Effects of the PDE2 inhibitors Bay 60-7550 (BAY; a) and ND7001 (b), alone and in combination with NO modulators, on cGMP in neuronal cultures. Values are expressed as means ± S.E. (n = 3–4). **, p < 0.01 compared with control; #, p < 0.05 compared with Bay 60-7550; $, p < 0.05 compared with detanonoate (DETA).