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Effects of amrinone on the transmembrane action potential of rabbit sinus node pacemaker cells
Author(s) -
Kodama Itsuo,
Kondo Noriaki,
Shibata Shoji
Publication year - 1983
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1983.tb10723.x
Subject(s) - amrinone , sinoatrial node , medicine , chemistry , verapamil , membrane potential , calcium , electrophysiology , endocrinology , biophysics , inotrope , heart rate , biology , biochemistry , blood pressure
1 Effects of amrinone on the membrane action potential and spontaneous activity were investigated in sinus node pacemaker cells of rabbit heart by use of microelectrode techniques. 2 Amrinone (1 × 10 −4 m to 6 × 10 6 m ) caused a shortening of cycle length of spontaneous firing (SPCL) accompanied by an increase in the maximum upstroke velocity at phase 0 () and amplitude of action potential (AAP), while it did not affect the maximum diastolic potential (MDP). 3 All the effects of amrinone on sinus node pacemaker cells were markedly attenuated or abolished in a low calcium medium (Ca + 0.1 m m or 0.3 m m ) or in the presence of the slow channel blocking agent, verapamil (5 × 10 −7 m , 2 × 10 6 m ). 4 The effects of amrinone were not antagonized by the β‐adrenoceptor blocking agent, pindolol (2 × 10 −7 m ). 5 These results indicate that amrinone has an intrinsic effect on sinus node pacemaker cells, increasing their spontaneous firing activity. 6 It is also assumed that the effects of amrinone on sinus node cells are probably mediated by an augmentation of the slow calcium and/or sodium inward current through the cell membrane.