The superimposed effects of chronic phrenicotomy and cervical spinal cord hemisection on synaptic cytoarchitecture in the rat phrenic nucleus.
The present study was carried out to determine the effects of a combined peripheral phrenicotomy and rostral spinal cord hemisection on the synaptic architecture in the ipsilateral rat phrenic nucleus. Young adult female Sprague-Dawley rats were divided into a hemisection-alone and two hemisection-plus-phrenicotomy (HPP) groups. In all animals, DiI, a fluorescent carbocyanine dye was injected into the left hemidiaphragm to retrogradely label the ipsilateral phrenic motoneurons. In the HPP groups, left intrathoracic phrenicotomies were carried out at 2 and 4 weeks prior to sacrificing. Hemisection-alone animals were not subjected to phrenicotomy. In all animals, a left C2 spinal cord hemisection was performed 24 h prior to death. Quantitative morphometric analysis of the phrenic nucleus showed that the number of synapses contacting phrenic profiles is significantly less in the HPP (2 week) group as compared to the hemisection-alone group, but this number returns to a level not significantly different from the hemisection-alone value in the HPP (4 week) group. The results suggest that the transient change in the number of synapses might contribute to the differential expression of the crossed phrenic phenomenon documented in another group of animals subjected to the same surgical procedures. Furthermore, the different stages of glial reaction induced by phrenicotomy/spinal cord hemisection might underlie the change in synaptic number.
Liou
W W
WW
Wayne State University, School of Medicine, Department of Anatomy and Cell Biology, Detroit, Michigan 48201, USA.
Goshgarian
H G
HG
D000818:Animals; D002232:Carbocyanines; D048429:Cell Size; D002908:Chronic Disease; D002818:Cordotomy; D003712:Dendrites / Q000502:physiology / Q000648:ultrastructure; D004594:Electrophysiology; D005260:Female; D005456:Fluorescent Dyes; D008854:Microscopy, Electron; D009046:Motor Neurons / Q000502:physiology / Q000648:ultrastructure; D009473:Neuronal Plasticity / Q000502:physiology; D010791:Phrenic Nerve / Q000166:cytology / Q000601:surgery*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure
C101089:CM-DiI; D002232:Carbocyanines; D005456:Fluorescent Dyes