Vol. 301, Issue 1, 306-314, April 2002

₂-Receptor Regulation of Dopamine Transporter via Activation of Protein Kinase C

Alicia E. Derbez, Rupal M. Mody and Linda L. Werling

Department of Pharmacology, The George Washington University Medical Center, Washington, DC

The elucidation of the mechanisms underlying ₂-receptor activation and signal transduction is crucial to the understanding of ₂-receptor function. Previous studies in our laboratory have demonstrated ₂-receptor-mediated regulation of the dopamine transporter (DAT) as measured by amphetamine-stimulated release of [³H]dopamine (DA) from both rat striatal slices and PC12 cells. The regulation of the DAT in the PC12 cell model was dependent upon activation of Ca²⁺/calmodulin-dependent kinase II. We have now studied the second messenger systems involved in ₂-receptor-mediated regulation of amphetamine-stimulated [³H]DA release in rat striatal slices, including Ca²⁺/calmodulin-dependent kinase II, protein kinase C, and sources of calcium required for the enhancement of release produced by ₂-receptor activation. The Ca²⁺/calmodulin-dependent kinase II inhibitors 1-[N,O-bis-(5-isoquionolinesulfonyl)]-N-methyl-L-tyrosyl-4-phenylpiperazine and N-[2-[[[3-(4'-chlorophenyl)-2-propenyl]methylamino]methyl]phenyl]-N-(2-hydroxyethyl)-4'-methoxy-benzenesulfonamide phosphate did not significantly affect the (+)-pentazocine-mediated enhancement of amphetamine-stimulated [³H]DA release. However, we found that an inhibitor of protein kinase C, 3-[1-[3-(dimethylamino)propyl]-1H-indol-3-yl)-1H-pyrrole-2,5-dione, blocks the (+)-pentazocine-mediated enhancement in rat striatal slices. The protein kinase C activator phorbol 12-myristate 13-acetate, but not the inactive isophorbol 4,9,12,13,20-pentahydroxytiglia-1,6-dien-3-one, enhanced the amphetamine-stimulated [³H]DA release comparable to the enhancement seen by (+)-pentazocine alone. Additionally, the L-type voltage-dependent calcium channel inhibitor nitrendipine or prior treatment with thapsigargin, but not the N-type voltage-dependent calcium channel -conotoxin MVIIA, attenuated the (+)-pentazocine-mediated enhancement. Together, these data suggest that activation of ₂-receptors results in the regulation of DAT activity via a calcium- and protein kinase C-dependent signaling mechanism.