title: Tolerance to opioids in single locus coeruleus neurons of the rat.
abstract: Chronic treatment of rats with morphine caused tolerance to the membrane hyperpolarizing action of morphine in single locus coeruleus neurons in vitro. Tolerance was less pronounced for Try-D-Ala-Gly-MePhe-Gly-ol (DAGO) than for normorphine. No changes were found in affinity of naloxone for mu-receptors on these neurons, nor in the properties of the potassium conductance increase caused by mu-receptor activation. These results suggest that the mechanisms underlying tolerance involve either a reduction of the number of mu-receptors on each cell, or a reduced coupling of mu-receptors to potassium channels.
mesh_terms: D000818:Animals; D004361:Drug Tolerance; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000494:pharmacology*; D066298:In Vitro Techniques; D008125:Locus Coeruleus / Q000187:drug effects / Q000502:physiology*; D009020:Morphine / Q000494:pharmacology*; D009022:Morphine Derivatives / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats
chemical_list: D004745:Enkephalins; D009022:Morphine Derivatives; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009020:Morphine; C010616:normorphine