title: pERK1/2 immunofluorescence in rat dorsal horn and paraventricular nucleus neurons as a marker for sensitization and inhibition in the pain pathway.
abstract: The aim of the present study was to investigate whether the phosphorylation of ERK1/2 in the rat lumbar dorsal horn and in the parvocellularis part of the paraventricular nucleus can be used to visualize neuronal activity. pERK1/2 fluorescence-immunohistochemistry is specifically suited to mirror neuronal activity in the pain pathway following an acute noxious stimulation. The rat hind paw was either stimulated by noxious heat or by a sequence of mustard oil and noxious heat. Two and 10 min after the thermal stimulation a 3-4-fold increase in cells with pERK1/2 immunoreactivity was observed in lamina I/II of the L3-L5 dorsal horn. The combination of mustard oil with heat led to a 5-6-fold increase in the pERK1/2 signal. The pERK1/2 immunoreactivity in the parvocellularis part of the paraventricular nucleus increased by 2-fold following the heat stimulus, with no further increase following the sequential mustard oil and heat stimulus. A pretreatment with the opioid analgesic morphine or the NMDA antagonist MK-801 markedly attenuated ERK1/2 phosphorylation in both areas of the pain pathway. The present findings support the concept that the pERK1/2 immunofluorescence signal can be used as a quantitative marker for sensitization or inhibition in the pain pathway at spinal and hypothalamic level.
authors.affiliation: Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria. Electronic address: josef.donnerer@medunigraz.at.
authors.forename: J
authors.initials: J
authors.lastname: Donnerer
authors.affiliation: Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria.
authors.forename: I
authors.initials: I
authors.lastname: Liebmann
mesh_terms: D000818:Animals; D005455:Fluorescent Antibody Technique; D006358:Hot Temperature; D008297:Male; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009020:Morphine / Q000008:administration & dosage; D009149:Mustard Plant / Q000633:toxicity; D009474:Neurons / Q000201:enzymology* / Q000473:pathology; D010146:Pain / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology; D010286:Paraventricular Hypothalamic Nucleus / Q000201:enzymology* / Q000473:pathology; D010766:Phosphorylation; D010938:Plant Oils / Q000633:toxicity; D051381:Rats; D017207:Rats, Sprague-Dawley; D066148:Spinal Cord Dorsal Horn / Q000201:enzymology* / Q000473:pathology
chemical_list: D010938:Plant Oils; D009020:Morphine; D048052:Mitogen-Activated Protein Kinase 3; C027793:mustard oil
keywords: ERK1/2 phosphorylation; Hypothalamus; NMDA antagonist; Nociception; Opioid analgesic; Spinal cord