eng Oriental Scientific Publishing Company Biomedical and Pharmacology Journal 0974-6242 2025-09-30 18 3 2463 2473 10.13005/bpj/3270 67727 article Qurbonova Shakhnoza Bakhtiyorovna 1 Zhumaev Inoyat Zulfiqorovich 1 Boboev Sadriddin Nurillo Ugli 1 Usmanov Pulat Bekmuratovich 1 Rustamov Shavkat Yusubovich 1 Zaripov Abdisalim Abdikarimovich 1 Department of Cell Biophysics, Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan Department of Alkaloids Chemistry, Institute of Chemistry of Plant Substances, Academy Sciences of Uzbekistan, Tashkent, Uzbekistan During the study, the inotropic and antiarrhythmic properties of the alkaloid 1-(3ˊ-Bromophenyl)-6,7-methylenedioxy-1,2,3,4-tetrahydroisoquinoline hydrochloride (F-25) were investigated. The alkaloid F-25 was shown to exert a negative inotropic effect on the contractile force of rat cardiac papillary muscle, decreasing myocardial contractility by 87.6±4.2% at a concentration of 100 μM compared to the control. To assess the involvement of voltage-gated Na⁺ channels in providing the negative inotropic effect of the alkaloid F-25, experiments were conducted using lidocaine, a specific blocker of this channel. When the effect of F-25 alkaloid (100 μM) was tested in the existence of lidocaine (IC₅₀=15.4 μM), the amplitude of papillary muscle contraction force was 32.8±3.9%, respectively. The influence of the alkaloid F-25 on Na⁺/Ca²⁺ exchange was examined using NiCl₂, a non-specific blocker of this exchanger. The negative inotropic effect of the alkaloid F-25 (100 μM) on papillary muscle contraction activity in the presence of a 10 mM concentration of NiCl₂ in the incubation medium was 42.3±4.2%. The negative inotropic effect of the alkaloid F-25 is exerted mainly by modulating the function of Na⁺ channels and, in part, the Na⁺/Ca²⁺ exchange. The impact of the alkaloid F-25 was also evaluated using an aconitine-induced arrhythmia model, revealing that the compound exhibits strong antiarrhythmic properties https://biomedpharmajournal.org/vol18no3/antiarrhythmic-effect-of-1-3-bromophenyl-67-methylenedioxy-1234-tetrahydroisoquinoline-hydrochloride/ Antiarrhythmic action Isoquinoline alkaloid Na⁺/Ca²⁺-exchanger Na⁺-channel Papillary muscle