SUPRASPINAL DELTA-OPIOID RECEPTOR MESSENGER-RNA LEVELS ARE NOT ALTERED IN [D-ALA(2)]DELTORPHIN-II TOLERANT MICE

Delta opioid receptor (DOR) mRNA levels were studied in mice rendered tolerant to [D-Ala(2)]deltorphin II by 4 days of repeated intracerebroventricular administration (10 mu g, [tid]). ED(50) determinations on day 5 revealed a 10-fold loss in [D-Ala(2)]deltorphin II potency with the tail-flick test, Utilization of a microdissection technique followed by quantitative solution hybridization of RNA extracts from mouse brain revealed mean levels of DOR mRNA ranging from 3.9 pg/mu g RNA in the caudate-putamen to 0.4 pg/mu g RNA in the cerebellum, DOR mRNA levels were not different when RNA extracts from tolerant and nontolerant mice were compared. These data suggest that altered DOR mRNA levels are not one of the adaptive changes that occur with delta opioid ([D-Ala(2)]deltorphin II) tolerance. (C) 1994 Wiley-Liss, Inc.