title: D1 receptors mediate dopamine action in the fetal suprachiasmatic nuclei: studies of mice with targeted deletion of the D1 dopamine receptor gene.
abstract: Studies in rodents suggest the presence of a dopaminergic system that influences the function of a biological clock in the hypothalamic suprachiasmatic nuclei (SCN). To provide insights into mechanisms of dopamine action in the SCN, we studied transgenic mice that had either one allele (+¿-) or both alleles (-/-) of the D1 dopamine receptor gene deleted, along with normal (+/+) littermates. As expected, receptor labelling autoradiography studies using [125I]SCH 23982 showed a complete absence of D1 dopamine receptor binding sites in the SCN of -/- animals. When pregnant mice from +¿- x +¿- matings were injected with the D1 receptor agonist SKF 38393, or the dopamine reuptake blocker GBR 12909 at day 19 of gestation, c-fos mRNA expression was observed in the SCN of +/+ fetuses. In contrast, c-fos mRNA induction was not seen in -/- or +¿- litter mates. Injection of cocaine into pregnant dams also resulted in robust SCN c-fos mRNA expression in +/+ mice. Increases in SCN c-fos mRNA expression were also seen in +¿- and -/- mice suggesting that cocaine action in the SCN involves both D1 receptor-dependent and -independent mechanisms. Collectively, our studies of transgenic mice deficient in D1 receptors support the presence of a functional dopaminergic system in the fetal SCN. We also identify D1 receptors as the prominent transducer of dopamine action in the fetal SCN.
authors.affiliation: Wells Center for Pediatric Research, Indiana University Medical School, Indianapolis, USA.
authors.forename: M
authors.initials: M
authors.lastname: Bender
authors.forename: J
authors.initials: J
authors.lastname: Drago
authors.forename: S A
authors.initials: SA
authors.lastname: Rivkees
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D001552:Benzazepines / Q000031:analogs & derivatives / Q000378:metabolism; D003042:Cocaine / Q000494:pharmacology; D003433:Crosses, Genetic; D004298:Dopamine / Q000502:physiology*; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000378:metabolism; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D005260:Female; D005333:Fetus; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010879:Piperazines / Q000494:pharmacology; D011247:Pregnancy; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D017447:Receptors, Dopamine D1 / Q000172:deficiency / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D013493:Suprachiasmatic Nucleus / Q000196:embryology / Q000502:physiology*; D014158:Transcription, Genetic / Q000187:drug effects; D014316:Tritium
chemical_list: C049558:8-iodo-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepine-7-ol; D001552:Benzazepines; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D018765:Dopamine Uptake Inhibitors; D010879:Piperazines; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D017447:Receptors, Dopamine D1; D014316:Tritium; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; C043425:vanoxerine; D003042:Cocaine; D004298:Dopamine