Cerebral glucose metabolism during opioid withdrawal following methylnaloxonium injection into the locus coeruleus

Previous studies have demonstrated a widespread stimulation of regional cer ebral metabolic rate(s) for glucose (rCMRglc) in morphine-dependent rats su bjected to opioid withdrawal precipitated by systemic injection of naloxone . Nonetheless, many of the behavioral signs of opioid withdrawal are produc ed by intracerebral injections of an opioid antagonist, methylnaloxonium (M N), into the locus coeruleus (LC). The purpose of the present work was to d etermine the extent to which cerebral metabolic alterations in opioid withd rawal could be initiated by a local action in LC, Intracerebral injections of MN into LC increased rCMRglc in morphine-dependent rats, and the anatomi cal distribution of this effect was similar to that produced by systemic in jections of naloxone. The present data support the view that LC is a major substrate of opioid withdrawal in the brain, and they suggest that LC plays an important role in changing rCMRglc during opioid withdrawal induced by systemic naloxone administration. (C) 1998 Elsevier Science B.V. All rights reserved.