The disclosure provides methods, treatments and materials for enhancing the effect of an adenosine A2 receptor agonist in the treatment, mitigation or prophylaxis of a disease or condition characterized by inotropic and/or lusitropic dysfunction, and/or enhancing adenosine A2 receptor function in the treatment, mitigation or prophylaxis of a disease or condition characterized by impaired adenosine A2 receptor function, comprising administration of an effective amount of a PDE1 inhibitor to a patient in need thereof, for example a patient suffering from heart failure.