The Related Factors of Neuropeptide Y in the Cuneate Nucleus and Dorsal Root Ganglion after Median Nerve Transection of Rats

• Main Authors: Yi-Ju Tsai, 蔡怡汝
• Other Authors: June-Horng Lue
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/95973364378438206609

博士 === 國立臺灣大學 === 解剖學研究所 === 93 === 英文摘要 Our previous study had revealed that the neuropeptide may contribute to nerve injury-induced hyperalgesia in rats’ forelimb of median nerve injury with special reference to neuropeptide Y (NPY). Although several studies has revealed that the increased NPY in the gracile nucleus and dorsal root ganglion (DRG) following sciatic nerve injury, and it still lacks confirmation in the cuneate nucleus (CN) and DRG after complete median nerve transection (CMNT). In the present proposal, we will use the median nerve injury animal models, immunocytochemistry, neuronal tracer labeling, dorsal rhizotomy, electrical stimulation, electromicroscopic, and pre-emptive drug treatment in anesthetized rats. First, we examined characteristics of the neuropeptide Y-like immunoreactive (NPY-LI) DRG neurons after CMNT. With Fluorogold (FG) injection into normal median nerves, numerous FG-labeled DRG neurons were predominantly localized in the C6 and C7 DRGs, where focal regions were examined after CMNT. Along with NPY immunohistochemistry, a few NPY-LI neurons were detected in the ipsilateral but not contralateral DRGs after FG injection into the nerve. As early as three days after CMNT a few NPY-LI neurons could be detected, reaching a maximum in the percentage of the NPY-LI neurons in the DRGs at four weeks, subsided thereafter over twenty weeks. The NPY-LI DRG neurons were primarily medium-sized and large neurons. With FG injection into the transected median nerve, we found that about 99% of NPY-LI neurons were labeled for FG, suggesting that they are derived from the injured but not intact DRG neurons. Then, using double fluorescent dyes tract tracing, we detected that some of the injured DRG neurons were NPY-LI neurons that projected to the CN. Further treated with dorsal rhizotomy, our data indicated that after CMNT the induced NPY-LI fibers in the ipsilateral CN were exclusively originated from the injured DRG neurons. Finally, we have used retrograde tract-tracing of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) and NPY immunohistochemistry labeling methods to clarify the synaptic relationships between cuneothalamic projection neurons (CTNs) and NPY-LI terminals in the CN of CMNT rats. Ultrastructurally, the NPY-LI terminals made asymmetric axodendritic synaptic contact with HRP-labeling CTN dendrites. Taken together, these findings suggest that injury-induced NPY-LI fibers in the CN may originate from the injured DRG neurons via the median nerve primary afferent fibers, affect the excitability of CTNs, and involve neuropathic sensation following CMNT. Then, four weeks after CMNT when given electrical stimulation, c-Fos-like immunoreactive (c-Fos-LI) cells (mean density = 60.1