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Depression of Ca 2+ /calmodulin‐dependent protein kinase II in dorsal root ganglion neurons after spinal nerve ligation
Author(s) -
Kojundzic Sanja Lovric,
Puljak Livia,
Hogan Quinn,
Sapunar Damir
Publication year - 2009
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.22209
Subject(s) - axotomy , dorsal root ganglion , protein kinase a , chemistry , medicine , calmodulin , neuropathic pain , peripheral nerve injury , phosphorylation , endocrinology , spinal cord , neuroscience , calcium , biology , central nervous system , biochemistry , sciatic nerve
The enzyme calcium/calmodulin‐dependent protein kinase II (CaMKII) is associated with memory and its α isoform is critical for development of activity‐induced synaptic changes. Therefore, we hypothesized that CaMKII is involved in altered function of dorsal root ganglion (DRG) neurons after neuronal injury. To test this hypothesis, Sprague–Dawley rats were made hyperalgesic by L5 and L6 spinal nerve ligation (SNL), and changes in total phosphorylated and unphosphorylated CaMKII (tCaMKII) and phosphorylated form of its α isoform (pCaMKIIα) were analyzed using immunochemistry in different subpopulations of DRG. SNL did not induce any changes in tCaMKII between experimental groups, while the overall percentage of pCaMKIIα‐positive neurons in injured L5 DRG SNL (24.8%) decreased significantly when compared to control (41.7%). SNL did not change the percentage of pCaMKIIα/N52 colabeled neurons but decreased the percentage of N52‐negative nonmyelinated neurons that expressed pCaMKIIα from 27% in control animals to 11% after axotomy. We also observed a significant decrease in the percentage of small nonpeptidergic neurons labeled with IB4 (37.6% in control vs. 4.0% in L5 SNL DRG), as well as a decrease in the percentage of pCaMKIIα/IB4 colabeled neurons in injured L5 DRGs (27% in control vs. 1% in L5 DRG of SNL group). Our results show that reduction in pCaMKIIα levels following peripheral injury is due to the loss of IB4‐positive neurons. These results indicate that diminished afferent activity after axotomy may lead to decreased phosphorylation of CaMKIIα. J. Comp. Neurol. 518:64–74, 2010. © 2009 Wiley‐Liss, Inc.