Release of a bradykinin-like substance of nervous stimulation of a frog stomach muscle preparation.

Abstract

Acetylsalicylic acid antagonises the action of certain polypeptides in some tissues, but has no effect on similar action of other polypeptides (COLLIER, 1963). Vagal stimulation of frog stomach muscle releases substance P or neurokinin (SINGH, 1964), but the resulting contraction may either be abolished by acetylsalicylic acid (SINGH, 1965), or may be resistant to it (SINGH and SINGH, 1966). This suggests that vagal stimulation releases two polypeptides. In the present research an attempt has been made to determine whether any other polypeptide is released by the vagus nerve, besides substance P or neurokinin. Methods The stomach of the frog, Rana tigrina, was dissected out with a vagus nerve attached. It was split by cutting along the greater curvature and the mucous membrane gently removed. The muscle layers were then washed for 30 min in Tyrode or De Jalon solution to remove any extraneous substances. Since frog stomach muscle responds well to stimulation in Tyrode or De Jalon solution, the solution can be added without further modification to a test organ bath containing guinea pig ileum, rabbit small intestine or rat duodenum. After the preliminary wash the stomach muscle was laid for 1 hr in a tilted Petri dish containing 15 ml of Tyrode or De Jalon solution to study spontaneous release of polypeptides. Thereafter the vagus nerve was stimulated by rectangular pulses of