Differential effects of μ-, δ- and κ-opioid receptor agonists on the discriminative stimulus properties of cocaine in rats

摘要: Abstract The effects of selective μ-, δ- and κ-opioid receptor agonists on the discriminative stimulus properties cocaine were examined in rats trained to discriminate between (10 mg/kg) saline. Cocaine produced a dose-related increase cocaine-appropriate responses all rats. In generalization tests, neither morphine (μ-opioid agonist) nor N -methyl- -7-(1-pyrrolidinyl)-1-oxaspiro[4,5]dec-8-11-4-benzofuranacetamide (U50,488H: generalized cocaine. On other hand, newly synthesized non-peptide δ-opioid agonist 2-methyl-4 α-(3-hydroxyphenyl)-1,2,3,4,4 ,5,12,12 α-octahydro-quinolino(2,3,3,– g )isoquinoline (TAN-67) partially (56.7% responses) Intracerebroventricular (i.c.v.) administration [ d -Ala 2 ]deltorphin II (peptide δ -opioid completely generalized, while ,MePhe 4 ,Gly-ol 5 ]enkephalin (DAMGO; μ-opioid -Pen , (DPDPE; 1 These results suggest that may be mediated by (especially -opioid) receptors. combination pretreatment with (3.0 TAN-67 10 significantly potentiated contrast, U50,488H (2.0 4.0 scarcely shifted Furthermore, potentiating effect 3.0 mg/kg was attenuated 2.0 U50,488H. not reversed either or modulate through different mechanisms, perhaps dopaminergic system. © 1997 Elsevier Science B.V.