Vol. 289, Issue 1, 278-284, April 1999

Modulation of Amphetamine-Stimulated [³H]Dopamine Release from Rat Pheochromocytoma (PC12) Cells by  Type 2 Receptors¹

John K. Weatherspoon and Linda L. Werling

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

An important regulatory mechanism of synaptic dopamine (DA) levels is activation of the dopamine transporter (DAT), which is a target for many drugs of abuse, including amphetamine (AMPH).  receptors are located in dopaminergic brain areas critical to reinforcement. We found previously that agonists at ₂ receptors enhanced the AMPH-stimulated release of [³H]DA from slices of rat caudate-putamen. In the present study, we modeled this response in undifferentiated pheochromocytoma-12 (PC12) cells, which contain both the DAT and ₂ receptors but not neural networks that can complicate investigation of individual neuronal mechanisms. We found that enhancement of AMPH-stimulated [³H]DA release by the  agonist (+)-pentazocine was blocked by ₂ receptor antagonists. Additionally, the reduction in the effect of (+)-pentazocine by the inclusion of ethylene glycol bis(-aminoethyl ether)-N,N,N',N'-tetraacetic acid led us to hypothesize that ₂ receptor activation initiated a Ca²⁺-dependent process that resulted in enhancing the outward flow of DA via the DAT. The source of Ca²⁺ required for the enhancement of reverse transport did not appear to be via N- or L-type voltage-dependent Ca²⁺ channels, because it was not affected by nitrendipine or -conotoxin. However, two inhibitors of Ca²⁺/calmodulin-dependent protein kinase II blocked enhancement in AMPH-stimulated release by (+)-pentazocine. Our findings suggest that ₂ receptors are coupled to the DAT via a Ca²⁺/calmodulin-dependent protein kinase II transduction system in PC12 cells, and that ₂ receptor antagonists might be useful in the treatment of drug abuse by blocking elevation of DA levels via reversal of the DAT.