Serotoninergic mechanisms of the effects of neurotensin on passive avoidance behavior in rats

Effects of psychotropic agents on extinction of lever-press avoidance in a rat model of anxiety vulnerability

Avoidance and its perseveration represent key features of anxiety disorders. Both pharmacological and behavioral approaches (i.e., anxiolytics and extinction therapy) have been utilized to modulate avoidance behavior in patients. However, the outcome has not always been desirable. Part of the reason is attributed to the diverse neuropathology of anxiety disorders. Here, we investigated the effect of psychotropic drugs that target various monoamine systems on extinction of avoidance behavior using lever-press avoidance task. Here, we used the Wistar-Kyoto (WKY) rat, a unique rat model that exhibits facilitated avoidance and extinction resistance along with malfunction of the dopamine (DA) system. Sprague Dawley (SD) and WKY rats were trained to acquire lever-press avoidance. WKY rats acquired avoidance faster and to a higher level compared to SD rats. During pharmacological treatment, bupropion and desipramine (DES) significantly reduced avoidance response selectively in WKY rats. However, after the discontinuation of drug treatment, only those WKY rats that were previously treated with DES exhibited lower avoidance response compared to the control group. In contrast, none of the psychotropic drugs facilitated avoidance extinction in SD rats. Instead, DES impaired avoidance extinction and increased non-reinforced response in SD rats. Interestingly, paroxetine, a widely used antidepressant and anxiolytic, exhibited the weakest effect in WKY rats and no effects at all in SD rats. Thus, our data suggest that malfunctions in brain catecholamine system could be one of the underlying etiologies of anxiety-like behavior, particularly avoidance perseveration. Furthermore, pharmacological manipulation targeting DA and norepinephrine may be more effective to facilitate extinction learning in this strain. The data from the present study may shed light on new pharmacological approaches to treat patients with anxiety disorders who are not responding to serotonin re-uptake inhibitors.

Association of Neurotensin receptor 1 gene polymorphisms with processing speed in healthy Chinese-Han subjects

Neurotensin modulates dopamine and serotonin transmission in the brain. The study investigated whether genetic polymorphisms in the Neurotensin receptor 1 gene were associated with performance on processing speed and executive function. A total of 129 healthy Chinese-Han volunteers were recruited. Genotyping for three SNPs, including rs6090453, rs6011914, and rs2427422, was analyzed by using a PCR and a restriction fragment length polymorphism analysis. Performances of processing speed and executive function were assessed by using Trail Making Test-A (TMT-A), Wisconsin Card Sorting Test, and Stroop Color-Word Test. We found significant differences in the outcomes of TMT-A score among rs6090453C/G (F(2,126)=4.405, P=0.014) and rs2427422A/G (F(2,126)=7.498, P=0.001) genotypes. Neurotensin receptor 1 SNP polymorphisms were significantly associated with the variance in processing speed performance in a sample of Chinese college students.

A novel approach of homozygous haplotype sharing identifies candidate genes in autism spectrum disorder

Autism spectrum disorder (ASD) is a highly heritable disorder of complex and heterogeneous aetiology. It is primarily characterized by altered cognitive ability including impaired language and communication skills and fundamental deficits in social reciprocity. Despite some notable successes in neuropsychiatric genetics, overall, the high heritability of ASD (~90%) remains poorly explained by common genetic risk variants. However, recent studies suggest that rare genomic variation, in particular copy number variation, may account for a significant proportion of the genetic basis of ASD. We present a large scale analysis to identify candidate genes which may contain low-frequency recessive variation contributing to ASD while taking into account the potential contribution of population differences to the genetic heterogeneity of ASD. Our strategy, homozygous haplotype (HH) mapping, aims to detect homozygous segments of identical haplotype structure that are shared at a higher frequency amongst ASD patients compared to parental controls. The analysis was performed on 1,402 Autism Genome Project trios genotyped for 1 million single nucleotide polymorphisms (SNPs). We identified 25 known and 1,218 novel ASD candidate genes in the discovery analysis including CADM2, ABHD14A, CHRFAM7A, GRIK2, GRM3, EPHA3, FGF10, KCND2, PDZK1, IMMP2L and FOXP2. Furthermore, 10 of the previously reported ASD genes and 300 of the novel candidates identified in the discovery analysis were replicated in an independent sample of 1,182 trios. Our results demonstrate that regions of HH are significantly enriched for previously reported ASD candidate genes and the observed association is independent of gene size (odds ratio 2.10). Our findings highlight the applicability of HH mapping in complex disorders such as ASD and offer an alternative approach to the analysis of genome-wide association data.