Butyrylcholine iodide is primarily used in biochemical research as a substrate for studying the activity of cholinesterase enzymes, particularly butyrylcholinesterase. It helps in understanding enzyme kinetics, inhibition, and the role of these enzymes in various physiological and pathological processes. Additionally, it is utilized in the development of assays for detecting cholinesterase activity, which is crucial in toxicology studies, especially in assessing the effects of nerve agents and pesticides. Its application also extends to neuroscience research, where it aids in exploring cholinergic signaling and its implications in neurodegenerative diseases such as Alzheimer's.