Decrease of inhibitory driving force in crayfish stretch reception: a mechanism of the convulsant action of penicillin.

The effect of penicillin on the evoked IPSP was investigated in the isolated crayfish stretch receptor. The IPSP driving force (IPSP reversal potential minus membrane potential) was reduced in a dose-dependent fashion but, when necessary correction was made for the decrease in resting membrane conductance, the synaptic conductance was only slightly reduced. The possibility that a penicillin-induced intracellular acidification was responsible for the decrease in IPSP driving force is considered.