Activation of presynaptic group I metabotropic glutamate receptors enhances glutamate release in the rat spinal cord substantia gelatinosa

Neurosci Lett. 2004 May 6;361(1-3):220-4. doi: 10.1016/j.neulet.2003.12.075.

Abstract

The activation of group I metabotropic glutamate receptors (mGluRs) produces a long-term potentiation of sensory transmission in the substantia gelatinosa (SG) region of the spinal cord (Prog. Brain Res. 129 (2000) 115). The mechanism(s) responsible for the induction of this potentiation is not known. Using rat spinal cord slice preparation and patch-clamp recordings, here we show, that the activation of the group I mGluRs by (S)-3,5-dihydroxyphenylglycine (DHPG, 1 microM), the mGluR1/5 agonist, increased the frequency of both activity-dependent spontaneous EPSCs, and activity-independent miniature EPSCs (mEPSCs). However, DHPG did not affect amplitude of mEPSCs. The effects of DHPG were not seen in the presence of the preferential mGluR1 antagonist CPCCOEt (10 microM). On the other hand, 2-methyl-6-(phenylethynyl)-pyridine (10 microM), a selective mGluR5 antagonist, blocked the DHPG facilitation present during the wash-out of the drug. This novel facilitating effect of the group I mGluR activation on glutamate release is the first report of a direct facilitatory action of both mGluR1 and mGluR5 subtypes on sensory transmission in the spinal cord SG region. These results indicate the potential contribution of synaptic activation of these facilitatory autoreceptors in plasticity of primary afferent neurotransmission.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Afferent Pathways / drug effects
  • Afferent Pathways / metabolism*
  • Animals
  • Excitatory Amino Acid Agonists / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / physiology
  • Female
  • Glutamic Acid / metabolism*
  • In Vitro Techniques
  • Male
  • Neurons, Afferent / drug effects
  • Neurons, Afferent / metabolism
  • Presynaptic Terminals / drug effects
  • Presynaptic Terminals / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Metabotropic Glutamate 5
  • Receptors, Metabotropic Glutamate / agonists
  • Receptors, Metabotropic Glutamate / antagonists & inhibitors
  • Receptors, Metabotropic Glutamate / metabolism*
  • Substantia Gelatinosa / drug effects
  • Substantia Gelatinosa / metabolism*
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology
  • Up-Regulation / drug effects
  • Up-Regulation / physiology

Substances

  • Excitatory Amino Acid Agonists
  • Excitatory Amino Acid Antagonists
  • Grm5 protein, rat
  • Receptor, Metabotropic Glutamate 5
  • Receptors, Metabotropic Glutamate
  • metabotropic glutamate receptor type 1
  • Glutamic Acid