The role of the mu 2-opioid receptor in the antitussive effect of morphine in mu 1-opioid receptor-deficient CXBK mice.
The effect of morphine on the capsaicin-induced cough reflex was studied in mu 1-opioid receptor-deficient CXBK mice. There was no significant difference between the morphine-induced antitussive effect in CXBK mice and C57BL/6 mice, a progenitor strain. Furthermore, the antitussive effects of morphine in both the CXBK and C57BL/6 mice were antagonized by pretreatment with either naloxone or beta-funaltrexamine, a mu-opioid receptor antagonist, whereas pretreatment with naltrexonazine, a selective mu 1-opioid receptor antagonist, had no effect. Moreover, naltrindole, a selective delta-receptor antagonist, also had no significant effect on the antitussive effects of morphine in either CXBK or C57BL/6 mice. These results support our previous hypothesis that mu 2- rather than mu 1-opioid receptors are involved in morphine-induced antitussive effects.
Kamei
J
J
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Hoshi University, Tokyo, Japan.
Iwamoto
Y
Y
Suzuki
T
T
Misawa
M
M
Nagase
H
H
Kasuya
Y
Y
D000818:Animals; D000996:Antitussive Agents / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000494:pharmacology*; D017450:Receptors, Opioid, mu / Q000032:analysis / Q000187:drug effects / Q000502:physiology*
D000996:Antitussive Agents; D017450:Receptors, Opioid, mu; D009020:Morphine