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 intracerebro ventricular 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 follow ed by quantitative solution hybridization of RNA extracts from mouse b rain 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 lev els were not different when RNA extracts from tolerant and nontolerant mice were compared. These data suggest that altered DOR mRNA levels a re not one of the adaptive changes that occur with delta opioid ([D-Al a(2)]deltorphin II) tolerance. (C) 1994 Wiley-Liss, Inc.