Journal of Neuroscience, Vol 9, 195-205, Copyright © 1989 by Society for Neuroscience
A quantitative study of the coexistence of peptides in varicosities within the superficial laminae of the dorsal horn of the rat spinal cord
MM Tuchscherer and VS Seybold
Department of Cell Biology and Neuroanatomy, University of Minnesota, Minneapolis 55455.
While several peptides have been shown to coexist in perikarya within
dorsal root ganglia of rat, coexistence of peptides has not been confirmed
in axons associated with these neurons. In this study, the coexistence of
substance P (SP) with somatostatin (SOM), calcitonin gene-related peptide
(CGRP), dynorphin A 1-8 (DYN), neurotensin (NT), galanin (GAL), and 5-HT in
varicosities was visualized using fluorescence immunohistochemistry.
Densities of immunoreactive varicosities within laminae I and II of the
dorsal horn of the rat spinal cord were quantified by computer-assisted
image analysis. Decreases in densities of immunoreactive varicosities as a
result of multiple unilateral dorsal rhizotomies were used to determine
proportions of immunoreactive varicosities associated with primary afferent
neurons. Three observations were made. (1) Dorsal rhizotomy depleted
greater than one-third of the varicosities individually immunoreactive for
SP, SOM, GAL, or DYN, confirming the association of these peptides with
primary afferent neurons. (2) SP coexisted with CGRP, GAL, and DYN in
varicosities within the dorsal horn of normal animals. (3) CGRP-, SP+CGRP-,
and SP+GAL-immunoreactive varicosities were nearly depleted following
dorsal rhizotomy. The depletion of these peptides, particularly in
combination, indicates that they may be used as markers for varicosities of
some primary afferent neurons within the superficial laminae of the dorsal
horn of the rat spinal cord.
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