A model of chronic pain in the rat: response of multiple opioid systems to adjuvant-induced arthritis.
Chronic arthritic pain was induced by intradermally inoculating rats at the tail-base with Mycobacterium butyricum, which results in swelling, inflammation, and hyperalgesia of the joints. These symptoms peak at 3 weeks after inoculation and disappear by 10 weeks. The following changes were seen at 3 weeks. Immunoreactive dynorphin (ir-Dyn) and ir-alpha-neo-endorphin (alpha-NE) manifested comparable patterns of change. Their levels were increased in the anterior, but not neurointermediate, pituitary. The thalamus showed a rise in ir-Dyn and ir-alpha-NE, but no alterations were seen in other brain regions. In each case, cervical, thoracic, and lumbosacral sections of the spinal cord showed a rise in ir-Dyn and ir-alpha-NE: This was most pronounced in the lumbosacral region, where the magnitude of these shifts correlated with the intensity of arthritic symptoms. In addition, a moderate elevation in ir-methionine-enkephalin (ME) was seen in lumbosacral spinal cord. In brain, ir was not changed. The level of ir-beta-endorphin (beta-EP) was elevated both in the plasma and the anterior, but not the neurointermediate, pituitary. In addition, the content of messenger RNA encoding the beta-EP precursor, proopiomelanocortin (POMC), was enhanced in the anterior lobe. Thus, there was a selective activation of synthesis of beta-EP in, and its secretion from, the anterior lobe. In no brain tissue did levels of ir-beta-EP change. At 10 weeks postinoculation, the above changes were no longer apparent, indicating their reversibility.(ABSTRACT TRUNCATED AT 250 WORDS)
Millan
M J
MJ
Millan
M H
MH
Członkowski
A
A
Höllt
V
V
Pilcher
C W
CW
Herz
A
A
Colpaert
F C
FC
D000818:Animals; D001168:Arthritis / Q000378:metabolism*; D001169:Arthritis, Experimental / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D002908:Chronic Disease; D004174:Diprenorphine / Q000378:metabolism; D004195:Disease Models, Animal; D004399:Dynorphins / Q000032:analysis / Q000378:metabolism; D004723:Endorphins / Q000032:analysis / Q000378:metabolism* / Q000502:physiology; D007031:Hypothalamus / Q000032:analysis / Q000378:metabolism; D008297:Male; D008636:Mesencephalon / Q000032:analysis / Q000378:metabolism; D010146:Pain / Q000378:metabolism* / Q000503:physiopathology; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000032:analysis / Q000378:metabolism / Q000502:physiology; D013116:Spinal Cord / Q000378:metabolism*; D013788:Thalamus / Q000032:analysis / Q000378:metabolism; D001615:beta-Endorphin
D004723:Endorphins; D011957:Receptors, Opioid; D004174:Diprenorphine; D001615:beta-Endorphin; D004399:Dynorphins