A time course analysis of the changes in neuropeptide Y immunoreactivity in the rat cuneate nucleus following median nerve transection.
Using median nerve injury and immunocytochemical methods, we examined the temporal changes in neuropeptide Y (NPY) expression in the cuneate nucleus (CN) in rats following median nerve transection. Under normal circumstances, neuropeptide Y-immunoreactive (NPY-IR) fibers was not detectable in the CN. A few NPY-IR fibers were observed in the ipsilateral CN 5 days after the median nerve transection, and peaked at 4 weeks. Thereafter, they were gradually returned to nearly control level after 16 weeks. Quantitative evaluation showed that the mean percentage of area occupied by NPY-IR fibers in entire and three subregions of the CN at 4 weeks were significantly higher than that at other post-operated time points, respectively. The present ultrastructural observations in the middle region of CN showed that the significantly increased NPY immunoreactivity was confined only in the myelinated axons and terminals but not detected in the dendrites, somata, and glial cells. The NPY-IR terminals made axodendritic synaptic contacts with unlabeled elements. The present results indicate that the time course of the increase of NPY immunoreactivity is similar to c-Fos expression as described in a previous study. It is speculated that the increased NPY in the CN after axotomy may affect the excitability of postsynaptic cuneate neurons, however, the functional interaction between NPY and c-Fos-IR neurons needs to be further studied.
Tsai
Yi-Ju
YJ
Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei 10018, Taiwan, ROC.
Leong
Sok-Man
SM
Day
An-Shiou
AS
Wen
Chen-Yuan
CY
Shieh
Jeng-Yung
JY
Lue
June-Horng
JH
D000818:Animals; D019771:Axotomy; D001921:Brain / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008854:Microscopy, Electron; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure*; D009478:Neuropeptide Y / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D009478:Neuropeptide Y