-5 min. These results suggest that the actions of acetylcholine to increase membrane excitability interact with penicillin-induced disinhibition to enhance hippocampal epileptogenesis.