title: Large diameter primary afferent input is required for expression of the Cat-301 proteoglycan on the surface of motor neurons.
abstract: The expression of a cell surface proteoglycan, recognized by monoclonal antibody Cat-301, is regulated by neuronal activity in early life. Here we report that the expression of the Cat-301 proteoglycan on motor neurons depends on primary afferent input in the early postnatal period. Previously we showed that in two different systems, Y-cells in the cat lateral geniculate nucleus and motor neurons in the hamster spinal cord, the expression of the Cat-301 antigen requires neuronal activity during a circumscribed period in development. Disrupting the activity of Y-cells (by dark rearing or by monocular lid suture) or of motor neurons (by sciatic nerve crush or by spinal cord lesion) during the early postnatal period prevents Cat-301 expression. Disrupting neuronal activity in adults has no effect on Cat-301 expression. The onset of Cat-301 expression corresponds to the end of the period of activity-dependent development. In order to further dissect the components of the segmental reflex are required for the expression of Cat-301 on motor neurons, here we evaluated the effect of deafferentation by dorsal rhizotomy. In adult animals two weeks after deafferentation all sciatic motor neurons continue to express Cat-301. In contrast, in neonates two weeks after deafferentation the normal developmental expression of Cat-301 is reduced and less than 50% of sciatic motor neurons express Cat-301. We next selectively lesioned the small diameter afferents using the neurotoxin capsaicin. In contrast to rhizotomy, neonatal deletion of small diameter afferents has no effect on the development of Cat-301 expression on motor neurons. These results imply that input relayed by large diameter primary afferents (probably those conveying muscle and/or joint information) is required for normal maturation of motor neuronal properties during early life. They also provide further evidence for activity-dependent maturation of motor neurons.
authors.affiliation: Section of Neuroanatomy, Yale University School of Medicine, New Haven, CT 06510.
authors.forename: R G
authors.initials: RG
authors.lastname: Kalb
authors.forename: S
authors.initials: S
authors.lastname: Hockfield
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D006224:Cricetinae; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000378:metabolism*; D008647:Mesocricetus / Q000378:metabolism / Q000502:physiology; D009046:Motor Neurons / Q000378:metabolism* / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology*; D011509:Proteoglycans / Q000378:metabolism*; D012584:Sciatic Nerve / Q000378:metabolism / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*
chemical_list: D000911:Antibodies, Monoclonal; D008565:Membrane Proteins; D011509:Proteoglycans; D015740:Calcitonin Gene-Related Peptide