Excitatory amino acid release in the locus coeruleus during naloxon-precipitated morphine withdrawal in adjuvant arthritic rats

Objective and Design: Excitatory amino acid levels in the locus coeruleus ( LC) and the behavioral signs during naloxone-precipitated withdrawal in art hritic rats treated with chronic morphine were investigated by in vivo micr odialysis. Methods: Increases in glutamate (Glu) and aspartate (Asp) were noted after naloxone (48 nmol/5 mu l, LC)-precipitated withdrawal from normal and adjuv ant arthritic rats which had been intracerebroventricularly infused for 3 d ays with morphine (26 nmol/l mu l/h). Results: The increases in Glu and Asp levels on morphine withdrawal in norm al rats were attenuated following naloxone challenge in the morphine-depend ent arthritic rats. Moreover, behavioral signs during morphine withdrawal w ere detected following the naloxone challenge in both the morphine-dependen t normal and adjuvant arthritic rats, but not in the saline-infused control s. Conclusions: These results show that the attenuation of Glu and Asp release from the LC in the adjuvant arthritic rats might explain the anti-inflamma tory and analgesic effects of mu-opioids in adjuvant arthritic rats.