The action of aminopyridine on the electromotor synapse of Torpedo marmorata

An investigation of the action of 4-aminopyridine (4-AP) on Torpedo electromotor synapses was performed using the microelectrode technique. 4-AP in concentrations of 1--10 micrometers increased the peak amplitude (p) and half-decay time (t 1/2) of the intracellularly recorded excitatory postsynaptic potentials (EEP), independent of alterations in miniature EPPs or membrane potential. 4-AP also increased the amplitude and time constant of decay (tau) of the excitatory postsynaptic current (EPC). Analysis of the results supports potentiated transmitter release and accumulation of the transmitter in the synaptic cleft as the mechanism by which 4-AP produces its effect.