Vasoactive intestinal polypeptide facilitates muscarinic transmission in mammalian sympathetic ganglia.

Vasoactive intestinal polypeptide (VIP) in the concentration of 1 microM or less markedly and selectively increased the amplitude and duration of the muscarinic slow excitatory postsynaptic potential (EPSP) without appreciably affecting the nicotinic fast EPSP or the non-cholinergic EPSP of guinea pig inferior mesenteric ganglion cells. The membrane depolarization evoked by the muscarinic agonist, acetyl-beta-methylcholine in these neurons was similarly enhanced by VIP. Our results suggest that the peptide may be a neuromodulator effective in enhancing the sensitivity of postsynaptic muscarinic receptors to acetylcholine in the vertebrate sympathetic ganglia.