EFFECTS OF DEXMEDETOMIDINE ON CONTRACTILITY, RELAXATION, AND INTRACELLULAR CALCIUM TRANSIENTS OF ISOLATED VENTRICULAR MYOCARDIUM

The effects of the highly selective alpha2-adrenoceptor agonist dexmedetomidine on contractility, relaxation, and the intracellular Ca2+ transients of isolated ventricular myocardium were studied in isolated right ventricular papillary muscles obtained from reserpinized ferrets. Dexmedetomidine (10-10-10-5 M) did not alter amplitude and time variables of isometric, isotonic and zero-load-clamped twitches, except for a slight increase in maximal isotonic relaxation rate at 10-5 M. Dexmedetomidine (10-8-10-5 M) caused no changes in the intracellular Ca2+ transient detected with aequorin. These results suggest that dexmedetomidine has no intrinsic myocardial contractile effects.