Orexin-A up-regulates dopamine D2 receptor and mRNA in the nucleus accumbens Shell

Orexins-A (OrxA) and -B (OrxB) neuropeptides are synthesized by a group of neurons located in the lateral hypothalamus and adjacent perifornical area, which send their projections to the mesolimbic dopaminergic (DAergic) system including ventral tegmental area and nucleus accumbens (NAc), where orexin receptors are expressed. NAc plays a central role in reward-seeking behavior and drug abuse. NAc-neurons express dopamine-1 (D1R) and dopamine-2 (D2R) receptors. Orexins bind to their two cognate G-protein-coupled receptors, orexin-receptor type-1 (Orx₁R) and type-2 (Orx₂R). Orexin receptor signaling is involved in behaviors such as motivation and addiction. Orexin-containing neurons modulate DAergic activity that is key in synaptic plasticity induced by addictive drugs. However, the effect of OrxA on expression and content of DAergic receptors in NAc is unknown. The purpose of this study was to investigate whether OrxA can alter gene expression and protein levels of D1R/D2R in NAc. Gene expression was evaluated by real-time PCR analysis and protein levels by western blot in rats. The results show that intracerebroventricular (i.c.v.) injection of OrxA increases both gene transcription and protein content of D2R but fails to modify D1R. This effect was also confirmed with OrxA infusion in NAc/Shell. Our results demonstrate for the first time that OrxA induces up-regulation of gene and protein of D2R in NAc. These findings support the hypothesis that OrxA modulates the DAergic transmission and this may serve to understand how orexin signaling enhances DA responses at baseline conditions and in response to psychostimulants.

[Analysis of polymorphism rs1051730 of CHRNA3 in patients with dual pathology in a Mexican population]

INTRODUCTION

Epidemiological studies have described a high comorbidity of substance use disorders with another psychiatric disorder, which has been called dual pathology. However, the aetiological mechanisms underlying this association are still not fully understood.

AIM

To carry out a preliminary study of the effect of polymorphism rs1051730 of the gene group CHRNA5-CHRNA3-CHRNB4 through a case-control study.

SUBJECTS AND METHODS

A total of 225 subjects were selected and divided into three groups: those diagnosed with bipolar disorder, those with nicotine dependence, and subjects without nicotine dependence or any other psychiatric disorder. Genotyping was performed by real-time polymerase chain reaction. Genetic association analysis was performed using chi-square tests and multivariate logistic regressions.

RESULTS

On comparing allelic frequencies with the control group, we found that polymorphism rs1051730 was associated with nicotine dependence (p = 0.03), but not with bipolar disorder (p = 0.94).

CONCLUSION

Variant rs1051730 was associated with nicotine dependence in the Mexican population and showed the same effect in dual pathology. However, further studies are recommended to obtain conclusive results.

Comparative Analysis of Gene Expression Profiles Involved in Calcium Signaling Pathways Using the NLVH Animal Model of Schizophrenia

In this study, we evaluated the expression profile changes of genes that intervene in the calcium signaling pathway, in young and adult Wistar rats, using the animal model of neonatal lesion in ventral hippocampus (NLVH) (a recognized animal model for schizophrenia) and compared to the group of control animals (Sham). Through microarray technology, gene expression profiles were obtained from the three brain areas (nucleus accumbens, prefrontal cortex, and hippocampus) of young male Wistar rats (45 days) and adults (90 days) whether or not subjected to NLVH. The calcium signaling pathway reported a greater number of differentially expressed genes with z-score two values, > 2 (over-expression) and < - 2 (under-expression), in the three evaluated areas. The comparative analyses of this approach were performed in juvenile and adult rats with ventral hippocampal lesion in neonate rats (NLVH). NLVH influenced change expressions in various genes involved in Ca²⁺ homeostasis, including Cacna1d, Atp2a2, Adcy2, Ppp3cb, and Ptk2b. The expression of Adcy2, Ppp3cb, and Ptk2b genes changed in both age groups; therefore, the study of gene expression profiles between juvenile and adult rats may help to understand the molecular mechanisms of schizophrenia.

