INTRODUCTION In medical education&research are till today usual cardio-vascular preparations of frog, rat, rabbit, etc. An essential part of experiments with isolated angio-cardiac preparations could be replaced by fish organs. About pharmaco-physiological reactions of fish heart of salmo gairdner is reported [1,3]. Now is given information about ionic-dependent thermo-induced reactions: These demonstrate some common action mechanisms with mechanosensitive ionic channels of vesical (detrusor, trigone) myocytes [2]. METHOD Isolated heart and vascular strips from rainbow-trout (about 300g) from fish-shop are investigated about elementary physiological properties incl. motor actvity recording) & influence of physiological factors in Krebs-Henseleit-solution [1]. RESULTS Atrium&vantriculus carotis generate spontaneous contractions: [Ca++]-increase has positive, [K+] negative chrono- and inotropic effects. Negative acetylcholine and positive adrenaline effects (10nM-1µM) are antagonized by atropine&propranolol resp. (1µM). Ouabain (strophantine, 0.1-1µM) induce strong augmentation of cardiac contractions. Thermo-induced effects are strong dependent on ionic concentration. Change of some pharmaov-physiological factors (hormones, drugs) induce different rhythmic burst-like motor pattern at 14-24°C, contrary to regular&uniform motor activity at 6°C. CONCLUSION Fish cardiac preparations could reduce enormous application of animal organs in pharmacological industry and education&research at universities, i.e. this could laed to large animal protection. Table Thermo-induced reactions in trout atrium in dependence of CaCl2 and KCl At 24°C Atrium contraction frequency 67±23/min=100%, amplitudes 35±51 mm=100%, i.e. 4.7% of the prep.length of 0.6±1.3mm Isotonic recording, mean±standard deviation, p<0.05<0.01 A. CaCl2 2.1mmol/l=1x contr. ampl. in % of initial value (n=18) 24°C, 0.25x: 78±60, 1x: 213±118, 2x: 271±170 6°C, 0.25x: 24±16, 1x: 89±75, 2x: 156±152 contr. freq./min in % of initial value 24°C, 0.25x: 106±62, 1x: 87±47, 2x: 52±35 6°C, 0.25x: 28±15, 1x: 35±16, 2x: 31±14 B. KCl 4.6mmol/l=1x contr. ampl. in % of initial value (n=18) 24°C, 0.25x: 149±70, 1x: 113±65, 2x: 43±24 6°C, 0.25x: 118±120, 1x: 69±61, 2x: 3±6 contr. freq./min in % of initial value 24°C, 0.25x: 106±60, 1x: 97±93, 2x: 71±73 6°C, 0.25x: 34±14, 1x: 24±13, 2x: 2±4