Dependence and withdrawal following intracerebroventricular and systemic morphine administration: functional anatomy...

Regional cerebral glucose utilization (RCGU) and behavior during precipitated morphine withdrawal were studied in rats made dependent by either intracerebroventricular (i.c.v.) or subcutaneous (s.c.) administration of morphine. [14C]2-deoxy-D-glucose autoradiography revealed that RCGU increased in an anatomically related group of limbic and brainstem structures in rats that were in morphine withdrawal precipitated by naloxone administration compared to morphine-dependent controls that were not in precipitated withdrawal. Correlation of RCGU for 24 brain structures comparing i.c.v. vs s.c. morphine-treated rats was highly significant for groups in withdrawal and for controls (r values, 0.958 and 0.971, respectively). Withdrawal behaviors including autonomic signs of withdrawal, withdrawal jumping, and incidence of diarrhea were not different between the two groups in withdrawal (i.c.v. and s.c.). Weight loss during withdrawal increased (P less than 0.05) in rats made dependent by s.c. morphine administration compared to rats that received morphine by the i.c.v. route. Taken together, these results indicate that RCGU changes during morphine withdrawal result solely from effects of chronic morphine in the central nervous system, not in peripheral sites. The increased weight loss of s.c.-treated, morphine-dependent rats in withdrawal suggests an independent peripheral effect perhaps mediated by visceral opiate receptors.