Frequency dependent inhibition of the nicotinic transmission by serotonin in vesical pelvic ganglia of the rabbit.

Intracellular recordings were made from neurons in rabbit vesical pelvic ganglia (VPG), in vitro. Increasing the frequency of preganglionic-nerve stimulations from 0.1-1 Hz to 10-20 Hz facilitated fast excitatory postsynaptic potentials (EPSPs), resulting in a generation of action potentials. Acetylcholine-induced response was not altered during the facilitation of the fast EPSP. Serotonin blocked action potentials elicited by preganglionic-nerve stimulations at 0.1 Hz, while it caused no blockade at 10 Hz. Serotonin may potentiate the feature of high-pass filter in transmission of VPG. Immunohistochemical study demonstrated serotonin-like varicose terminals in rabbit VPG.