Cyclic AMP facilitates the electrically evoked release of radiolabelled noradrenaline, dopamine and 5-hydroxytryptamine from rat brain slices.

The adenylate cyclase activator forskolin as well as 8-bromo-cyclic AMP enhanced the electrically evoked release of 3H-noradrenaline and 3H-5-hydroxytryptamine from superfused rat neocortical slices and that of 3H-dopamine from neostriatal slices with comparable EC50's of about 0.5 and 50 microM, respectively, without affecting spontaneous tritium efflux. The phosphodiesterase inhibitor ZK 62771 (3-100 microM) also enhanced 3H-noradrenaline and 3H-dopamine release but slightly reduced 3H-5-hydroxytryptamine release. However, this drug profoundly enhanced spontaneous tritium release in the latter case. The facilitatory effect of forskolin (0.3 microM) on the release of the amine neurotransmitters was potentiated in the presence of ZK 62771 (30 microM). Therefore, cyclic AMP appears to exert a general facilitatory effect on the release of these biogenic amines from central nerve terminals.