Relative potency of cholinomimetic drugs on the bovine iris sphincter strips.

On the isolated bovine iris sphincter strips, the dose-response curves to several cholinomimetic agents were obtained. When compared at EDS0 the relative potency appears as carbamylcholine 1, furtrethonium 1/5, pilocarpine 1/30, methacholine 1/40, acetylthiocholine 1/1500, acetylcholine 1/4800, and butyrylthiocholine 1/1400. The drugs which are substrate for acetylcholinesterase produce fat dose-response curves. Cold storage of the tissue for 48 to 60 hours did not influence the pharmacologic effect. Thus all these cholinomimetic agents did not appear to produce the effect through the endogenous liberation of acetylcholine.