Effects of eleven muscarinic drugs on trachea and ileum of guinea pig in vitro

The effects of eleven muscarinic subtype selective agonists and antagonists were observed on isolated trachea and lieum of guinea pig. The pAz values (against CCh) of 4-DAMP and AF-DX 116, both being putative M2 antagonists, were 9.04 and 5.9 on the ileum, and 6.94 and 6.70 on the trachea, respectively. The pAz values (against CCh) of gallamine, a neuromuscular blocker, were 5.40 and <3 on the trachea and ileum, respectively. The pAz values (against CCh) of pirenzepine, a putative M1 antagonist, on the ileum and trachea were similar, being around 6.80. These results suggest that the muscarinic receptors of trachea and ileum may not be homogeneous.