J Korean Assoc Maxillofac Plast Reconstr Surg.  2004 Sep;26(5):461-468.

Roles of metabotropic glutamate receptors on excitatory synaptic transmission in rat trigeminal caudal neurons

Affiliations
  • 1Department of Oral Physiology, Genome Research Center for Immune Disorders, College of Dentistry, Wonkwang University, Korea.
  • 2Department of Oral & Maxillofacial Surgery, College of Dentistry, Wonkwang University, Korea.
  • 3Wonkwang Dental Research Institute, Korea.

Abstract

The caudal subnucleus of the spinal trigeminal nucleus (medullary dorsal horn : MDH) is implicated in the processing of nociceptive information in the orofacial region. Whole cell patch clamp recordings were carried out on MDH neurons in the brainstem slices of neonatal rats to investigate the roles of metabotropic glutamate receptors on excitatory synaptic transmission. In the presence of strychnine (1 microM) and bicuculline (20 microM), spontaneous inward currents at -70 mV were observed. Spontaneous excitatory postsynaptic currents (sEPSCs) were mediated by non-NMDA and NMDA receptors. The specific AMPA receptor antagonist GYKI 52466 (50 microM) completely blocked the non-NMDA mediated sEPSCs, indicating that they are mediated by an AMPA-preferring receptor. Group I, II metabotropic glutamate receptor (mGluR) agonist ACPD (20 microM) significantly decreased the average sEPSCs frequency. No significant effect on sEPSCs amplitude was observed. Frequency of miniature excitatory postsynaptic currents (mEPSCs) was significantly decreased by 20 microM ACPD, but amplitude of mEPSCs was not changed. The specific mGluR 2, 3 agonist DCG-IV (3 microM) reduced mEPSCs frequency, but did not change mEPSCs amplitude. There were no significant changes in the average sEPSCs frequency and amplitude. The mGluR 1, 5 agonist DHPG (100 microM) decreased sEPSCs and mEPSCs frequency, but had no effects on sEPSCs and mEPSCs amplitude. These data suggest that the activation of metabotropic glutamate receptors, via its presynaptic inhibition, can influence the excitatory synaptic transmission of MDH neurons.

Keyword

Trigeminal caudal neuron; Metabotropic glutamate receptor; Excitatory synaptic transmission; Presynaptic inhibition

MeSH Terms

Animals
Bicuculline
Brain Stem
Excitatory Postsynaptic Potentials
Horns
Neurons*
Rats*
Receptors, AMPA
Receptors, Metabotropic Glutamate*
Receptors, N-Methyl-D-Aspartate
Strychnine
Synaptic Transmission*
Trigeminal Nucleus, Spinal
Bicuculline
Receptors, AMPA
Receptors, Metabotropic Glutamate
Receptors, N-Methyl-D-Aspartate
Strychnine
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