Journal of Neuroscience, Vol 14, 1576-1583, Copyright © 1994 by Society for Neuroscience
Glutamate receptor gene expression in spinal cord of arthritic rats
DE Pellegrini-Giampietro, S Fan, B Ault, BE Miller and RS Zukin
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461.
Injury to peripheral tissue leads to hyperalgesia that appears to be partly
mediated by functional changes at the level of the spinal cord. Glutamate
receptors are thought to play a role in acute and short-term (minutes to
hours) spinal cord nociceptive responses and may be involved in prolonged
or chronic pain (hours to days). We used in situ hybridization to examine
AMPA/kainate (GluR1, GluR2, and GluR3) and NMDA (NR1) receptor gene
expression in spinal cord following induction of prolonged inflammation by
a unilateral intraarticular injection of lipopolysaccharide (LPS; 10
micrograms) into the hindpaw. In control rats, GluR1 expression was
prominent throughout the layers of the gray matter of the spinal cord.
Microscopic examination revealed labeling of neuronal cell somata in all
major nuclei. GluR2 was abundant in substantia gelatinosa and motor nuclei;
emulsion-dipped sections exhibited intense labeling over densely packed
neurons in the superficial laminae of dorsal horn and individual
motoneurons of ventral horn. GluR3 and NR1 were expressed at low levels
throughout spinal cord gray matter. One day after LPS injection, when joint
swelling was maximal, GluR1 expression was bilaterally decreased by 25% in
the substantia gelatinosa at the level of the lumbar cord. In contrast, no
significant change was apparent in GluR2, GluR3, or NR1 expression in any
nucleus of the cord. At 72 hr after injection, when joint diameter
approached control values, all four transcripts were expressed at near
control levels. These findings provide evidence for a specific decrease in
GluR1 expression in the cord in response to joint inflammation.