The M1 receptor is a protein found in the brain and is heavily implicated in memory and cognition. Drugs targeted at this protein can also cause diarrhoea, but the precise mechanism of this gastrointestinal effect is unknown. This thesis aimed to understand how the M1 receptor affects gastrointestinal function by using compounds that specifically activate the receptor. Results presented in this thesis demonstrate that activating the M1 receptor stimulates colonic contractions that may promote the defecation process.