PKC links Gq-coupled receptors to DAT-mediated dopamine release.

The dopamine transporter (DAT) mediates dopamine uptake in many brain areas and has been suggested to underlie dopamine release in the substantia nigra pars reticulata. This release modulates basal ganglia output and motor performance. It is triggered by glutamatergic subthalamic afferents. We show here that activation of (G(q)-coupled) group I metabotropic glutamate receptors are sufficient to induce dopamine release in rat substantia nigra pars reticulata slices. Release was measured by amperometry and inhibited by a DAT antagonist. In a DAT-expressing cell line, dopamine release could be induced by activation of G(q)-coupled muscarinic receptors. Release was measured by HPLC and inhibited by a DAT antagonist. In both paradigms, activation of protein kinase C (PKC) was necessary and sufficient for dopamine release, suggesting that G(q)-coupled receptors can induce DAT-mediated dopamine release through PKC, and providing a physiological role for the known regulation of DAT-mediated release by PKC. Activation of muscarinic receptors and PKC also induced release from a cell line expressing the norepinephrine transporter, suggesting that transport-mediated release might be relevant in further brain areas.