Involvement of delta 2 opioid receptors in acute dependence on morphine in mice.
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 mumol/kg, s.c., 30 min before MS-100) and 5'-NTII (10 mumol/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 mumol/kg s.c.) did not precipitate jumping 4 hr after MS-100, small doses of NTB (1 and 2 mumol/kg, s.c.) administered 30 min before the challenge doses of naloxone increased substantially the ED50 value of naloxone. These results suggest that delta 2 opioid receptors are involved in acute dependence on morphine in mice.
Miyamoto
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Y
Department of Pharmacology, Medical School, University of Minnesota, Minneapolis.
Portoghese
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PS
Takemori
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AE
D000818:Animals; D004347:Drug Interactions; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology; D017879:Isothiocyanates; D008297:Male; D051379:Mice; D009020:Morphine; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D017465:Receptors, Opioid, delta / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019966:Substance-Related Disorders; D013861:Thiocyanates / Q000494:pharmacology
D017879:Isothiocyanates; D017465:Receptors, Opioid, delta; D013861:Thiocyanates; C068868:naltrindole benzofuran; C064283:naltrindole 5'-isothiocyanate; D004743:Enkephalin, Leucine; D009271:Naltrexone; C034318:enkephalin, Ser(2), Leu(5), Thr(6)-; D009020:Morphine