Quinpirole Increases Melatonin-Augmented Pentobarbital Sleep via Cortical ERK, p38 MAPK, and PKC in Mice

Sleep, which is an essential part of human life, is modulated by neurotransmitter systems, including gamma-aminobutyric acid (GABA) and dopamine signaling. However, the mechanisms that initiate and maintain sleep remain obscure. In this study, we investigated the relationship between melatonin (MT) and dopamine D2-like receptor signaling in pentobarbital-induced sleep and the intracellular mechanisms of sleep maintenance in the cerebral cortex. In mice, pentobarbital-induced sleep was augmented by intraperitoneal administration of 30 mg/kg MT. To investigate the relationship between MT and D2-like receptors, we administered quinpirole, a D2-like receptor agonist, to MT- and pentobarbital-treated mice. Quinpirole (1 mg/kg, i.p.) increased the duration of MT-augmented sleep in mice. In addition, locomotor activity analysis showed that neither MT nor quinpirole produced sedative effects when administered alone. In order to understand the mechanisms underlying quinpirole-augmented sleep, we measured protein levels of mitogen-activated protein kinases (MAPKs) and cortical protein kinases related to MT signaling. Treatment with quinpirole or MT activated extracellular-signal-regulated kinase 1 and 2 (ERK1/2), p38 MAPK, and protein kinase C (PKC) in the cerebral cortex, while protein kinase A (PKA) activation was not altered significantly. Taken together, our results show that quinpirole increases the duration of MT-augmented sleep through ERK1/2, p38 MAPK, and PKC signaling. These findings suggest that modulation of D2-like receptors might enhance the effect of MT on sleep.

Effects of sleep deprivation on the gene expression of 5-serotonin 1A receptor and dopamine 2 receptor in different brain regions of rats / 中华行为医学与脑科学杂志

Objective To analyze the influence of sleep deprivation on expression of serotonin receptor 1A(5-HT1A) and dopanine-2 receptor (D2R) gene and to explore the differences between different neurotransmitter pathways involved in sleep regulation through measuring the gene expression of 5-HT1A and D2R in regions of hippocampus,hypothalamus and striatum with different sleep deprivation models.Methods Sleep deprivation was performed to male SD rats of 10-week-old for 24 hours,48 hours and 72 hours respectively as the experimental group and a control group was taken for comparison.The expressions of 5-HT1A and D2R gene in regions of hippocampus,hypothalamus and striatum were detected through RT-PCR technique to analyze the influence of sleep deprivation on gene expression in different regions.Results Sleep deprivation had a significant effect on the gene expression of 5-HT1A in regions of hippocampus and striatum(F=56.203,P＜0.01 ; F=77.288,P＜0.01).The three experimental groups were all superior to the control group and the difference was of statistic significance(P＜0.05).In the hippocampus region,the expression quantity of the 72 hours group(0.618±0.054) was superior to that of the 24 hours group and of the 48 hours group(24 hours:0.404±0.023,P＜0.01 ;48 hours:0.455±0.042.P＜0.05).In the striatum region,the differences between the 24 hours group(0.413±0.033),the 48 hours group(0.464±0.034)and the 72 hours group(0.610±0.040) were all of statistic significance(all P＜0.05).Sleep deprivation had a significant effect on the expression of D2R gene in regions of hippocampus and striatum(F=74.708,P＜0.01 ; F=80.687,P＜0.01).The expression quantity of the three experimental groups in regions of hippocampus (24 hours:0.386±0.027,48 hours:0.318±0.014,72 hours:0.250±0.010) and striatum(24 hours:0.396±0.013,48 hours:0.349±0.017,72 hours:0.260±0.013) were all inferior to the control group.The differences were of statistic significance (all P＜0.05).There was a negative correlation between the gene expressions of 5-HT1A and D2R of rats of the three experience groups(all P＜0.05).Conclusion For the sleep deprivation rats,the gene expression of 5-HT1A rises while that of D2R falls in regions of hippocampus,hypothalamus,and there is a negative correlation between the expressions of the two genes.

