title: The effects of dopamine D1 and D2 receptor antagonists on the rewarding effects of delta 1 and delta 2 opioid receptor agonists in mice.
abstract: The effects of the dopamine D1 antagonist SCH23390 and the D2 antagonist sulpiride on the rewarding effects of delta opioid receptor agonists were examined in mice. Both [D-Pen2, Pen5]enkephalin (DPDPE, 1-15 nmol, ICV), a selective delta 1 opioid receptor agonist, and [D-Ala2]deltorphin II (DELT, 0.5-5 nmol, ICV), a selective delta 2 opioid receptor agonist, produced a dose-dependent place preference in mice. The DPDPE (15 nmol, ICV)-induced place preference was abolished by BNTX (0.5 mg/kg, SC), a delta 1 opioid receptor antagonist, but not by NTB (0.5 mg/kg, SC), a delta 2 opioid receptor antagonist. In contrast, the DELT (5 nmol, ICV)-induced place preference was antagonized by NTB, but not BNTX. Pretreatment with SCH23390 (3 micrograms/kg, SC) abolished the DPDPE-induced place preference, but not affect the DELT-induced place preference. Moreover, pretreatment with sulpiride (40 mg/kg, SC) did not modify the place preference induced by DPDPE or DELT. In the present study, we found that the activation of both central delta 1 and delta 2 opioid receptors produced rewarding effects. Furthermore, these results suggest that the rewarding effects of delta 1 opioid receptor agonist may be produced through activation of the central dopaminergic system, especially dopamine D1 receptors, whereas the rewarding effects of delta 2 opioid receptor agonists may be produced by some other mechanism(s).
authors: Department of Pharmacology, School of Pharmacy, Hoshi University, Tokyo, Japan.
authors: T
authors: T
authors: Suzuki
authors: M
authors: M
authors: Tsuji
authors: T
authors: T
authors: Mori
authors: M
authors: M
authors: Misawa
authors: H
authors: H
authors: Nagase
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001552:Benzazepines / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology*; D065127:Dopamine D2 Receptor Antagonists; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology; D008297:Male; D051379:Mice; D009842:Oligopeptides / Q000494:pharmacology; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors*; D017465:Receptors, Opioid, delta / Q000819:agonists*; D012646:Self Administration; D013469:Sulpiride / Q000494:pharmacology
chemical_list: D001552:Benzazepines; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D004745:Enkephalins; D009842:Oligopeptides; D017447:Receptors, Dopamine D1; D017465:Receptors, Opioid, delta; C060209:deltorphin II, Ala(2)-; D013469:Sulpiride; D020881:Enkephalin, D-Penicillamine (2,5)-