Abstract
Plastic changes in the amygdala and limbic cortex networks have been widely shown in chronic pain. We have here investigated the role of group I metabotropic glutamate receptors (mGluRs) in the basolateral amygdala (BLA) pre-infra-limbic (PL-IL) divisions of the medial prefrontal cortex (mPFC) neuron connections after carrageenan-induced inflammatory pain in the rat. Intra-plantar injection of carrageenan decreased either spontaneous or mechanically/electrically evoked activity of PL cortex pyramidal neurons which responded with excitation in a way prevented by CPCOOEt, a selective mGluR1 antagonist, though not by MPEP, a selective mGluR5 antagonist. Accordingly, intra-BLA microinjection of DHPG, a group I mGluR agonist, caused PL cortex neuron activity depression, antagonized by CPCCOEt. CPCOOEt, but not MPEP, reduced also carrageenan-induced mechanical allodynia. The PL cortex cell deactivation in inflammatory pain condition was associated with increased GABA (conversely glutamate was decreased) in the PL/IL cortex. The local application of bicuculline, a GABA(A) receptor selective antagonist, reduced mechanical allodynia. An over-expression of mGluR1, but not mGluR5, have been observed in the PL-IL cortex after inflammatory pain suggesting an increased mGluR1-dependent cross-talk among BLA and IL-PL cortex neurons in inflammatory pain conditions. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.
Copyright © 2012. Published by Elsevier Ltd.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Action Potentials / drug effects
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Action Potentials / physiology
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Amygdala / drug effects
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Amygdala / physiology*
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Animals
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Bicuculline / pharmacology
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Carrageenan
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Chromones / administration & dosage
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Chromones / pharmacology
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Disease Models, Animal
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Electric Stimulation / methods
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Excitatory Amino Acid Agonists / pharmacology
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Excitatory Amino Acid Antagonists / pharmacology
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Formaldehyde / pharmacology
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GABA Antagonists / pharmacology
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Gene Expression / drug effects
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Gene Expression / physiology
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Glycine / administration & dosage
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Glycine / analogs & derivatives
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Glycine / pharmacology
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Male
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Neural Inhibition / drug effects
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Neural Inhibition / physiology
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Neural Pathways / drug effects
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Neural Pathways / physiopathology
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Neuronal Plasticity / drug effects
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Neuronal Plasticity / physiology
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Pain / physiopathology*
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Physical Stimulation / methods
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Prefrontal Cortex / drug effects
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Prefrontal Cortex / physiology*
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Pyramidal Cells / drug effects
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Pyramidal Cells / physiology
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Pyridines / administration & dosage
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Pyridines / pharmacology
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Rats
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Rats, Wistar
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Receptor, Metabotropic Glutamate 5
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Receptors, Metabotropic Glutamate / biosynthesis
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Receptors, Metabotropic Glutamate / physiology*
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Resorcinols / administration & dosage
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Resorcinols / pharmacology
Substances
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7-(hydroxyimino)cyclopropan(b)chromen-1a-carbxoylic acid ethyl ester
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Chromones
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Excitatory Amino Acid Agonists
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Excitatory Amino Acid Antagonists
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GABA Antagonists
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Grm5 protein, rat
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Pyridines
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Receptor, Metabotropic Glutamate 5
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Receptors, Metabotropic Glutamate
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Resorcinols
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metabotropic glutamate receptor type 1
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Formaldehyde
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3,5-dihydroxyphenylglycine
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6-methyl-2-(phenylethynyl)pyridine
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Carrageenan
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Glycine
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Bicuculline