 It has been demonstrated to specifically act on PDE2 by inhibiting cGMP-activation of PDE2 with an IC50 value of ~1μM and an at least 50-fold selectivity over other PDEs.The core structure of EHNA resembles cAMP but differentiates in the fact that EHNA has a bulky hydrophobic carbon side chain replacing the phospho-ribose moiety in cAMP.In primary cultures of rat cortical neurons, the inhibition of PDE2A by EHNA potentiates NMDA ("N"-methyl-D-aspartate) receptor activated increase in cGMP, but has no effect on cAMP concentrations.