Effects of-(N, N-diethylamino) octyl-3,4,5-trimethoxy benzoate-hydrochloride (TMB-8) on skinned myocardial fibers of the rat

• Published in: Japanese Journal of Pharmacology 1996, Vol.71 (suppl.1), p.224-224
• Main Authors: Sumiko Takahashi, Mika Adachi, Hikaru Tanaka, Koki Shigenobu
• Format: Article
• Language: Japanese
• ISSN: 0021-5198

The effects of TMB-8, which is reported to inhibit the release of intracellularly stored calcium in skeletal and smooth muscles, were examined in ventricular myocardia of the adult rat. In skinned papillary muscle fibers with functional sarcoplasmic reticulum (SR) preserved, application of TMB-8 at concentrations up to 300 μM during the Ca^2+ loading period had no significant effect on the peak tension of subsequent caffeine-induced contraction, although its reduction was observed at a higher concentration (1000 μM). In contrast, when 100 to 1000 μM TMB-8 was applied during exposure to caffeine, concentration-dependent reduction of the peak tension was observed. TMB-8 had no substantial influence on the Ca^2+ -tension relation of skinned fibers without functional SR. In isolated papillary muscle preparations, TMB-8 produced prolongation of the action potential duration and decrease in Vmax leading to abolition of contraction at 100 μM. In conclusion, although it has additional effects on the action potential, TMB-8 would be a useful pharmacological tool to inhibit Ca^2+ release from SR in skinned myocardial preparations.