Upregulation of Group I metabotropic glutamate receptors in neurons and astrocytes in the dorsal horn following spinal cord injury

• Published in: Experimental neurology Vol. 195; no. 1; pp. 236 - 243
• Main Authors: Gwak, Young Seob, Hulsebosch, Claire E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01-09-2005; Elsevier
• Subjects: Animals; Astrocytes; Astrocytes - metabolism; Biological and medical sciences; Cell Count; Central neuropathic pain; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Fluorescent Antibody Technique - methods; Functional Laterality; Glial Fibrillary Acidic Protein - metabolism; Injuries of the nervous system and the skull. Diseases due to physical agents; Medical sciences; Metabotropic glutamate receptor; Neurology; Neurons - classification; Neurons - metabolism; Phosphopyruvate Hydratase - metabolism; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate - classification; Receptors, Metabotropic Glutamate - genetics; Receptors, Metabotropic Glutamate - metabolism; Spinal Cord Injuries - metabolism; Spinal Cord Injuries - pathology; Spinal cord injury; Spinal dorsal horn; Time Factors; Traumas. Diseases due to physical agents; Up-Regulation - physiology; Spinal dorsal horn; Central neuropathic pain; Spinal cord injury; Astrocytes; Metabotropic glutamate receptor; Spinal cord; Group I mglu glutamate receptor; Rat; Neuroglia; Central nervous system; Glutamate receptor; Posterior spinal horn; Peripheral neuropathy; Pain; Spinal cord trauma; Hyperexcitability; Receptor protein; Peripheral nerve disease; G protein; Biological receptor; Postoperative; Nervous system diseases; Early phase; Rodentia; Astrocyte; Long term; Vertebrata; Chronic; Mammalia; Neuron; Metabotropic receptor; Animal; Central nervous system disease; Intracellular; Spinal cord disease
• ISSN: 0014-4886; 1090-2430
• DOI: 10.1016/j.expneurol.2005.05.012

Of the glutamate receptor types, the metabotropic glutamate receptors (mGluRs) are G proteins coupled and can initiate a number of intracellular pathways leading to hyperexcitability of spinal neurons. In this study, we tested the expression of mGluRs to determine which cell types might contribute to sustained neuronal hyperexcitability in the lumbar enlargement with postoperative day (POD) 7 (early), 14 (late), and 30 (chronic phase) following spinal cord injury (SCI) by unilateral hemisection at T13 in Sprague–Dawley rats. Expression was determined by confocal analyses of immunocytochemical reaction product of neurons (NeuN positive) and astrocytes (GFAP positive) in the dorsal horn on both sides of the L4 segment. Neurons were divided into two sizes: small (<20 μm) and large (>35 μm), for physiological reasons. We report a significant increase of mGluR
1 expression in large and small neurons of the dorsal horn on both sides of the cord in late and chronic phases when compared to control sham groups. Expression of mGluR
2/3 significantly increased in large neurons on the ipsilateral (hemisected) side in the late phase. Expression of mGluR
5 significantly increased in large neurons in early, late, and chronic phases. In addition, mGluR
1 and mGluR
5 expression after hemisection was significantly increased in astrocytes in early, late, and chronic phases; whereas mGluR
2/3 did not display any significant changes. In conclusion, our data demonstrate long-term changes in expression levels of Group I mGluRs (mGluR
1 and mGluR
5) in both neurons and astrocytes in segments below a unilateral SCI. Thus, permanent alterations in dorsal horn receptor expression may play important roles in transmission of nociceptive responses in the spinal cord following SCI.