4-beta-phorbol-12,13-dibutyrate enhances K+-stimulated dopamine release from hippocampal slices.

Slices of rat hippocampus were labelled with [14C]dopamine, superfused continuously with oxygenated Krebs-Henseleit solution and stimulated with a potassium pulse (48 mM K+, 5 min.). 4-beta-phorbol-12,13-dibutyrate (PDB), an activator of protein kinase C (PKC), enhanced the potassium-evoked overflow of 14C. This effect was blocked by prior application of polymyxin B, a relatively selective inhibitor of PKC. In contrast, the PKC-inactive 4-alpha-phorbol-12,13-didecanoate (PDD) had no influence on the evoked transmitter overflow. The results suggest that PKC may also be involved in the regulation of hippocampal DA release. A possible link between PKC activation and DA release to processes of synaptic long-term potentiation is discussed.