title: Chronopharmacology of morphine in mice.
abstract: Dosing-time-dependent changes in the effect and toxicity of morphine were examined in mice housed under alternating 12 h light (07:00 to 19:00 h) and dark (19:00 to 07:00 h) cycles. Morphine (0.5 mg/kg) was injected intraperitoneally (i.p.) in animals to assess its beneficial effect (i.e., protection against the kaolin-induced, bradykinin-mediated, writhing reaction) and its toxicity (i.e., alteration of the hepatic enzymes of aspartate aminotransferase [AST] alanine aminotransferase [ALT], and glutathione [GSH] in separate experiments). The magnitude of the analgesic effect of morphine depended on dosing time, with minimum effect at 02:00 h and maximum effect at 14:00 h. The serum hepatic enzyme levels of AST and ALT increased after dosing morphine (100 mg/kg) at 02:00 and 14:00 h. Time courses of these enzymes did not differ between the two trials. However, hepatic GSH, which is involved in the detoxification of chemical compounds, significantly decreased after i.p. morphine injection at 02:00 but not at 14:00 h. Overall, the results suggest that the analgesic effect of morphine is greater after dosing during the resting than during the activity phase of mice that have been induced with bradykinin-mediated pain. Drug-induced hepatic damage as inferred by GSH alteration, however, may be greater after dosing during the active phase.
authors.affiliation: Department of Clinical Pharmacology, Jichi Medical School, Tochigi, Japan.
authors.forename: Yimin
authors.initials: Y
authors.lastname: Cui
authors.forename: Koh-ichi
authors.initials: K
authors.lastname: Sugimoto
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Araki
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sudoh
authors.forename: Akio
authors.initials: A
authors.lastname: Fujimura
mesh_terms: D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D000930:Antidiarrheals / Q000008:administration & dosage; D001219:Aspartate Aminotransferases / Q000097:blood; D002940:Circadian Rhythm / Q000502:physiology*; D005978:Glutathione / Q000378:metabolism; D007616:Kaolin / Q000008:administration & dosage; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D008297:Male; D051379:Mice; D009020:Morphine / Q000378:metabolism* / Q000627:therapeutic use / Q000633:toxicity; D009294:Narcotics / Q000378:metabolism* / Q000627:therapeutic use / Q000633:toxicity; D010146:Pain / Q000139:chemically induced / Q000188:drug therapy; D017440:Photoperiod; D013997:Time Factors
chemical_list: D000930:Antidiarrheals; D009294:Narcotics; D007616:Kaolin; D009020:Morphine; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D005978:Glutathione