Affinity and efficacy correlate with chemical structure more than potency does in a series of pentatomic cyclic muscarinic agonists.

The efficacy and affinity of nine pentatomic cyclic muscarinic agonists were determined on the guinea-pig ileum, according to the method of Furchgott & Bursztyn (1967). The efficacy and affinity of these agonists are affected differently by structural modifications. Our results suggest that a strong dipole oriented in the same direction as that of the hydroxy group of muscarine, or the presence of a polarizable atom in the same position, are important for efficacy.