Increased expression of metabotropic glutamate receptor subtype 1 on spinothalamic tract neurons following spinal cord injury in the rat

Spinal cord injury (SCI) leads to an increase in metabotropic glutamate receptor subtype 1 (mGluR1) immunoreactivity in the peri-lesion area. The increased expression of mGluR1 parallels the development of thermal hyperalgesia and mechanical allodynia and has been suggested to contribute to the development and maintenance of chronic central pain (CCP) syndromes resulting from SCI. However, expression of mGluR1 has not been directly shown to increase on cells in the pain pathway. Therefore, the expression of mGluR1 on spinothalamic tract (STT) neurons was quantified using confocal imaging and densiometric analysis in normal, sham, and SCI rats. Contusion SCI produced an increase in mGluR1 expression on STT cells in both the cervical enlargement and the spinal section just rostral to contusion SCI. These results suggest that mGluR1 is expressed on neurons that modulate pain transmission and expression on these cells increases following injury, supporting the hypothesis that mGluR1 contributes to CCP following SCI.