CHRM4 is found mainly in the brain and CNS where it plays a central role in regulating dopamine signaling and release in the basal ganglia (Moehle & Conn 2019). It is also found in the intestine and the eye, as well as many other tissues. CHRM4 act via a Gi signalling pathway, which causes a decrease in intracellular cAMP leading to inhibitory-type effects (Caulfield & Birdsall 1998). Dicyclomine, is a medication that is used to treat intestinal spasms in conditions such as irritable bowel syndrome. Oxyphenonium is an antimuscarinic drug used to treat gastric and duodenal ulcers and to relieve visceral spasms. Tropicamide is an antimuscarinic drug that produces short acting mydriasis (dilation of the pupil) and cycloplegia (paralysis of the ciliary muscles of the eye) when applied as eye drops to allow better examination of the eye.