Cocaine-like discriminative stimulus properties of the delta-selective opioid receptor agonist, [D-Pen2,L-Pen5]enkephalin, in the rat.
The delta-selective opioid receptor agonist, [D-Pen2,L-Pen5]enkephalin (DPLPE) (10 micrograms i.c.v.), fully generalized to cocaine cue in the rat trained to discriminate 10 mg/kg of cocaine from vehicle. The cocaine-like discriminative stimulus effects of DPLPE were almost completely reversed by naltrindole (56 micrograms i.c.v.), a delta-selective opioid receptor antagonist. In contrast, the mu-selective opioid receptor agonist [D-Ala2,NMePhe4,Gly-ol]enkephalin (DAMGO) (0.03-0.3 micrograms i.c.v.) failed to generalize to cocaine cue. These results suggest that the discriminative stimulus effects of cocaine are mediated through the activation of delta-opioid receptors.
Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Meijo University, Nagoya, Japan.
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Ukai
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Mori
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Kameyama
D000818:Animals; D003042:Cocaine / Q000494:pharmacology*; D004193:Discrimination Learning / Q000187:drug effects*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D005795:Generalization, Stimulus / Q000187:drug effects*; D007211:Indoles / Q000494:pharmacology; D009019:Morphinans / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives*; D051381:Rats; D017465:Receptors, Opioid, delta / Q000187:drug effects*; D017450:Receptors, Opioid, mu / Q000187:drug effects
D004745:Enkephalins; D007211:Indoles; D009019:Morphinans; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009271:Naltrexone; D020881:Enkephalin, D-Penicillamine (2,5)-; C055382:naltrindole; D003042:Cocaine