IS MORPHINE-DEPENDENCE MEDIATED EXCLUSIVELY BY THE MU RECEPTOR

Regional cerebral glucose utilization (RCGU) and behavior during nalox one precipitated withdrawal were studied in rats made dependent on eit her sufentanil, a highly selective mu opiate agonist, or morphine. Cha nges in RCGU during withdrawal in 23 of 24 anatomically related limbic and brainstem structures were indistinguishable between rats dependen t on morphine or sufentanil. Linear regression analysis indicated that RCGU changes during withdrawal in these two groups were highly correl ated (r=0.95). Withdrawal behaviors (autonomic sips of withdrawal, jum ps, weight loss, and incidence of diarrhea) were likewise indistinguis hable between the two groups. The correlations of both these measureme nts of dependence suggest that chronic occupation of mu opiate recepto rs alone is sufficient to produce dependence that is indistinguishable from morphine dependence.