Rats treated chronically with morphine were found to have an increased number of mu-noncompetitive delta binding sites. The increase in the Bmax was 39% and the enhancement was blocked by pre-incubation in 50 mM Tris, pH 7.4 with 400 mM NaCl for one hour at 25 degrees C. These findings are consistent with the removal of newly manifested binding sites being a specific property of sodium, by analogy with previous studies where sodium has been shown to extract extrinsic proteins from red cell ghosts.
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Differential coupling of mu-competitive and mu-noncompetitive delta opiate receptors to guanine nucleotide binding proteins in rat brain membranes.
Biochem Pharmacol
February 1988
Division of Biology and Medicine, Brown University, Providence, RI 02912.
The effects of fentanyl isothiocyanate (FIT) and pertussis toxin on the binding of [3H]D-Ala2, D-Leu5-enkephalin ([3H]DADLE) to rat brain membranes were compared. The site of action of pertussis toxin was confirmed by the labeling of a 41,000 dalton protein in the presence of [alpha-32P]NAD. Both reagents produced inhibition of [3H]DADLE binding when binding was assayed in 10 mM Tris-HCl buffer alone.
View Article and Find Full Text PDFIn light of more recent knowledge concerning endogenous opioid peptides and their multiple opiate receptors, we reevaluated the effects of morphine tolerance on opiate receptor binding parameters. Rats were implanted with morphine or placebo pellets, and [3H][D-Ala2,D-Leu5]enkephalin ([3H]DADL) was used to label brain membranes. Utilizing the technique of binding surface analysis, we observed a selective 47% up-regulation of lower affinity [3H]DADL binding sites (mu-noncompetitive delta binding sites) in morphine pelleted rats.
View Article and Find Full Text PDFUpregulation of the mu-noncompetitive delta binding site by chronic morphine administration: effect of preincubating membranes in 400 nM sodium chloride.
NIDA Res Monogr
March 1988
Laboratory of Preclinical Pharmacology, St. Elizabeth's Hospital, NIMH, Washington, DC 20032.
Rats treated chronically with morphine were found to have an increased number of mu-noncompetitive delta binding sites. The increase in the Bmax was 39% and the enhancement was blocked by pre-incubation in 50 mM Tris, pH 7.4 with 400 mM NaCl for one hour at 25 degrees C.
View Article and Find Full Text PDFConsiderable evidence supports the notion that the prototypic delta agonist [3H]D-ala2-D-leu5-enkephalin labels two binding sites on brain membranes in vitro. Recent studies have demonstrated that treatment of brain membranes with the delta-selective, site-directed, alkylating agent, FIT (Rice et al., Science 220, 314-316, 1983) results in a membrane preparation devoid of detectable higher affinity [3H]D-ala2-D-leu5-enkephalin binding sites, but contain residual lower affinity binding sites at which mu-ligands are apparent noncompetitive inhibitors (Rothman et al.
View Article and Find Full Text PDFThe mechanism by which mu ligands inhibit the binding of prototypic delta agonists to preparations of brain membranes is controversial. Most investigators assume competitive inhibition. In this study, we examine the interaction of the mu agonist oxymorphone and delta agonist DSTLE (D-Ser2-Thr6-Leu-enkephalin) with [3H]D-Ala2-D-Leu5-enkephalin (DADL) binding to membranes of rat brain.
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