Chronotropic and inotropic actions of amrinone, carbazeran and isobutylmethyl xanthine: role of phosphodiesterase inhibition

1. The chronotropic and inotropic effects of amrinone, carbazeran and 3-isobutyl-1-methyl xanthine (IBMX) were examined in isolated preparations of papillary muscle and right atria from rabbit heart. The effects of the drugs on cardiac phosphodiesterase and cyclic nucleotide content were also examined. 2. Amrinone (2.4 x 10(-4)M-2 x 10(-3) M), carbazeran (9.1 x 10(-6) M-1.2 x 10(-3) M), and IBMX (1.8 x 10(-5) M-4.5 x 10(-4) M) produced …