Synaptophysin (SYP) plays an important role in synaptogenesis and synaptic transmission of nerve impulses, regulates exo- and endocytosis of synaptic vesicles. SYP is most widely used as a immunohistological marker for determining the synaptic densities, and it is used as a marker of neuronal differentiation. The aim of this work is to study the development of synaptophysin-containing rat dorsal root ganglion cells of embryos and newborn rats using immunohistochemistry.
Wistar rat embryos 12,14,15,17,19 days of gestutional age (n=23) and newborn rats (n=5) were used in this study. SYP-immunopositive cells were not found between 12 to17 embryonic days. Single cells containing SYP were determined in rat dorsal root ganglia at 19 embryonic day. Staining was detected in the perinuclear region. At this period of embryonic development synaptophysin was detected primarily in large dorsal root ganglion cells and only some of small cells were SYP-immunopositive. Number of neurons containing synaptophysin were increased at newborn rats: SYP-immunopositive staining were observed in bodies of large and small neurons of spinal ganglia. Some sensory neurons were SYP-immunonegative.
In the early stages of embryonic development SYP-immunopositive cells were not found in rat dorsal root gangla because in this period the axons of ganglion cells only penetrate into posterior horns of the spinal cord, but synaptic contacts have not yet formed. From the 19th day of embryonic development the accumulation of synaptophysin in rat dorsal root ganglion cells is associated with synaptogenesis. It was during this period contacts between processes of sensory ganglion cells and neurons of rat spinal cord are formed.