Modulation of dopamine transporter activity by nicotinic acetylcholine receptors and membrane depolarization in rat pheochromocytoma PC12 cells.
To elucidate the regulation of the rat dopamine transporter (rDAT), we established several PC12 variants overexpressing the rDAT. Treating these cells with a nicotinic agonist (1,1-dimethyl-4-phenylpiperazinium iodide, 30 microM) depolarized the plasma membrane potential from -31 +/- 2 to 43 +/- 5 mV and inhibited rDAT activity significantly in a calcium- and protein kinase C-independent manner. Membrane depolarization by a high external K+ concentration or two K+ channel blockers (tetraethylammonium hydroxide and BaCl2) also resulted in a marked inhibition of rDAT activity. Such inhibition of dopamine uptake is due to a reduction in Vmax, with no marked effect on the Km for dopamine. The potency of cocaine in inhibiting dopamine uptake was not significantly altered, whereas that of amphetamine was slightly enhanced by membrane depolarization. Removing extracellular Ca2+ or blocking the voltage-sensitive L-type calcium channels using nifedipine did not exert any significant effect on the inhibition of rDAT activity by depolarization. These data confirm that calcium influx on depolarization is not required for inhibition of the rDAT. Collectively, our data suggest that rDAT activity can be altered by a neurotransmitter that modulates the membrane potential, thus suggesting an exquisite mechanism for the fine-tuning of dopamine levels in the synapse.
Huang
C L
CL
Division of Neuroscience, Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, Republic of China.
Chen
H C
HC
Huang
N K
NK
Yang
D M
DM
Kao
L S
LS
Chen
J C
JC
Lai
H L
HL
Chern
Y
Y
D000310:Adrenal Gland Neoplasms; D000818:Animals; D017609:Barium Compounds / Q000494:pharmacology; D001692:Biological Transport; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D002712:Chlorides / Q000494:pharmacology; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins; D007700:Kinetics; D008562:Membrane Glycoproteins; D008564:Membrane Potentials / Q000502:physiology; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D016716:PC12 Cells; D018408:Patch-Clamp Techniques; D010673:Pheochromocytoma; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology; D011869:Radioligand Assay; D051381:Rats; D011978:Receptors, Nicotinic / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D019789:Tetraethylammonium / Q000494:pharmacology; D014162:Transfection
D017609:Barium Compounds; D002352:Carrier Proteins; D002712:Chlorides; D050483:Dopamine Plasma Membrane Transport Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011978:Receptors, Nicotinic; D011994:Recombinant Proteins; C024986:barium chloride; D004246:Dimethylphenylpiperazinium Iodide; D019789:Tetraethylammonium; D004298:Dopamine