[Maintenance of the contraction time of the smooth muscle cell]

It has been analyzed the speed of contraction (measured as Vmax) of guinea-pig intestine in vitro, after stimulation with carbachol. High doses of carbachol induce an high Vmax; but repeating the dose at short interval (4 min) the speed of contraction is reduced until it reaches values of Vmax 4,3. Low doses of carbachol determine a low Vmax that with repeating doses increases until Vmax 4,2. On the base of this tendency at the same Vmax, and from the anomalous behaviour of the intestines to one dose in front to different doses in carbachol. The excludes that the process could be due to a passive adaptation and hypothesizes a model of behaviour inside the cell. A model to which the myocells balance the stimulus in the way to make constant their velocity of contraction.