The β3 -adrenoceptor agonist mirabegron increases human atrial force through β1 -adrenoceptors: an indirect mechanism?

Mirabegron increases human atrial force through β1 - but not β3 -adrenoceptors. Desipramine and phenoxybenzamine block neuronal uptake and conceivably prevent mirabegron from releasing noradrenaline. A non-specific cardiodepressant effect is not mediated through β3 (or β2 )-adrenoceptors, consistent with lack of β3 -adrenoceptor function on human atrial contractility.