Immunolocalization and quantitation of a novel nerve terminal protein in spinal cord development

Abstract

In the adult spinal cord, the neuron-specific protein NT75 is located in nerve terminals synapsing in the superficial laminae of the dorsal horn. The present study examines the occurrence of NT75 in the developing rat spinal cord. NT75 immunoreactivity is detectable in primary afferent axons at the dorsal root entry zone on embryonic day 15. Subsequently, staining of presumptive nerve terminals appears in the deeper laminae of the dorsal horn, expanding into the superficial laminae during the first postnatal week. NT75 staining also appears in developing corticospinal tract axons in the brainstem at birth, and at lumbosacral levels by postnatal day 5. As NT75-positive nerve terminals approach the adult distribution, staining of primary afferent and corticospinal axons decreases, becoming undetectable by postnatal day 30. Dense transient staining of presumed nerve terminals in the ventral horn is also apparent during early postnatal development. Quantitative analysis of developing spinal cord shows a low level of NT75 immunoreactivity at birth. NT75 activity then increases substantially, reaching values by the third and fourth postnatal weeks up to 2.5 times that seen in adults. The occurrence of NT75 immunoreactivity correlates with the reported time course of synaptic development in the spinal cord. In addition, the results suggest that NT75 immunoreactivity is maintained at high levels in the nerve terminals of certain neural pathways into adulthood, whereas in other systems NT75 immunoreactivity may be detectable only during development.

Spatiotemporal distribution of neuronal calcium sensor‐1 in the developing rat spinal cord

“…The number of synapses in the molecular layer of the rat parietal cortex (Aghajanian and Bloom, 1967), motor-sensory cortex (Markus and Petit, 1987), and barrel field cortex (Micheva and Beaulieu, 1996) increases greatly during the second to the third postnatal week and reaches a maximum at P30. The number of synapses in the ventral horn of the rat spinal cord reaches adult level at P28 to P35 (Miki, 1995), and the nerve terminal protein NT75 and synaptophysin increase gradually during the first postnatal week and rapidly during the second to the third postnatal week and reaches a peak at P30 in the rat spinal cord (Cabalka et al, 1990). These previous studies support the idea that synaptogenesis may be completed until the end of fourth postnatal week during development of the rat CNS.…”

Efficacy of Single and Multiple Injections of Human Umbilical Tissue-Derived Cells following Experimental Stroke in Rats

“…Synaptophysin is used to quantify numbers of terminals during neuroanatomical remodeling and neural development [42]–[45].…”

Postnatal changes in responses of rat dorsal horn cells to afferent stimulation: a fibre‐induced sensitization

“…While the maturation of motoneurones, intermediate neurones and deep dorsal horn projection neurones is well underway, the superficial neurones of substantia gelatinosa (SG) are born late in fetal life and their axodendritic growth only begins postnatally (Altman & Bayer, 1984). Synaptogenesis in the cord peaks in the first 2 postnatal weeks and is concentrated in the deep dorsal horn at P4‐5 and in SG at P7‐9 (Cabalka, Ritchie & Coulter, 1990). The large, future‐myelinated, cutaneous afferents begin to enter the lumbar spinal cord at E15 (Fitzgerald et al 1991; Mirnics & Koerber, 1995), but C fibre afferents grow into the spinal cord only a few days before birth, at E18‐19, and the formation of C fibre synaptic connections is almost entirely a postnatal event (Fitzgerald, 1987 b ; Pignatelli, Ribeiro da Silva & Coimbra, 1989).…”