Organic cation transporter mRNA and function in the rat superior cervical ganglion

J Physiol. 2002 Aug 15;543(Pt 1):117-34. doi: 10.1113/jphysiol.2002.021170.


Reuptake of extracellular noradrenaline (NA) into superior cervical ganglion (SCG) neurones is mediated by means of the noradrenaline transporter (NAT, uptake 1). We now demonstrate by single-cell RT-PCR that mRNA of the organic cation transporter 3 (OCT3, uptake 2) occurs in rat SCG neurones as well. Furthermore, our RT-PCR analyses reveal the presence of mRNA for novel organic cation transporters 1 and 2 (OCTN1 and OCTN2), but not for OCT1 or OCT2 in the ganglion. Making use of the NAT as a powerful, neurone-specific transporter system, we loaded[3H]-N-methyl-4-phenylpyridinium ([3H]-MPP+) into cultured rat SCG neurones. The ensuing radioactive outflow from these cultures was enhanced by desipramine and reserpine, but reduced (in the presence of desipramine) by the OCT3 inhibitors cyanine 863, oestradiol and corticosterone. In contrast, cyanine 863 enhanced the radioactive outflow from cultures preloaded with [3H]-NA. Two observations suggest that a depletion of storage vesicles by cyanine 863 accounts for the latter phenomenon: first, the primary radioactive product isolated from supernatants of cultures loaded with [3H]-NA was the metabolite [3H]-DHPG; and second, inhibition of MAO significantly reduced the radioactive outflow in response to cyanine 863. The outflow of [3H]-MPP+ was significantly enhanced by MPP+, guanidine, choline and amantadine as potential substrates for OCT-related transmembrane transporters. However, desipramine at a low concentration essentially blocked the radioactive outflow induced by all of these substances with the exception of MPP+, indicating the NAT and not an OCT as their primary site of action. The MPP+-induced release of [3H]-MPP+ was fully prevented by a combined application of desipramine and cyanine 863. No trans-stimulation of [3H]-MPP+ outflow was observed by the OCTN1 and OCTN2 substrate carnitine at 100 microM. Our observations indicate an OCT-mediated transmembrane transport of [3H]-MPP+. Amongst the three OCTs expressed in the SCG, OCT3 best fits the profile of substrates and antagonists that cause trans-stimulation and trans-inhibition, respectively, of [3H]-MPP+ release.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Methyl-4-phenylpyridinium / pharmacokinetics
  • Animals
  • Biological Transport / physiology
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Catechol O-Methyltransferase
  • Cells, Cultured
  • Clorgyline / pharmacology
  • Gene Expression / physiology
  • Herbicides / pharmacokinetics
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Methyltransferases / antagonists & inhibitors
  • Methyltransferases / metabolism
  • Monoamine Oxidase / metabolism
  • Monoamine Oxidase Inhibitors / pharmacology
  • Neurons / cytology
  • Neurons / metabolism*
  • Norepinephrine / pharmacokinetics
  • Organic Anion Transporters, Sodium-Independent / genetics*
  • Organic Anion Transporters, Sodium-Independent / metabolism
  • Organic Cation Transport Proteins / genetics
  • Organic Cation Transport Proteins / metabolism
  • Organic Cation Transporter 1 / genetics
  • Organic Cation Transporter 1 / metabolism
  • Organic Cation Transporter 2
  • RNA, Messenger / analysis
  • Rats
  • Rats, Sprague-Dawley
  • Solute Carrier Family 22 Member 5
  • Solute Carrier Proteins
  • Superior Cervical Ganglion / cytology
  • Superior Cervical Ganglion / physiology*
  • Symporters
  • Tritium


  • Carrier Proteins
  • Herbicides
  • Membrane Proteins
  • Monoamine Oxidase Inhibitors
  • Organic Anion Transporters, Sodium-Independent
  • Organic Cation Transport Proteins
  • Organic Cation Transporter 1
  • Organic Cation Transporter 2
  • RNA, Messenger
  • SLC22A2 protein, human
  • SLC22A5 protein, human
  • Slc22a2 protein, rat
  • Slc22a4 protein, rat
  • Solute Carrier Family 22 Member 5
  • Solute Carrier Proteins
  • Symporters
  • organic anion transport protein 3
  • Tritium
  • Monoamine Oxidase
  • Methyltransferases
  • Catechol O-Methyltransferase
  • Clorgyline
  • 1-Methyl-4-phenylpyridinium
  • Norepinephrine