3,4-diaminopyridine-evoked Noradrenaline Release in Hippocampal Slices: Further Properties and Involvement of Adenylate Cyclase

Noradrenaline (NA) release evoked in rabbit hippocampal slices by 200 μM 3,4-diaminopyridine (DAP) is only partly dependent on extracellular Ca 2+ , which appears to enter the nerve endings via omega-conotoxin-sensitive N-channels. Since forskolin, 8-bromo-cAMP and phosphodiesterase inhibitors, but also phorbol esters markedly enhanced the DAP-evoked NA release, both adenylate cyclase and protein kinase C appear to take part in the mechanism of this release. The inhibitory effect of the α 2 -adrenoceptor agonist clonidine was reduced in the presence of forskolin, indicating an (at least functional) interaction of α 2 -adrenoceptor signal transduction with adenylate cyclase activation.