title: The role of mu1 receptor in physical dependence on morphine using the mu receptor deficient CXBK mouse.
abstract: It is known that the CXBK inbred strain of mouse is deficient in mu1 opioid receptors, whereas the strain has a delta opioid receptor population that is less consistently altered. In the present study, we compared physical dependence on morphine between CXBK and C57BL/6 mice. Both strains of mice were treated with morphine-admixed food for 5 days. During the treatment, the two strains of mice showed no signs of toxicity. There was no significant difference in morphine intake during the treatment between CXBK and C57BL/6 mice. After the treatment, the withdrawal was precipitated by injecting naloxone (0.01-30 mg/kg, s.c.). CXBK mice showed weight loss, diarrhea and ptosis, but not jumping and body shakes after low dose of naloxone. Whereas, C57BL/6 mice showed weight loss, diarrhea, ptosis, body shakes and jumping. These results suggest that naloxone-precipitated weight loss, diarrhea and ptosis may be mediated by mu2 and/or delta opioid receptor, while naloxone-precipitated jumping and body shakes may be mediated by mu1 opioid receptors.
authors.affiliation: Department of Applied Pharmacology, School of Pharmacy, Hoshi University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
authors.forename: Y
authors.initials: Y
authors.lastname: Hayashi
authors.forename: M
authors.initials: M
authors.lastname: Misawa
mesh_terms: D000818:Animals; D001763:Blepharoptosis / Q000139:chemically induced; D003967:Diarrhea / Q000139:chemically induced; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D009021:Morphine Dependence / Q000503:physiopathology*; D009043:Motor Activity / Q000187:drug effects; D009270:Naloxone / Q000009:adverse effects; D011957:Receptors, Opioid / Q000502:physiology*; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D013375:Substance Withdrawal Syndrome / Q000209:etiology; D015431:Weight Loss
chemical_list: D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D009270:Naloxone