Dorsal root ganglion neurons respond with prolonged extracellular signal-regulated protein kinase phosphorylation following noxious heat and cold stimulation.
In the present study the time course of extracellular signal-regulated protein kinase phosphorylation (pERK1/2 appearance) in lumbar sensory dorsal root ganglia (DRG) was determined following a 5-min noxious heat or a noxious cold stimulus to the hind paw of the rat. The thermal stimuli were chosen to activate transient receptor potential (TRP) channels, but not to induce tissue damage. A quantitative analysis of phospho-ERK1/2 was performed by protein extraction and Western blot analysis. Western blot analysis showed that following the heat stimulus, phosphorylation of ERK1/2 increased 2-3-fold between 10 and 30min in the DRG on the ipsilateral side. High levels were maintained from 30min up to 16h. Following the cold stimulus to the paw, pERK1/2 immediately increased 2-fold within 2min in the DRG on the ipsilateral side, it declined within 2h and reached a second peak at 4h. In the DRGs on the contralateral side of the paw's heat or cold immersion the pERK1/2 remained low at all time points investigated. Fluorescence immunohistochemistry of the DRG following the thermal stimuli revealed an increased cytoplasmic staining for pERK1/2 in neurons. The present results show that following a 5-min nociceptive thermal stimulus sensory neurons respond with a characteristic long-lasting phosphorylation of ERK1/2.
Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria. josef.donnerer@medunigraz.at
Josef
J
Donnerer
Ingrid
I
Liebmann
D000818:Animals; D003080:Cold Temperature; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism*; D006358:Hot Temperature; D008161:Lumbosacral Region; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D011984:Sensory Receptor Cells / Q000378:metabolism*
D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3