Abstract-Effects of diltiazem were investigated on the isolated portal vein of the guinea pig in hypertonic solution. Hyperosmolarity was produced by sucrose.
Abstract-Effectsof trimebutine maleate (TM-906) on the spontaneous contraction of isolated guinea pig colon were investigated.TM-906 in the concentrations of 10-6 g/ml and 10-5 g/ml increased the tone without affecting the amplitude of the spontaneous contraction in the preparations with low tone, whereas it decreased the tone and the amplitude of the spontaneous contraction in the preparations with high tone. At the higher concentration (10-4 g/ml), TM-906 decreased the tone and finally abolished the spontaneous contraction in any preparation. The increase in tone induced by TM-906 was prevented by diltiazem and exposure to Ca'-free solution, but not by tetrodotoxin, atropine, phentolamine or propranolol, and depended on the extracellular concentration of CaCI2. On the other hand, the decrease in tone and amplitude of the spontaneous contraction produced by TM 906 were not prevented by tetrodotoxin, phentolamine or propranolol. TM-906 further increased the tone increased by 10 mM KCI, while it decreased the tone increased by 30 mM KCI. From results described above, it is suggested that TM 906 possesses both a relaxing effect and an excitatory effect which seem to be due to its direct action on the smooth muscle.
Abstract-Effectsof trimebutine maleate (TM-906) on the spontaneous contraction of isolated duodenum and ileum were studied in both guinea pigs and rabbits. In the duodenum and ileum of both guinea pigs and rabbits, TM-906 (10-6 g/ml, 10-5 g/ml) produced a potentiation of the spontaneous contraction in preparations with low contractile activity (low tone or small contraction), while it caused an inhibition of the spontaneous contraction in preparations with high contractile activity (high tone or large contraction).The potentiation of spontaneous con traction by TM-906 was more pronounced in the ileum than in the duodenum of both guinea pigs and rabbits. When the spontaneous contraction of duodenum and ileum was decreased by atropine, the potentiation of spontaneous contraction by TM-906 was further augmented and was more pronounced in the ileum than in the duodenum.When the spontaneous contraction was remarkably poten tiated by physostigmine or acetylcholine, TM-906 markedly inhibited the poten tiated spontaneous contraction, and the potentiation by TM-906 seen in pre parations with low contractile activity disappeared. From these results, it is concluded that TM-906 produces, depending on the contractile activity of the preparations, a potentiation or an inhibition of the spontaneous contraction of duodenum and ileum in both guinea pigs and rabbits and that the potentiation by TM-906 is more pronounced in the ileum than in the duodenum. It is suggested that the endogeneous acetylcholine partly modifies the effects of TM-906, but that it does not relate to the more pronounced potentiation by TM-906 in the ileum than in the duodenum.
In isolated guinea pig taenia coil, it was demonstrated by means of the double sucrose gap method that diltiazem (1), a potent coronary vasodilator (2), causes a decrease in the contractile force, with or without changes in the spike activity (3). The spike activity measured by the sucrose-gap method is, however, the sum and synchronized discharge of the spikes of a number of cells. For more detailed investigations of the electrophysiological effect of diltiazem on smooth muscle, intracellular recordings of the action potential front a single cell of the taenia coil were carried out.Guinea pigs (250-350 g) were stunned and bled. The taenia coli (approx. 15 mm in
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