Long-lasting antagonistic effects of monatepil on Ca2+ current in guinea-pig ventricular cells.

Monatepil maleate (CAS 103377-41-9, AJ-2615), a new derivative of dihydrodibenzothiepins, showed dose-dependent inhibition of Ca2+ current (ICa) in single cardiac cells isolated from guinea-pig ventricle. ICa was elicited by depolarization from -40 mV to +10 mV at 0.2 Hz. IC50 value of monatepil for the peak ICa at +10 mV was 18.7 nmol/l. The ICa inhibition was still sustained 30 min after washout, indicating that monatepil had long lasting activity in the mammalian single muscle cell.