Actions of vasoactive intestinal polypeptide in superior cervical ganglion of the cat

Effects of vasoactive intestinal polypeptide (VIP) in the superior cervical ganglion (SCG) of the cat were investigated in situ. Vasoactive intestinal polypeptide (0.075-1.5 nmol) induced a dose-dependent depolarization of the superior cervical ganglion, characterized by a long-latency, slow onset, small amplitude and long duration. Initial short-lasting hyperpolarization of the superior cervical ganglion was observed in 5 out of 8 experiments after administration of VIP in a dose of 0.75 nmol. Vasoactive intestinal polypeptide (0.075-1.5 nmol) unmasked the muscarinic slow negative potential, following the compound action potential and unmasked or enhanced the stimulus-bound decremental oscillatory potentials induced by the muscarinic agonist McN-A-343 in the superior cervical ganglion. Vasoactive intestinal peptide induced a slight, but significant increase in the amplitude of the postganglionic action potentials evoked by preganglionic stimulation. The data mentioned above suggest that VIP may act as a neuromodulator of cholinergic transmission at the ganglionic synapse.