title: Alteration in endogenous opioid systems due to chronic inflammatory pain conditions.
abstract: The influence of chronic arthritic pain on two endogenous opioid peptides, dynorphin B and [Met5]enkephalin-Arg6-Phe7, and multiple opioid receptors in discrete brain, lumbar spinal cord and pituitary pools was investigated. Using radioimmunoassay and receptor binding assay, we examined the changes in regional opioid peptide levels and opioid receptor activity due to chronic inflammation in adjuvant arthritic rats. At 4 weeks post-inoculation, increased levels of immunoreactive dynorphin B and [Met5]enkephalin-Arg6-Phe7 were measured in tissues of arthritic rats compared with controls. No significant changes in mu-, delta- or kappa-opioid receptors were seen after chronic inflammation. Taken together, these results indicate that in chronic arthritis, opioid receptor changes do not follow the peptide alterations of pro-dynorphin and pro-enkephalin systems. Thus, dynamic modification and modulation of nociceptive information takes place during chronic inflammation. This supports the key role of the central nervous system in chronic inflammatory pain conditions.
authors.affiliation: Section of Orthopaedics, Department of Surgical Sciences, Karolinska Institute, Orthopaedic Research Laboratory M3:02, Karolinska Hospital, S-171 76, Stockholm, Sweden. Mariana.Spetea@uibk.ac.at
authors.forename: Mariana
authors.initials: M
authors.lastname: Spetea
authors.forename: Gustav
authors.initials: G
authors.lastname: Rydelius
authors.forename: Ingrid
authors.initials: I
authors.lastname: Nylander
authors.forename: Mahmood
authors.initials: M
authors.lastname: Ahmed
authors.forename: Indre
authors.initials: I
authors.lastname: Bileviciute-Ljungar
authors.forename: Thomas
authors.initials: T
authors.lastname: Lundeberg
authors.forename: Stefan
authors.initials: S
authors.lastname: Svensson
authors.forename: Andris
authors.initials: A
authors.lastname: Kreicbergs
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002908:Chronic Disease; D004195:Disease Models, Animal; D004399:Dynorphins / Q000378:metabolism; D004723:Endorphins / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000378:metabolism; D005260:Female; D007249:Inflammation / Q000209:etiology; D018847:Opioid Peptides / Q000378:metabolism*; D010146:Pain / Q000139:chemically induced / Q000378:metabolism*; D010147:Pain Measurement; D051381:Rats; D011917:Rats, Inbred Lew; D011957:Receptors, Opioid / Q000378:metabolism*; D013116:Spinal Cord / Q000378:metabolism
chemical_list: D004723:Endorphins; D018847:Opioid Peptides; D011957:Receptors, Opioid; D004744:Enkephalin, Methionine; D004399:Dynorphins; C036200:rimorphin