Journal of molecular neuroscience : MN
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The distribution of peptides thought to be involved in pain modulation--substance P, calcitonin gene-related peptide (CGRP), and enkephalin--were studied in the spinal cord and dorsal root ganglia of polyarthritic rats and in rats with one sciatic nerve sectioned prior to induction of arthritis. In arthritic rats there was a bilateral increase of CGRP- and substance P-immunoreactive fibers and appearance of enkephalin-immunoreactive cell bodies in the dorsal horn of the lumbar (L4) spinal cord when compared to controls. In the corresponding dorsal root ganglia there were significant increases of CGRP- (P less than 0.02) and substance P- (P less than 0.001) immunoreactive cell bodies compared to controls. ⋯ In the ipsilateral L4 ganglia CGRP- (P less than 0.02) and substance P- (P less than 0.02) immunoreactive cells were significantly decreased compared to the contralateral side. The data suggest that pain perception is linked to complex interactions between CGRP, substance P, and enkephalin in sensory pathways and an intact peripheral input. The loss of CGRP-immunoreactive motoneurons may reflect muscular dysfunction associated with the arthritic condition.