ABSTRACT
The effect of nivalin-P (nivalin:pymadin/4-aminopiridine hydrochloride ratio--1:1) on the smooth muscles of the gastro-intestinal tract was studied. The experiments were carried out on guinea-pig ileum, rabbit jejunum using the method of Magnus, and on isolated strips of guinea-pig stomach and taenia coli by the modified method of Golenhofen. The agents studied were added to the incubation medium in the following concentrations: acetylcholine--1 X 10(-7) g/ml to 2 X 10(-6) g/ml, pymadin--up to 2 X 10(-6) g/ml, nivalin--up to 2 X 10(-6) g/ml, nivalin-P--up to 2 X 10(-6) g/ml, pancuronium, diadonii and galamine--from 2 X 10(-5) to 4 X 10(-4) g/ml, isoptin--from 1 X 10(-5) to 2 X 10(-5) g/ml and sodium nitroprusside--2 X 10(-5) to 4 X 10(-5) g/ml. Nivalin was found to increase mainly the tone of the smooth muscles, while pymadin increases predominantly the amplitude of the contractions. The combined agent nivalin-P stimulates both the phasical and the tonic activity. The role played by calcium ions in the mechanisms of the stimulating effect of nivalin-P on the smooth muscles is discussed.
