[Effects of the membrane potential level on serotonin-induced contraction of the pulmonary artery smooth muscle in rabbits].

The effects of changes in membrane potential level on the electrical and contractile responses induced by serotonin (10(-6) mol/l) were investigated in muscle strips from rabbit main pulmonary artery using sucrose-gap technique. In spite of the fact that serotonin-induced depolarization did not exceed the threshold level for development of contraction, it was followed by a strong tonic contraction. Nearly a half of this contraction could be relaxed by an electrotonic hyperpolarization of the membrane.

[Effect of estradiol in uterine tissue with disturbed innervation].

Desympathization of the uterus in albino rats increased the intensity of 3H-estradiol inclusion into its tissues, while division of the parasympathetic nerves on the contrary, reduced it. Both types of denervation prevent increase of the cAMP and cGMP content in the organ under the effect of estradiol. Thus, the neural influences and the effect of estradiol in the uterine tissues are related.

[Mechanism of the effect of dibasol on the contractile and electric activities of the smooth muscle of the portal vein].

The effects of dibasol on spontaneous electrical and contractile activities as well as on the reactions evoked by hyperkalemic solution and noradrenaline were studied in smooth muscle of rabbit portal vein. It was shown that dibasol blocked the potential-operated influx Ca2+ into smooth muscle cells. The noninactivating calcium channels were found to be more sensitive to dibasol than inactivating ones.

[Excitation-contraction coupling in the smooth muscle of the femoral artery under the effects of noradrenaline].

Noradrenaline (5 x 10(-8) - 10(-5) M) induced a dose-dependent contraction of muscle strips from rabbit femoral artery. At concentrations higher than 10(-7) M noradrenaline evoked also a depolarization of smooth muscle cells due to an increase in sodium and/or chloride permeability of the membrane. Repolarization of the membrane to original level by inwardly applied current resulted in restoration of membrane resistance and partial relaxation of noradrenaline-evoked contraction.

[The role of calcium and potassium conductance in electrogenesis of smooth-muscle cells of the basilar artery].

The role of calcium and potassium conductances in electrogenesis of smooth muscle cells of the bovine basilar artery has been investigated using blocking agents of calcium and potassium channels both in the normal Krebs solution and in hyperpotassium solution under anelectrotonic repolarization of the cell membrane. It is shown that both voltage-operated calcium and potassium conductances participate in generation of gradual action potentials evoked by electrical stimulation. A higher contribution of potassium conductance into the total membrane conductance during depolarization is found to be the main factor interfered with development of full-size action potential.