Used as a cholinergic agonist in research settings to study acetylcholine receptor activity. It mimics the action of acetylcholine, primarily at muscarinic receptors, making it valuable in neuropharmacological studies, particularly in examining smooth muscle contraction, glandular secretion, and parasympathetic nerve signaling. Often employed in in vitro experiments to stimulate muscarinic receptors. Its iodide salt form enhances solubility and stability in aqueous solutions, suitable for physiological preparations. The related chloride salt is used clinically for bronchial challenge testing to diagnose asthma, while the iodide form is preferred in research.