Brief, repeated exposure to substrates down-regulates dopamine transporter function in Xenopus oocytes in vitro and rat dorsal striatum in vivo.
In heterologous expression systems, dopamine transporter (DAT) cell-surface localization is reduced after relatively prolonged exposure to d-amphetamine (AMPH) or dopamine (DA), suggesting a role for substrate-mediated regulation of transporter function. Here, we investigated whether brief, repeated periods of substrate exposure modulated transporter function, first, in an in vitro model system and, second, in intact rat brain. In human DAT-expressing Xenopus laevis oocytes, repeated exposure to low micromolar concentrations of DA, AMPH or tyramine markedly reduced transport-mediated currents. This functional down-regulation was attenuated by inclusion of a protein kinase C (PKC) inhibitor and probably reflects DAT redistribution, as cell-surface [3H]WIN 35 428 binding was significantly lower following DA exposure. High-speed chronoamperometry was used to measure clearance of exogenously applied DA in dorsal striatum (STR) and nucleus accumbens (NAc) of anesthetized rats. In STR, frequent (every 2 min) applications of DA altered DA clearance parameters in a manner consistent with profound down-regulation of DAT function. Similar changes were not observed in NAc or after repeated vehicle (ascorbic acid) application. Together, our results suggest that brief, repeated periods of substrate exposure lead to rapid down-regulation of DAT activity and that this type of regulation can occur in vivo in STR, but not NAc.
Gulley
Joshua M
JM
Department of Pharmacology and Neuroscience Program, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. joshua.gulley@uchsc.edu
Doolen
Suzanne
S
Zahniser
Nancy R
NR
D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000494:pharmacology*; D050483:Dopamine Plasma Membrane Transport Proteins; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D008562:Membrane Glycoproteins; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008845:Microinjections; D009419:Nerve Tissue Proteins; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D018075:RNA, Complementary / Q000008:administration & dosage; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014439:Tyramine / Q000494:pharmacology; D014981:Xenopus
D050483:Dopamine Plasma Membrane Transport Proteins; D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D018075:RNA, Complementary; C493216:Slc6a3 protein, rat; D000661:Amphetamine; D011493:Protein Kinase C; C070515:bisindolylmaleimide I; D004298:Dopamine; D014439:Tyramine