Excitatory amino acid release in the locus coeruleus during naloxone-precipitated morphine withdrawal in adjuvant arthritic rats.
OBJECTIVE
Excitatory amino acid levels in the locus coeruleus (LC) and the behavioral signs during naloxone-precipitated withdrawal in arthritic rats treated with chronic morphine were investigated by in vivo microdialysis.


METHODS
Increases in glutamate (Glu) and aspartate (Asp) were noted after naloxone (48 nmol/5 microl, LC)-precipitated withdrawal from normal and adjuvant arthritic rats which had been intracerebroventricularly infused for 3 days with morphine (26 nmol/l microl/h).


RESULTS
The increases in Glu and Asp levels on morphine withdrawal in normal rats were attenuated following naloxone challenge in the morphine-dependent arthritic rats. Moreover, behavioral signs during morphine withdrawal were detected following the naloxone challenge in both the morphine-dependent normal and adjuvant arthritic rats, but not in the saline-infused controls.


CONCLUSIONS
These results show that the attenuation of Glu and Asp release from the LC in the adjuvant arthritic rats might explain the anti-inflammatory and analgesic effects of mu-opioids in adjuvant arthritic rats.
Hoshi
K
K
Department of Pharmacology, Hokkaido College of Pharmacy, Otaru, Japan. khoshi@hucc.hokudai.ac.jp
Yamamoto
A
A
Ishizuki
S
S
Fujihira
E
E
Ichihara
K
K
D000818:Animals; D001169:Arthritis, Experimental / Q000188:drug therapy / Q000503:physiopathology*; D001522:Behavior, Animal; D018846:Excitatory Amino Acids / Q000378:metabolism*; D008125:Locus Coeruleus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009020:Morphine / Q000008:administration & dosage* / Q000627:therapeutic use; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D009293:Opioid-Related Disorders; D051381:Rats; D017207:Rats, Sprague-Dawley; D013375:Substance Withdrawal Syndrome
D018846:Excitatory Amino Acids; D009292:Narcotic Antagonists; D009270:Naloxone; D009020:Morphine