Postsynaptic effects of 4-aminopyridine in the sixth abdominal ganglion of the cockroach.

The synaptic action of 4-aminopyridine (4-AP) was studied in the sixth abdominal ganglion of the cockroach Periplaneta americana L. The drug 4-AP did not modify the affinity of cholinergic receptors. At concentrations above 10(-4)M, 4-AP depolarized the postsynaptic membranes even after blockage of muscarinic and nicotinic receptors by antagonistic substances.