Modulation of Interval-Force Dependence of Rat Papillary Muscle at Acute and Course Exposure of Amiodarone

Change of interval-force dependence of rat papillary muscles at acute and course use of amiodarone was investigated. Methods: The experiments were performed on isolated papillary muscles of Wistar rats. The extrasystolic (0.2 1.5 s), postextrasystolic contractions and post-rest (4 60 s) reactions of rat left papillary muscles perfused Krebs-Henseleit solution with amiodarone (1 μM) and papillary muscles of rat treated amiodarone in dose 20 mg/kg/day for 14 days were investigated. Results: It has been found that both acute and course use of amiodarone decreases the amplitude of extrasystolic contraction. At the same time, only acute use of amiodarone leads to additional enhancement of potentialtion of contractile response at extrasystolic impulse and performance of post-rest test. Conclusion was made, that both acute and course use of amiodarone decreases excitability of cardiomyocytes but only at course use this antiarrythmic drug increases effective refractory period of myocardium. Acute exposure of amiodarone is accompanied with change of functional state of cardiomyocyte sarcoplasmatic reticulum.