title: Dopamine receptor antagonists prevent expression, but not development, of morphine sensitization.
abstract: The present experiments determined the effects of selective dopamine receptor antagonists on the initiation and expression of sensitization to the locomotor-stimulating effects of morphine in rats. Although both the dopamine D1 receptor antagonist R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzaz epine hydrochloride (SCH 23390, 0.25 mg/kg) and the dopamine D2 receptor antagonist eticlopride (0.1 mg/kg) suppressed the ability of morphine (10 mg/kg) to elicit sensitized locomotor activity during the course of a 12 day treatment schedule, subsequent tests with morphine alone revealed significant sensitization. Sensitization in the SCH 23390 + morphine group could not be attributed to dopamine D1 receptor supersensitivity caused by repeated SCH 23390 administration because electrophysiological recordings indicated that nucleus accumbens neurons in SCH 23390-treated rats were not more sensitive to the inhibitory effects of either dopamine or a dopamine D1 receptor-selective agonist. Thus, dopamine receptor stimulation may be involved in expression, but not development, of morphine sensitization.
authors.affiliation: Department of Neuroscience, Finch University of Health Sciences, Chicago Medical School, IL 60064-3095, USA.
authors.forename: M
authors.initials: M
authors.lastname: Jeziorski
authors.forename: F J
authors.initials: FJ
authors.lastname: White
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology*; D065127:Dopamine D2 Receptor Antagonists; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors*; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D012457:Salicylamides / Q000494:pharmacology
chemical_list: D001552:Benzazepines; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D017447:Receptors, Dopamine D1; D016194:Receptors, N-Methyl-D-Aspartate; D012457:Salicylamides; D009020:Morphine; C045989:eticlopride