 This way, a positive inotropic effect elicited by EHNA, as a result of PDE2 inhibition, was observed.BAY 60-7550 is an analog of EHNA, which is more than 100-fold more potent and is highly selective for PDE2A.Other newly discovered selective PDE2 inhibitors are PDP (9-(6-phenyl-2-oxohex-3-yl)-2-(3,4-dimethoxybenzyl)-purin-6-one)  and oxindole.