ABSTRACT
Cholinergic antagonists are now widely used in the treatment of obstructive airways diseases and may be the bronchodilators of choice in the treatment of COPD, where cholinergic tone is the only reversible component. The recognition that there are multiple subtypes of muscarinic receptor in lung has raised important questions about their role in regulation of airway function, and creates the prospect of more selective therapy in the future (1). Five distinct human muscarinic receptor genes have so far been identified (2), and four subtypes of muscarinic receptor (M1 to M4) have now been recognized in lung both pharmacologically and using specific cDNA probes (3-7) (Fig. 1). These subtypes of muscarinic receptor subserve different physiological roles in the airways, but their clinical relevance in the treatment of airway disease is not yet certain.
