Muscarinic receptor agonists and antagonists

Although four different subtypes of the muscarinic acetylcholine (ACh) receptor with functional correlates are known to exist (function for M5 is still unclear), all muscarinic agonists and antagonists in clinical practice only show very weak selectivity. Therefore, intensive investigations are in progress to develop subtype selective ligands. This review describes the first M1 agonists and antagonists of the presynaptic M2 receptor, which can be used in the treatment of Alzheimer’s disease (AD), and M3 antagonists, which will be useful in the treatment of urinary urge incontinence. In addition, muscarinic agonists were found to exhibit analgesic effects and M4 antagonists may be useful in the treatment of movement disorders. However, the latter two pharmacological findings will need more research work to become established in clinical trials.