Pharmacological Properties of Kryptopyrrole and Its Oxidation Products on Isolated Sciatic Nerve of Rat and on Guinea‐pig Ileum

Abstract

1Kryptopyrrole (2, 4-dimethyl, 3-ethylpyrrole) inhibited conduction in rat sciatic nerve by a local anaesthetic action. 2 Tone and both spontaneous and electrically-induced contractions of guinea-pig ileum were also inhibited by kryptopyrrole. The concentration of kryptopyrrole required for 50% inhibition of a maximum twitch tension (ID50) was 0.085 mm.3 Oxidation products of kryptopyrrole with chromatographic properties similar to those of urinary constituents reported in schizophrenia and hepatic porphyrias had little or no effect at similar concentrations. 4 Dose-response curves to exogenous acetylcholine in guinea-pig ileum were shifted to the right by kryptopyrrole, with loss of parallelism and reduction in the maximum contraction. 5 Acetylcholine overflow from ileal segments at rest and during electrical stimulation was reduced by kryptopyrrole. 6 These results on ileal segments are consistent with kryptopyrrole having both a post-junctional site of action, presumably directly on the muscle, and a pre-junctional site reducing the output of acetylcholine from the myenteric plexus. 7 The significance of these findings is discussed in relation to a possible clinical pathological role for these compounds.