eng Oriental Scientific Publishing Company Biomedical and Pharmacology Journal 0974-6242 2022-12-20 15 4 2309 2316 10.13005/bpj/2569 47001 article Inoyat Z. Zhumaev 1 Sadriddin N. Boboev 1 Pulat B. Usmanov 1 Shakhnoza B. Qurbonova 3 Shavkat Yu. Rustamov 1 Adilbay T. Esimbetov 1 Institute of Biophysics and Biochemistry of National University of Uzbekistan, Institute of the Chemistry of Plant Substances, Uzbek Academy of Sciences, Tashkent, 3Tashkent state pedagogical university named after Nizami, Uzbekistan. In the present study, the dose-dependent effect of the alkaloid vincanine on the contractile activity of rat heart papillary muscle was investigated and it was found to increase the force of muscle contraction at all concentrations. The half-maximal inotropic effect concentration (ED₅₀) of vincanine was 21.8 μM, respectively. Studies of the effect of this alkaloid on the cardiomyocyte Na⁺-channel in the presence of its blocker lidocaine showed that the positive inotropic effect of vincanine does not involve the Na⁺-channel. When studying the effect of vincanine on Сa²⁺_L-channels in the presence of nifedipine (IC₅₀=0.01 μM), the positive inotropic effect of vincanine (50 μM) alkaloid was partially reduced. In general, it was found that the positive inotropic effect of vincanine on the force of papillary muscle contraction is partially mediated by Сa²⁺_L-channels and mainly Na⁺/Сa²⁺ exchange. https://biomedpharmajournal.org/vol15no4/mechanism-of-positive-inotropic-effect-of-vincanine-on-cardiac-muscle-contraction-activity/ Cardiac Muscle  Inotropic Activity Ion-Channels  Indole Alkaloid