title: Morphine withdrawal modifies antinociceptive effects of acute morphine in rats.
abstract: Repeated opioid use is known to cause tolerance of antinociceptive effects. Whether opioid abstinence modifies antinociceptive effects is unknown. Here we reported that morphine withdrawal for 18 h and 4 days after repeated morphine treatment largely reduced tail-flick latencies compared with control, while the rats showed severe withdrawal syndromes. However, the latencies and withdrawal syndromes were restored to control level at 20 days withdrawal. Similarly, antinociceptive effects of acute morphine were decreased at 18 h and further decreased at 4 days but restored to control level at 20 days withdrawal. Behavioral stress that was given to the rats at 18 h withdrawal further reduced tail-flick latencies and antinociceptive effects. Conversely, the glucocorticoid receptor antagonist RU38486 increased tail-flick latencies and antinociceptive effects at 4 days withdrawal. These results suggest that morphine withdrawal could evoke behavioral stress to modify antinociceptive effects, implicating a significant influence of opioid abstinence on chronic pain treatment.
authors.affiliation: Key Laboratory of Animal Models and Human Disease Mechanisms, and Laboratory of Learning and Memory, Kunming Institute of Zoology, The Chinese Academy of Sciences, Kunming, PR China.
authors.forename: Zhifang
authors.initials: Z
authors.lastname: Dong
authors.forename: Rongrong
authors.initials: R
authors.lastname: Mao
authors.forename: Huili
authors.initials: H
authors.lastname: Han
authors.forename: Jun
authors.initials: J
authors.lastname: Cao
authors.forename: Lin
authors.initials: L
authors.lastname: Xu
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004361:Drug Tolerance; D008297:Male; D015735:Mifepristone / Q000494:pharmacology; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009021:Morphine Dependence / Q000503:physiopathology*; D010146:Pain / Q000188:drug therapy / Q000503:physiopathology*; D010147:Pain Measurement; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors / Q000502:physiology; D013315:Stress, Psychological / Q000503:physiopathology; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology*
chemical_list: D000701:Analgesics, Opioid; D011965:Receptors, Glucocorticoid; D015735:Mifepristone; D009020:Morphine