Dependence of the Electrical and Contractile Activities of the Gastric Smooth Muscle on Ca Ions
In spite of the opinion of many authors that the excitation-contraction coupling in the smooth muscle is effected in a way similar to that characteristic of the striated muscle, recent data have shown that the smooth muscle has some peculiarities of the excitation-contraction coupling. Thus the smooth muscle contraction is not always connected with the appearance and the pattern of the action potentials. In the vascular smooth muscle Somlyo and Somlyo have observed contractions which are not connected with spike potentials. Such contractions we have recorded from parts of the digestive tract. Of interest in this respect are the smooth muscles making up the different regions of the stomach. Whereas from the smooth muscles of the antrum and the corpus of the stomach of cat[2,3] and man spontaneous rhythmic slow potentials, type plateau (we will call them plateau action potentials, PAP) are recorded, the smooth muscle of the stomach fundus is characterized by slow changes in the membrane potential connected with tonic contractios. The objective of the present investigation is the role of Ca2+ in the realization of the excitation-contraction coupling in the smooth muscles of the antrum and fundus of the cat stomach.
KeywordsSmooth Muscle Contractile Activity Phasic Contraction Nitroprusside Sodium Tonic Contraction
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