Development of Dual Reporter System of Mutant Dopamine 2 Receptor (D2R) and Sodium Iodide Symporter (NIS) Transgenes / 대한핵의학회잡지

PURPOSE: Both human NIS and mutant D2R transgenes are proposed as reporting system in transplanted cell tracking. Using hepatoma cell lines, we constructed a dual reporter system containing human sodium-iodide symporter (hNIS) and dopamine 2 receptor (D2R) and compared its characteristics. MATERIALS AND METHODS: The recombinant plasmid (pIRES-hNIS/D2R) was constructed with IRES (internal ribosome entry site) under control of the CMV promoter. pIRES-hNIS/D2R was transfected to human hepatoma SK-Hep1 cell line with lipofectamine. HEP-ND (SK-Hep1-hNIS/D2R) cells stably expressing hNIS and D2R was established by selection with G418 for two weeks. RT-PCR was performed to investigate the expression of both hNIS and D2R genes. The expressions of hNIS and D2R were measured by 125I uptake assays and receptor binding assays. Specific binding of D2R to [3H]spiperone was verified by Scatchard plot with (+) butaclamol as a specific inhibitor. K (d) and B (max) values were estimated. The correlation between hNIS and D2R expression was compared by using each clone. RESULTS: Similar quantities of hNIS and D2R genes were expressed on HEP-ND as RT-PCR assays. HEP-ND cells showed 30 to 40 fold higher radioiodine uptakes than those of parental SK-Hep1 cells. 125I uptake in HEP-ND cells was completely inhibited by KClO4, a NIS inhibitor. Specific binding to HEP-ND cells was saturable and the K (d) and B (max) values for HEP-ND cells were 2.92 nM, 745.25 fmol/mg protein and 2.91nM, 1323 fmole/mg protein in two clones, respectively. The radioiodine uptake by hNIS activity and D2R binding was highly correlated. CONCLUSION: We developed a dual positron and gamma imaging reporter system of hNIS and D2R in a stably transfected cell line. We expect that D2R and hNIS genes can complement mutually as a nuclear reporting system or that D2R can be used as reporter gene when hNIS gene were used as a treatment gene.

Specificity of Dopamine-2 Receptor Agonist on Eyeball Growth in Chicken Model of Myopia

The authors examined the specificity of the dopamine-2 receptor for eyeball growth of the experimental myopic chicken eyes. Two day-old white Leghorn chickens were monocularly deprived of vision by lid suture of the right eyes. We measured the axial lengths of chicken's eyes by ultrasonography at the 2nd day and the 4th weeks. The right eyes of the first group were instillated with 0.04cc of tris buffer solution, those of the second and third group were instillated with 0.04cc of 0.02% SKF38393 hydrochloride solution and 0.02% bromocriptine solution individually. All solutions were instillated into the right eyes two times per day during 4 weeks. At the 2nd day of the age, the axial lengths of the first group's eyeballs were 7.83 +/- 0.14mm in the right, 7.87 +/- 0.15mm in the left eyes, 7.78 +/- 0.16mm in the right eyes, 7.77 +/- 0.11mm in the left eyes of the second group and 7.89 +/- 0.12mm in the right eyes, 7.87 +/- 0.12mm in the left eyes of the third group. Each group was not statistically different (p>0.05). But at the four weeks of the age, the axial lengths of the lid sutured right chicken eyeball were 11.39 +/- 0.27mm in the first group, 11.40 +/- 0.40mm in the second group and 11.20 +/- 0.40mm in the third group, The third group was statistically different from the first or 2nd group (p<0.05). The growth of the axial lengths of the right chicken eyeballs from the 2nd day to the 4th week of the age was 3.50 +/- 0.35mm in the first, 3.63 +/- 0.42mm in the second and 3.21 +/- 0.29mm in the third group. The right eyes of the third group were found significantly less growth than those of other groups. These results suggest that dopamine-2 receptor playa role in eyeball growth.