The salivary secretion from the cat submandibular salivary gland induced by parasympathetic nerve stimulation is considered to be due to release of acetylcholine (ACh) which binds to muscarinic receptors and activates secretory elements¹. Recent evidence suggests that cholinergic neurones in the cat submandibular gland contain and release another neurotransmitter candidate, vasoactive intestinal polypeptide (VIP)^2,3. Although VIP per se does not induce salivary secretion, it potentiates the secretion induced by ACh infusions^2,3. The present study offers a possible explanation for this potentiation by showing that VIP in physiologically relevant concentrations enhances the binding of muscarinic cholinergic ligands in the cat submandibular gland.