Morphine acts via mu-opioid receptors to enhance spinal regeneration and synaptic reconstruction of primary afferent fibers injured by sciatic nerve crush.
The present study investigated whether morphine can promote regeneration and synaptic reconstruction of the terminals of injured primary afferent fibers in lamina II of the spinal cord in rats following sciatic nerve injury. Fluoride-resistant acid phosphatase (FRAP)-positive terminals in lamina II of the L4 spinal segment after sciatic nerve injury were assessed after treatment with vehicle, morphine, and naloxone plus morphine. Under the electron microscope, types I and II complex terminals of unmyelinated afferent fibers from the dorsal root, simple terminals of interneuronal axons, and terminals of descending axons at lamina II of the L4 spinal segment were documented in the different groups after injury. FRAP-positive terminals in lamina II were depleted after sciatic nerve injury in the vehicle group. Treatment with morphine increased the numbers of FRAP-positive terminals, and this was prevented by naloxone. The present study demonstrates that morphine may promote the regeneration and synaptic reconstruction of the terminals of injured primary unmyelinated afferent fibers in lamina II of spinal cord, by a process mediated by mu-opioid receptors.
Zeng
Yuan-Shan
YS
Division of Neuroscience, Department of Histology and Embryology, Zhongshan Medical College, Sun Yat-Sen University, Guangzhou, China.
Nie
Jun-Hui
JH
Zhang
Wei
W
Chen
Sui-Jun
SJ
Wu
Wutian
W
D000135:Acid Phosphatase / Q000378:metabolism; D000344:Afferent Pathways / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D008297:Male; D009020:Morphine / Q000378:metabolism*; D009409:Nerve Crush; D036421:Nerve Fibers, Unmyelinated / Q000187:drug effects / Q000378:metabolism; D009416:Nerve Regeneration / Q000187:drug effects* / Q000502:physiology; D018696:Neuroprotective Agents / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000378:metabolism*; D012584:Sciatic Nerve / Q000166:cytology / Q000293:injuries / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D013569:Synapses / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure*; D058570:TOR Serine-Threonine Kinases
D018696:Neuroprotective Agents; D017450:Receptors, Opioid, mu; D009020:Morphine; D011494:Protein Kinases; D058570:TOR Serine-Threonine Kinases; D000135:Acid Phosphatase