Dysregulation of striatal dopamine D2/D3 receptor-mediated by hypocretin induces depressive behaviors in rats.

BACKGROUND: The dysregulation of the dopamine system contributes to depressive-like behaviors in rats, and the neurological functions regulated by hypocretin are severely affected in depression. However, whether suvorexant plays a role in alleviating depression by affecting the dopamine system is unclear. METHODS: To preliminarily explore the mechanism of suvorexant (10 mg/kg) in the treatment of depression, the mRNA and protein expression of TH, Drd2, Drd3, GluN2A, DAT, and GluN2B in the striatum of rats was quantified by qPCR and western blotting. The plasma hypocretin-1 and dopamine levels and the striatal dopamine levels were determined by ELISA. RESULTS: i) Compared to those of the control group, chronic unpredictable mild stress (CUMS) rats showed depressive-like behaviors, which were subsequently reversed by treatment with suvorexant. ii) The mRNA and protein expressions of TH, Drd2, Drd3, GluN2A, and GluN2B in the striatum of CUMS were significantly increased compared with those in the controls, but decreased after suvorexant treatment. iii) Compared with those in the control group, the plasma and striatal dopamine levels of CUMS decreased while plasma hypocretin-1 levels increased, which was reversed after suvorexant treatment. LIMITATIONS: i) The suvorexant is a dual hypocretin receptor antagonist; however, the responsible receptor is unclear. ii) We only focused on related factors in the striatum but did not explore other brain regions, nor did we directly explore the relationship among these factors. CONCLUSION: Depressive-like behaviors induced by CUMS can be reversed by suvorexant, and the therapeutic effects of suvorexant may be mediated by affecting the dopamine system.

Magnetic properties of street dust in Shanghai, China and its relationship to anthropogenic activities.

Magnetic properties of urban street dust can be used as a proxy of urban pollution. In this study, magnetic measurements on 160 street dust samples, collected from five different functional areas (industrial, traffic, commercial, residential and clean areas) in sixteen administrative districts in Shanghai, China, were systematically conducted. It is showed that magnetic carriers were predominately coarse-grain ferrimagnetic particles. Meantime, concentration-related magnetic parameters showed significant variations among the functional areas and administrative units. Magnetic susceptibility (χ) decreased in the following order: industrial area (IA) > traffic area (TA) > commercial area (CoA) > residential area (RA) > clean area (ClA). Moreover, combined with the analyses conducted using a scanning electron microscope and an energy dispersive X-ray spectrometer (SEM-EDX), it is found that spherical magnetic particles originating mainly from anthropogenic sources were abundant in industrial areas. Baoshan district, which is heavily impacted by industrial activities, showed the highest χ value among the administrative units. Additionally, the correlations of street dust χ value with population, value of industrial output and the gross domestic product (GDP) in Shanghai and other cities indicated that χ is positively correlated with the city GDP as well as the population size (PS) to some extent. This study demonstrates that magnetic parameters of street dust can be used as an effective tool for monitoring environmental pollution and industrial activities in urban environments.

Relationship between magnetic properties and heavy metal contamination of street dust samples from Shanghai, China.

In this study, for exploring the relationship between selected magnetic properties and heavy metal contamination of street dust in Shanghai, China, 160 samples from five different functional areas (industrial, high traffic density, commercial, residential and "clean" area) were collected and investigated by magnetic and geochemical analyses. It is found that the street dust exhibits a high concentration of ferrimagnetic minerals, which are predominantly coarse-grained. Meantime, the magnetic properties of the street dust samples exhibit significant differences between the five functional areas, namely, the values of χlf, SIRM, χARM, and S- 300 mT in the five functional areas all decrease in the following order: industrial > commercial > high traffic density > residential > clean. Calculation of enrichment factors (EF) and the Tomlinson pollution load index (PLI) indicates that the street dust samples are highly polluted in terms of their degree of heavy metal contamination. The values of χlf, SIRM, and χARM are significantly correlated with Pb, Cu, Zn, Ni, Mn, Cr, Ba, and Fe concentrations as well as PLI. In accordance with similar findings in other urban areas, these results indicate that magnetic parameters, such as χlf, SIRM, χARM, can be used as an efficient proxy for heavy metal pollution and anthropogenic activities in Shanghai. In addition, the results demonstrate that it is possible to distinguish different heavy metal pollution sources using a combination of magnetic measurements and geochemical analysis.