The role of C957T, TaqI and Ser311Cys polymorphisms of the DRD2 gene in schizophrenia: systematic review and meta-analysis

Background

The association between the dopamine D2 receptor (DRD2) gene and schizophrenia has been studied though no conclusive outcomes have been attained. The aim of this study was to perform a systematic review and meta-analysis to explore the relation between three polymorphisms of the DRD2 gene (C957T, TaqI and Ser311Cys) and schizophrenia.

Methods

The search was made in PubMed and EBSCO databases (up to February 2016). The systematic review included 34 case–control association studies (34 for C957T, 16 for TaqI and 36 for Ser311Cys). The association analysis comprised the allelic, additive, dominant, and recessive genetic models. The meta-analysis was performed following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement.

Results

The meta-analysis showed that TaqI (additive model: OR 0.57, 95% CI 0.30–1.14) and C957T (additive model: OR 0.75, 95% OR 0.58–0.97, recessive model: OR 0.79, 95% CI 0.64–0.98) exert a protective effect against developing schizophrenia. However, the sub-analysis for the C957T variant showed that this polymorphism exhibits a risk factor effect on Chinese individuals (allelic model: OR 1.33, 95% CI 1.04–1.70).

Conclusion

Our meta-analysis suggests an association of the DRD2 gene and the risk for schizophrenia, given that TaqI and C957T polymorphisms presented a protective effect against schizophrenia, and in the sub-analyses the C957T variant increased the risk for this disorder in the Chinese population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12993-016-0114-z) contains supplementary material, which is available to authorized users.

Response to the Fernández-Niño Comments on Hernández-Alvarado et al. Increase in Suicide Rates by Hanging in the Population of Tabasco, México between 2003 and 2012. Int. J. Environ. Res. Public Health 2016, 13, 552

We thank the comments of Fernández-Niño [1] addressing our article [2] "Increase in Suicide Rates by Hanging in the Population of Tabasco, Mexico between 2003 and 2012", which pointed out that the use of the epidemiological concept "prevalence" is not correctly applied in the present manuscript.

Increase in Suicide Rates by Hanging in the Population of Tabasco, Mexico between 2003 and 2012

BACKGROUND

Worldwide, the suicide rate is decreasing. To examine changes in the rates of completed suicide in the Mexican population from 2003 to 2012, we analyzed these changes according to: (i) the method of suicide; (ii) age group and (iii) gender.

METHODS

The data analyzed were obtained from governmental organizations from the State of Tabasco, Mexico. The data provided 1836 cases of subjects born and residing in Tabasco, who completed suicide in this state.

RESULTS

Suicide by hanging was a common choice of suicide method for Mexicans. The rate of suicide by hanging increased from 5.80 to 6.49 per 100,000 persons between 2003 and 2012, a rate percentage increase of 11.89%.

CONCLUSIONS

Hanging was found to be the most common choice of suicide in the Mexican population, probably because the materials required are easily available and the method does not require complicated techniques, especially in the 55-64 age group. Strategies for prevention and intervention should be developed for the Mexican population considering suicide rates by age group and gender.

[Association between the feeding behavior factors and the expression of DRD2 gene: a study of mexican monozygotic twins]

INTRODUCTION

The feeding behavior in humans is complex, with psychological, social, and cultural factors. This pathology consists of the desire to eat (reinforcement/reward) and the control of the act of eating (inhibitory control). It is well known that blocking post-synaptic D2 receptors in the nucleus accumbens induces a decrease of craving behavior. Due to this, to test hypothesis we measured the expression of the DRD2 gene and the expression of the type of feeding factor in a group of Mexican twins.

METHODS

In the study were included 18 pairs of twins (n = 36), reared together (at least up to 18 years old); native to Mexico City; to whom we applied the three factors of food instrument.

RESULTS

We observed a significant correlation between the "uncontrolled" factor and expression of the DRD2 gene (p < 0.03).

CONCLUSION

Therefore, we propose that the expression of the DRD2 gene in subjects is a linkage to the type of feeding factor.