title: C57BL/6J mice exhibit reduced dopamine D3 receptor-mediated locomotor-inhibitory function relative to DBA/2J mice.
abstract: Previous reports have identified greater sensitivity to the locomotor-stimulating, sensitizing, and reinforcing effects of amphetamine in inbred C57BL/6J mice relative to inbred DBA/2J mice. The dopamine D3 receptor (D3R) plays an inhibitory role in the regulation of rodent locomotor activity, and exerts inhibitory opposition to D1 receptor (D1R)-mediated signaling. Based on these observations, we investigated D3R expression and D3R-mediated locomotor-inhibitory function, as well as D1R binding and D1R-mediated locomotor-stimulating function, in C57BL/6J and DBA/2J mice. C57BL/6J mice exhibited lower D3R binding density (-32%) in the ventral striatum (nucleus accumbens/islands of Calleja), lower D3R mRNA expression (-26%) in the substantia nigra/ventral tegmentum, and greater D3R mRNA expression (+40%) in the hippocampus, relative to DBA/2J mice. There were no strain differences in DR3 mRNA expression in the ventral striatum or prefrontal cortex, nor were there differences in D1R binding in the ventral striatum. Behaviorally, C57BL/6J mice were less sensitive to the locomotor-inhibitory effect of the D3R agonist PD128907 (10 microg/kg), and more sensitive to the locomotor-stimulating effects of novelty, amphetamine (1 mg/kg), and the D1R-like agonist +/- -1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8,-diol hydrochloride (SKF38393) (5-20 mg/kg) than DBA/2J mice. While the selective D3R antagonist N-(4-[4-{2,3-dichlorphenyl}-1 piperazinyl]butyl)-2-fluorenylcarboxamide (NGB 2904) (0.01-1.0 mg/kg) augmented novelty-, amphetamine-, and SKF38393-induced locomotor activity in DBA/2J mice, it reduced novelty-induced locomotor activity in C57BL/6J mice. Collectively, these results demonstrate that C57BL/6J mice exhibit less D3R-mediated inhibitory function relative to DBA/2J mice, and suggest that reduced D3R-mediated inhibitory function may contribute to heightened sensitivity to the locomotor-stimulating effects of amphetamine in the C57BL/6J mouse strain. Furthermore, these data demonstrate that comparisons between C57BL/6J and DBA/2J mouse strains provide a model for elucidating the molecular determinants of genetic influence on D3R function.
authors.affiliation: Department of Psychiatry, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0559, USA. robert.mcnamara@psychiartry.uc.edu
authors.forename: R K
authors.initials: RK
authors.lastname: McNamara
authors.forename: B
authors.initials: B
authors.lastname: Levant
authors.forename: B
authors.initials: B
authors.lastname: Taylor
authors.forename: R
authors.initials: R
authors.lastname: Ahlbrand
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: J R
authors.initials: JR
authors.lastname: Sullivan
authors.forename: K
authors.initials: K
authors.lastname: Stanford
authors.forename: N M
authors.initials: NM
authors.lastname: Richtand
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001552:Benzazepines / Q000494:pharmacology; D001578:Benzopyrans / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005106:Exploratory Behavior / Q000502:physiology; D005449:Fluorenes / Q000494:pharmacology; D015870:Gene Expression / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology*; D010078:Oxazines / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D050637:Receptors, Dopamine D3 / Q000037:antagonists & inhibitors / Q000502:physiology*; D013045:Species Specificity; D014316:Tritium / Q000493:pharmacokinetics
chemical_list: D001552:Benzazepines; D001578:Benzopyrans; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D005449:Fluorenes; C116818:NGB 2904; D010078:Oxazines; D010879:Piperazines; D012333:RNA, Messenger; D050637:Receptors, Dopamine D3; D014316:Tritium; C062458:3,4,4a,10b-tetrahydro-4-propyl-2H,5H-(1)benzopyrano(4,3-b)-1,4-oxazin-9-ol; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine