Involvement of δ2 opioid receptors in acute dependence on morphine in mice

Y. Miyamoto, P. S. Portoghese, A. E. Takemori

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35 Scopus citations


The effects that naltriben (NTB) and naltrindole 5'-isothiocyanate (5'- NTII) have on acute morphine dependence were investigated in mice. The degree of acute dependence was estimated by the ED50 value of s.c.-administered naloxone that was required to precipitate withdrawal jumping 4 hr after s.c. injection of 100 mg/kg of morphine sulfate (MS-100). Pretreatments with NTB (10 μmol/kg, s.c., 30 min before MS-100) and 5'-NTII (10 μmol/kg, s.c., 24 hr before MS-100) increased the ED50 values of naloxone compared to those of the respective saline-treated control mice. Although NTB itself (up to 10 μmol/kg, s.c.) did not precipitate jumping 4 hr after MS-100, small doses of NTB (1 and 2 μmol/kg, s.c.) administered 30 min before the challenge doses of naloxone increased substantially the ED50 value of naloxone. These results suggest that δ2 opioid receptors are involved in acute dependence on morphine in mice.

Original languageEnglish (US)
Pages (from-to)1325-1327
Number of pages3
JournalJournal of Pharmacology and Experimental Therapeutics
Issue number3
StatePublished - 1993


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