Normal mechanicalactivityof catcolonicmusclesegments was abolished during incubation incalcium-freesolution. Incalcium-freesolution, contractions could be induced by direct electrical stimulation or by depolarization with high potassium. In high potassiumcalcium-freesolution, carbachol also induced an additionalcontractileresponse due to muscarinicreceptoroccupation. It is concluded that incolonicsmooth muscle, depolarizationmediated, as well asreceptormediated, release of intracellularcalciumoccurs.
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