[Effects of 3,6-dimethamidodibenzopyriodonium citrate (I-65) on action potentials and contractions in guinea pig papillary muscles].
Synchronous recordings of action potentials and contractile force in isolated guinea pig papillary muscles administered 3,6-dimethamidodibenzopyriodonium citrate (I-65) 30 mumol/L showed excitation-contraction uncoupling, ie, the contractile force was markedly depressed although the Vmax and amplitudes of the action potentials were unaffected. At the same concentration, I-65 shortened the duration of the action potentials at 50% and 90% repolarization. However, I-65 at lower concentrations (1-10 mumol/L) decreased Vmax and the amplitude of the slow action potentials which were elicited by isoprenaline in papillary muscles were rendered partially depolarized by KCl 25 mmol/L Tyrode solution. These effects were partially reversed by elevation of the concentration of Ca2+ from 2.7 to 5.4 mmol/L. I-65 also suppressed the abnormal automaticity elicited by BaCl2 and DAD and triggered activity induced by ouabain. The results suggest that I-65 may be a calcium channel blocker.
Cui
Y
Y
Tan
Y H
YH
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009861:Onium Compounds / Q000494:pharmacology*; D010210:Papillary Muscles / Q000187:drug effects / Q000502:physiology
D002121:Calcium Channel Blockers; D009861:Onium Compounds; C056078:3,6-dimethylaminodibenzopyriodonium citrate