Xerostomia is the symptom of dry mouth often seen in patients who receive head and neck
radiation therapy or in patients who have Sjögren's syndrome. The primary treatment to relieve
xerostomia symptom is
oral administration of
pilocarpine, a parasympathomimetic agent with
muscarinic action. Increase in salivary secretion induced by systemic administration of
pilocarpine is considered to be mediated by actions on
muscarinic cholinergic receptors in the central nervous system and salivary glands. In this study, we investigated the direct effect of
pilocarpine on salivary fluid secretion in the isolated, perfused rat submandibular gland.
Pilocarpine provoked salivary fluid secretion in a dose-dependent manner. The Na(+)-channel blocker
tetrodotoxin had almost no effect on the
pilocarpine-induced salivary fluid secretion, indicating that
pilocarpine directly stimulates submandibular gland.
Pilocarpine induced an increase in intracellular Ca(2+) concentration in dispersed submandibular gland cells at 37 degrees C, but not 25 degrees C. The salivary fluid secretion induced by
pilocarpine was consisted of a rapid and transient phase and a subsequent sustained phase, which profile was different from that evoked by
carbachol, another typical
muscarinic agonist.
Pilocarpine also induced
Lucifer yellow secretion via paracellular route.