Crossed and uncrossed projections to the cat sacrocaudal spinal cord: III. Axons expressing calcitonin gene‐related peptide immunoreactivity

Abstract

We have investigated the projection patterns of peptidergic small-diameter primary afferent fibers to the cat sacrocaudal spinal cord, a region associated with midline structures of the lower urogenital system and of the tail. Calcitonin gene-related peptide (CGRP)-immunoreactive (CGRP-IR) primary afferent fibers were observed within the superficial laminae, rostrally as the typical inverted U-shaped band that capped the separate dorsal horns (S1 to rostral S2) and caudally as a broad band that spanned the entire mediolateral extent of the fused dorsal horns (caudal S2 and caudal). Within the dorsal gray commissure, labeling was seen as a periodic vertical, midline band. CGRP-IR labeling was prevalent in an extensive mediolateral distribution at the base of the dorsal horn, originating from both lateral and medial collateral bundles that extend from the superficial dorsal horn. Some bundles, in part traveling within the dorsal commissure, conspicuously crossed the midline. In addition to the robust projection to the superficial dorsal horn, there was a more extensive distribution of CGRP-IR fibers within the deeper portions of the cat sacrocaudal dorsal horn than has been reported for other regions of the cat spinal cord. Presumably, these deep projections convey visceral information to projection or segmental neurons at the neck of the dorsal horn and in the region of the central canal. This deep distribution overlaps the reported projections of the pelvic and pudendal nerves. In addition, the contralateral projections of CGRP-IR fibers may form an anatomical substrate of the bilateral receptive fields for selective dorsal horn neurons. The density and variety of CGRP-IR projection patterns is a reflection of the functional attributes of the innervated structures.

Calpain fosters the hyperexcitability of motoneurons after spinal cord injury and leads to spasticity

“…Diversity of KCC2 expression between motoneurons innervating distinct muscles (Ueno et al, 2002) or variation in the sacral inhibitory circuitry (Jankowska et al, 1978) may account for this discrepancy. Spinal cord level-specific differences in neuronal responses to SCI are probable with respect to the special anatomy and function of the sacrocaudal spinal cord (Ritz et al, 1992; Ritz et al, 2001).…”

Spinal Central Effects of Peripherally Applied Botulinum Neurotoxin A in Comparison between Its Subtypes A1 and A2

“…Recent reports have also shown bilateral antinociceptive effects of BoNT/A1 following unilateral, peripheral toxin injection (32, 34, 35). As a possible mechanism by which unilateral BoNT/A1 administration can exert contralateral antinociceptive actions, we suggest that the toxin might spread to contralateral dorsal horn neurons via a crossing fiber mechanism (36) and/or a transsynaptic cell-to-cell trafficking mechanism within the spinal cord. Our assumption is supported by the present immunohistochemical finding that cSNAP-25 was bilaterally distributed in the dorsal horns at the level of L5 (see Figures 4 and 5).…”

Spastic Long-Lasting Reflexes of the Chronic Spinal Rat Studied In Vitro

“…We had not anticipated the large contralateral reflexes seen in the in vitro preparation, although in retrospect, this was a mistake due to the special anatomy and function of the sacrocaudal spinal cord (Jankowska et al 1978;Ritz et al 1989Ritz et al , 1991Ritz et al , 2001). There is crossed segmental reflex control in the sacral cord, which is not seen at higher spinal segments, including crossed disynaptic inhibition, crossed monosynaptic excitation from Ia afferents, and crossed presynaptic inhibition of afferents (Akatani et al 2002;Harvey et al 1999;Jankowska et al 1978;Wada and Shikaki 1999).…”