Effect of multiple dorsal rhizotomies on calcitonin gene-related peptide-like immunoreactivity in the lumbosacral dorsal spinal cord of the cat: a radioimmunoassay analysis.
Calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) was measured by radioimmunoassay in the cat lumbosacral dorsal spinal cord following unilateral dorsal rhizotomy of 5 consecutive dorsal roots. The dorsal rhizotomies greatly reduced but did not eliminate the CGRP-LI from the ipsilateral rhizotomized segments. The amount of CGRP-LI remaining in the rhizotomized segments was greatest in the most caudal segment (846 +/- 311 pmoles/g tissue) and decreased below 300 pmoles/g tissue in the remaining segments. When these values were compared to the intact contralateral side, the percent CGRP remaining ranged from 65% in the sacral segments to less than 20% in the lumbar segments. Rostral to the rhizotomized segments there was a gradual return of CGRP-LI to control levels within 3 segments. Small diameter primary afferent fibers are the only known source of CGRP within the dorsal spinal cord. These results suggest that the most likely origin of the CGRP that remained in the rhizotomized lumbar segments was the rostrally and caudally projecting branches of ipsilateral primary afferents that entered the spinal cord through intact dorsal roots caudal and rostral to the transected roots. These results support the hypothesis that small diameter primary afferents project several segments in the cat spinal cord.
Traub
R J
RJ
Neurobiology and Anesthesiology Branch, National Institute of Dental Research, Bethesda, MD 20892.
Iadarola
M J
MJ
Ruda
M A
MA
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis*; D002415:Cats; D008161:Lumbosacral Region; D011863:Radioimmunoassay; D013116:Spinal Cord / Q000032:analysis*; D013126:Spinal Nerve Roots / Q000502:physiology*
D015740:Calcitonin Gene-Related Peptide