%0 Journal Article %A Vu C. Dang %A John T. Williams %T Morphine-Induced μ-Opioid Receptor Desensitization %D 2005 %R 10.1124/mol.105.013185 %J Molecular Pharmacology %P 1127-1132 %V 68 %N 4 %X Morphine has been widely accepted as the opioid agonist that sustains signaling because it does not cause receptor desensitization or internalization. This notion has led to the hypothesis that long-term morphine treatment initiates downstream adaptations that underlie tolerance and dependence. This study uses whole-cell recordings from neurons in the locus ceruleus to measure the potassium current induced by morphine. The results show that morphine does cause short-term desensitization. The desensitization induced by morphine was slower and smaller then that induced by [MET]5-enkephalin (ME). After a brief application of a saturating concentration of ME, the current induced by morphine was smaller, and desensitization was not observed. In tissue taken from morphine-treated animals, the peak current induced by morphine was the same as in untreated animals, but morphine-induced desensitization was facilitated. The results suggest that morphine, like other agonists, can initiate receptor desensitization to decrease signaling. %U https://molpharm.aspetjournals.org/content/molpharm/68/4/1127.full.pdf