The role of cAMP-dependent pathway. The CNS-EC were pretreated for 30 minutes with 0.5 μmol/L of the specific PK-A inhibitor, H-89, or with 300 μmol/L of PK-A–activating cAMP analog dBu-cAMP, followed by 1 hour of incubation with 100 nmol/L Et-1. The autoradiographic (A) and graphic data (B) are presented as described in Fig 2.