Group I mGluRs coupled to G proteins are regulated by tyrosine kinase in dopamine neurons of the rat midbrain

J Neurophysiol. 2001 Jun;85(6):2490-7. doi: 10.1152/jn.2001.85.6.2490.


Metabotropic glutamate receptors (mGluRs) modulate neuronal function via different transduction mechanisms that are either dependent or independent on G-protein function. Here we investigated, using whole cell patch-clamp recordings in combination with fluorimetric measurements of intracellular calcium concentration ([Ca(2+)](i)), the metabolic pathways involved in the responses induced by group I mGluRs in dopamine neurons of the rat midbrain. The inward current and the [Ca(2+)](i) increase caused by the group I mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG, 100 microM) were permanently activated and subsequently abolished in cells loaded with the nonhydrolizable GTP-analogue GTP-gamma-S (600 microM). In addition, when GDP-beta-S (600 microM) was dialyzed into the cells to produce the blockade of the G proteins, the DHPG-dependent responses were reduced. When the tissue was bathed with the phospholipase C inhibitor 1-[6[[(17 beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]exyl]-1H-pyrrole-2,5-dione (10 microM), the DHPG-induced calcium transients slightly diminished but the associated inward currents were not affected. Interestingly, a substantial depression of the DHPG-induced inward current and transient increase of [Ca(2+)](i) was caused by the protein tyrosine kinase inhibitors tyrphostin B52 (40 microM) and 4',5,7-trihydroxyisoflavone (genistein; 40 microM), whereas genistein's inactive analogue 4',5,7-trihydroxyisoflavone-7-glucoside (40 microM) was ineffective. The blockade of the Src family of tyrosine kinase by 4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (20 microM), mitogen-activated protein kinase by 2'-amino-3' methoxyflavone (50 microM), and protein kinase C by staurosporine (1 microM) had no effect on the cellular responses caused by DHPG. The mGluR5-selective antagonist 2-methyl-6-(phenylethynyl)-pyridine (10--100 microM) did not affect the actions of DHPG. Thus our results indicate that the responses, mainly mediated by mGluRs1 in dopamine neurons, are activated by intracellular mechanisms coupled to G proteins and regulated by tyrosine kinases.

MeSH terms

  • Animals
  • Dopamine / physiology*
  • Enzyme Activation / physiology
  • Enzyme Inhibitors / pharmacology
  • Estrenes / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Female
  • GTP-Binding Proteins / metabolism*
  • Genistein / pharmacology
  • Glycine / analogs & derivatives
  • Glycine / pharmacology
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
  • Guanosine Diphosphate / analogs & derivatives*
  • Guanosine Diphosphate / pharmacology
  • Male
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Mesencephalon / cytology
  • Neurons / enzymology*
  • Patch-Clamp Techniques
  • Phosphodiesterase Inhibitors / pharmacology
  • Protein Kinase C / metabolism
  • Protein-Tyrosine Kinases / metabolism*
  • Pyrrolidinones / pharmacology
  • Rats
  • Rats, Wistar
  • Receptors, Metabotropic Glutamate / metabolism*
  • Resorcinols / pharmacology
  • Thionucleotides / pharmacology
  • Type C Phospholipases / metabolism
  • Tyrphostins / pharmacology


  • Enzyme Inhibitors
  • Estrenes
  • Excitatory Amino Acid Antagonists
  • Phosphodiesterase Inhibitors
  • Pyrrolidinones
  • Receptors, Metabotropic Glutamate
  • Resorcinols
  • Thionucleotides
  • Tyrphostins
  • metabotropic glutamate receptor type 1
  • 1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione
  • Guanosine Diphosphate
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • 3,5-dihydroxyphenylglycine
  • guanosine 5'-O-(2-thiodiphosphate)
  • Genistein
  • Protein-Tyrosine Kinases
  • Protein Kinase C
  • Type C Phospholipases
  • GTP-Binding Proteins
  • Glycine
  • Dopamine