A mode of action of morphine on a quickly learned conditioned suppression in mice.
Mice exhibited marked suppression of motor activity when placed in the same environment where they had previously received electric shocks. Morphine-HCl (20 mg/kg) markedly attenuated such a conditioned suppression in mice. The morphine-induced reduction of the conditioned suppression was antagonized by pretreatment with reserpine (0.1 and 0.5 mg/kg), haloperiodol, pimozide and alpha-methyl-p-tyrosine, but not atropine-sulfate, p-chlorophenylalanine, phenoxybenzamine-HCl or propranolol. Thus, it is possible that the potentiation of the dopaminergic neurotransmission in the brain is involved in the morphine-induced reduction of the conditioned suppression in mice.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001679:Biogenic Amines / Q000502:physiology; D003216:Conditioning, Operant / Q000187:drug effects*; D004347:Drug Interactions; D004558:Electric Stimulation; D010134:Fenclonine / Q000494:pharmacology; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D008781:Methyltyrosines / Q000494:pharmacology; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D010643:Phenoxybenzamine / Q000494:pharmacology; D010868:Pimozide / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D012110:Reserpine / Q000494:pharmacology; D019805:alpha-Methyltyrosine
D001679:Biogenic Amines; D008781:Methyltyrosines; D010643:Phenoxybenzamine; D010868:Pimozide; D019805:alpha-Methyltyrosine; D009020:Morphine; D001285:Atropine; D012110:Reserpine; D011433:Propranolol; D006220:Haloperidol; D010134:Fenclonine