| Abstract: | A role of substance P in post-tetanic potentiation in the myenteric plexus-longitudinal muscle preparation of the guinea-pig ileum was investigated by means of substance P-antagonist, (D-Pro2, D-Trp7,9)-substance P. After the addition of substance P-antagonist (10(-7)-10(-5) mol x l-1) a dose-dependent reduction of post-tetanic potentiation of neurogenic twitches was observed. Post-tetanic potentiation was actually abolished in the presence of 10(-5) mol x l-1 substance P-antagonist. It has been shown previously by our group that post-tetanic potentiation is reduced in preparations desensitized by substance P; this, together with our present results supported the hypothesis that the release of substance P-like compounds during tetanic stimulation played a key role in the mechanism of post-tetanic potentiation. |
