In vitro activity: Pilocarpine is a parasympathomimetic alkaloid obtained from the leaves of tropical American shrubs from the genus Pilocarpus. It is a non-selective muscarinic receptor agonist in the parasympathetic nervous system, which acts therapeutically at themuscarinic acetylcholine receptor M3 due to its topical application, e.g., in glaucoma and xerostomia. Pilocarpine acts on a subtype of muscarinic receptor (M3) found on the iris sphincter muscle, causing the muscle to contract and engage in miosis. Pilocarpine also acts on the ciliary muscle and causes it to contract. When the ciliary muscle contracts, it opens the trabecular meshwork through increased tension on the scleral spur. This action facilitates the rate that aqueous humorleaves the eye to decrease intraocular pressure. In ophthalmology, pilocarpine is also used to reduce the possibility of glare at night from lights when the patient has undergone implantation of phakic intraocular lenses; the use of pilocarpine would reduce the size of the pupils, relieving these symptoms. The most common concentration for this use is pilocarpine 1%, the weakest concentration. Pilocarpine is also used to treat dry mouth (xerostomia) which can occur, for example, as a side effect of radiation therapy for head and neck cancers. Pilocarpine stimulates the secretion of large amounts of saliva and sweat.

Cell Assay: Cell viability is determined by MTT assay. Briefly, HCS cells are inoculated into a 96-well culture plate (Nunc) at a density of 1×104 cells/100 µL/well, and are cultured and treated. At a 4h interval, the Pilocarpine (0.625 to 20 g/L)-containing medium is replaced entirely with 100 µL serum-free DMEM/F12 medium containing 1.0 g/L MTT, and the cells are incubated at 37°C in the dark for 4h. After the MTT-containing medium is discarded with caution, 150 µL DMSO is added to dissolve the produced formazan crystals at 37°C in the dark for 15 min, and the absorbance at 490 nm is measured with a Multiskan GO microplate reader