Distribution of small-diameter primary afferents containing oligosaccharide residues recognized by monoclonal antibody LA4 in the dorsal horn of the cat

Abstract

Small-diameter primary afferents expressing oligosaccharide residues recognized by the monoclonal antibody LA4 constitute a newly described primary afferent population in the cat. LA4-immunoreactive primary afferents are found mainly in lamina II (LII) at all levels of the cat spinal cord. However, within LII immunoreactive fibers are most concentrated in outer LII and practically absent from the inner third of the lamina. In addition at sacral levels, a lateral bundle of immunoreactive fibers enters laminae V–VII. The distribution pattern and the type of oligosaccharide expressed by LA4-immunoreactive fibers suggest that they may be homologous to primary afferents shown in the rat to contain fluoride-resistant acid phosphatase activity. However, in the rat spinal cord the whole of inner LII is the main projection area of LA4-immunoreactive fibers (Alvarez et al., J. Neurocytol., 18 (1989) 611–629). This difference in the location of primary afferents within LII may reflect a species difference in the physiology of LII inner.