Pilocarpine induces the residual secretion of salivary fluid in perfused submandibular glands of rats

Pilocarpine is an M3 muscarinic agonist that is widely used for the treatment of xerostomia caused by various diseases and medical conditions. Pilocarpine induced the secretion of salivary fluid in perfused submandibular glands of rats. The secretion of salivary fluid observed after removal of pilocarpine was referred to as residual fluid secretion. The volume of fluid and time of the residual secretion depended on the dose of pilocarpine. Such a residual effect of pilocarpine was observed on fluid secretion via the paracellular pathway and oxygen consumption. When a muscarinic antagonist was added to the perfusate immediately after cessation of pilocarpine, residual secretion of salivary fluid did not occur. These observations indicate that the residual secretion of salivary fluid is a characteristics of the interaction of pilocarpine with muscarinic receptors.