Calcitonin gene-related peptide immunoreactivity in the cat lumbosacral spinal cord and the effects of multiple dorsal rhizotomies.
This study determined the extent of the rostral projection of calcitonin gene-related peptide-like immunoreactive (CGRP-IR) primary afferents in the cat lumbosacral spinal cord. To do this we examined the distribution of CGRP-like immunoreactivity (CGRP-LI) contralateral and ipsilateral to multiple dorsal rhizotomies. In the contralateral dorsal spinal cord, CGRP-IR fibers were mostly observed in Lissauer's tract, the dorsal columns, and laminae I, II, and V. Fewer CGRP-IR fibers were observed in laminae III, IV, and VI and the area around the central canal. The location of the CGRP-LI suggests that the afferents arose from nociceptors. Unilateral dorsal rhizotomies of five consecutive segments in the lumbar enlargement caused a substantial although incomplete loss of CGRP-LI in the rhizotomized dorsal spinal cord ipsilateral to the lesions. The majority of the remaining CGRP-IR fibers were located in Lissauer's tract, the dorsal columns, and the lateral part of laminae I and V. Ventral rhizotomies or an ipsilateral hemisection in the most rostral rhizotomized segment, in addition to the dorsal rhizotomies, had no noticeable effect upon the density or location of the remaining CGRP-LI. These results suggest that the majority of the CGRP-LI within the rhizotomized region of spinal cord was contained within branches of small-diameter primary afferents that entered the spinal cord through intact dorsal roots located caudal to the rhizotomized segments of spinal cord. It is concluded that CGRP-IR small-diameter primary afferents are capable of projecting at least five segments beyond their segment of entry and supplying collaterals to the superficial and deeper layers of the dorsal horn involved in the processing of nociceptive information.
Traub
R J
RJ
Neurobiology and Anesthesiology Branch, National Institute of Dental Research, Bethesda, Maryland 20892.
Solodkin
A
A
Ruda
M A
MA
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis*; D002415:Cats; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D009434:Neural Pathways / Q000033:anatomy & histology; D009475:Neurons, Afferent / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D013116:Spinal Cord / Q000033:anatomy & histology / Q000378:metabolism* / Q000502:physiology
D015740:Calcitonin Gene-Related Peptide