Role of metabotropic glutamate receptor 1 in the basolateral amygdala-driven prefrontal cortical deactivation in inflammatory pain in the rat.
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'.
Department of Experimental Medicine, Division of Pharmacology "L. Donatelli", The Second University of Naples (SUN), Via Costantinopoli 16, 80138 Naples, Italy.
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D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000679:Amygdala / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002351:Carrageenan; D002867:Chromones / Q000008:administration & dosage / Q000494:pharmacology; D004195:Disease Models, Animal; D004558:Electric Stimulation / Q000379:methods; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005557:Formaldehyde / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D005998:Glycine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009434:Neural Pathways / Q000187:drug effects / Q000503:physiopathology; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D010812:Physical Stimulation / Q000379:methods; D017397:Prefrontal Cortex / Q000187:drug effects / Q000502:physiology*; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology; D011725:Pyridines / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000096:biosynthesis / Q000502:physiology*; D012118:Resorcinols / Q000008:administration & dosage / Q000494:pharmacology
C117789:7-(hydroxyimino)cyclopropan(b)chromen-1a-carbxoylic acid ethyl ester; D002867:Chromones; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; C578937:Grm5 protein, rat; D011725:Pyridines; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D012118:Resorcinols; C104077:metabotropic glutamate receptor type 1; D005557:Formaldehyde; C079215:3,5-dihydroxyphenylglycine; C121465:6-methyl-2-(phenylethynyl)pyridine; D002351:Carrageenan; D005998:Glycine; D001640:Bicuculline