Anna G. Galyamina
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Researcher at FRC Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences
There are experimental data that mixed anxiety/depression-like state induced by chronic social defeat stress is accompanied by development of anxiety and downregulation of serotonergic gene expression in the midbrain raphe nuclei of male mice. The paper aimed to study the effect of chronic lithium chloride (LiCl) on anxious behaviors and the expression of serotonergic genes (Tph2, Slc6a4, Htr1a, Htr5b) in the midbrain raphe nuclei of defeated mice. Slight anxiolytic effects of LiCl were found on the commucativeness in the partition test, and anxiogenic-like effects, estimated by the elevated plus-maze and social interactions tests. Chronic LiCl treatment induced overexpression of the serotonergic genes in the midbrain raphe nuclei of defeated mice. We can assume that effects of LiCl, rather anxiogenic, may be due to activation of serotonergic system induced by hyperexpression of serotonergic genes. Our findings will allow to understand the factors involved in the positive and side effects of lithium on anxiety and function of serotonergic genes which are involved into mechanisms of depression.
There are many psychiatric medications targeting the activity of SLC transporters. Therefore, further research is needed to elucidate the expression profiles of the Slc* genes, which may serve as markers of altered brain metabolic processes and neurotransmitter activities in psychoneurological disorders. We studied differentially expressed Slc genes using the transcriptomic profiles in the ventral tegmental area (VTA), nucleus accumbens (NAcc), and prefrontal cortex (PFC) of male mice with psychosis-like behavior induced by repeated aggression experience in daily agonistic interactions which are accompanied by wins. Most of differentially expressed Slc genes in the VTA and NAcc (12 of 17 and 25 of 26, respectively) were downregulated, which was not the case in the PFC (6 and 5, up- and down, respectively). Also, the majority of these genes were shown to have brain region-specific expression profiles. In the VTA and NAcc altered expression was observed for the genes encoding the transporters of neurotransmitters as well as inorganic and organic ions, amino acids, metals, glucose, etc. This means alteration in transport functions for many substrates, which results in complete disruption of all cellular and neurotransmitter processes. The neurotransmitter systems, especially, the dopaminergic one, in male mice with positive fighting experience in daily agonistic interactions undergo changes leading to profound genomic modifications which include downregulated expression of the majority of the Slc* genes at least in the VTA and NAcc, which is attributable to chronic stimulation of the reward systems. ### Competing Interest Statement The authors have declared no competing interest.
BMC Neuroscience, 2020-03-26
A mouse model of chronic social conflicts was used to analyze dorsal striatum neurons implicated in cAMP-mediated phosphorylation activation pathways specific for Medium Spiny Neurons (MSNs). Based on expression correlation analysis, we succeeded in dissecting Drd1- and Drd2-dopaminoceptive neurons (D1 and D2, correspondingly) gene pathways. We also found that D1 neurons feature previously reported two states, passive and active ones, represented in our analysis by distinct, negatively correlated gene clusters. The correlation based gene pathways strongly corroborate the phosphorylation cascades highlighted in the previous studies, implying that the expression-based viewpoint corresponds to phosphorylation/ dephosphorylation interplay in each type of neurons. Notably, D2 neurons showed the largest Ppp1r1b (encoding DARPP-32) expression modulation impact, implying that Ppp1r1b expression dynamics is mostly associated with neuroendocrine response mediated by Penk/Pdyn genes expression in D2 neurons. We observed that under defeat stress in chronic social conflicts mice exhibited reduced motor activity as well as overall depression of dopamine-mediated MSNs activity, while aggressive mice exhibited motor hyperactivity and an increase in both D1-active phase and D2 MSNs genes expression. Based on alternative transcript isoforms expression analysis, it was assumed that many genes (Drd1, Adora1, Pde10, Ppp1r1b, Gnal), specifically those in D1 neurons, apparently remain transcriptionally repressed via the reversible mechanism of promoter CpG island silencing, resulting in alternative promoter usage following profound reduction in their expression rate.