Pilocarpine is a cholinergic agonist, meaning that it binds to muscarinic receptors and stimulates them to initiate a range of physiological responses. One of the effects of pilocarpine is miosis, or constriction of the pupil of the eye. Pilocarpine acts as an agonist on muscarinic receptors located in the dilator muscle of the iris, stimulating it to contract so that the pupil narrows. This action of pilocarpine is used therapeutically in glaucoma to help reduce intraocular pressure, as the narrowing of the pupil decreases the amount of aqueous humour that drains out of the eye. Miosis induced by pilocarpine can also be used to diagnose conditions like Horner's syndrome, where the pupil fails to constrict. In addition to its use in ophthalmology, pilocarpine can also be used topically to treat dry mouth, a condition often seen in patients undergoing chemotherapy. By increasing the production of saliva (a reflex caused by the action of pilocarpine on salivary glands), it can help to relieve the symptoms of dry mouth.