Neuroscience
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Serotonin is a neurotransmitter that plays a role in regulating activities such as sleep, appetite, mood and substance abuse disorders; serotonin receptors 5-HT2AR and 5-HT2CR are active within pathways associated with substance abuse. It has been suggested that 5-HT2AR and 5-HT2CR may form a dimer that affects behavioral processes. Here we study the coevolution of residues in 5-HT2AR and 5-HT2CR to identify potential interactions between residues in both proteins. ⋯ We also discuss how co-expression of the receptors suggests the predicted interaction is functional. Finally, we analyze how several single nucleotide polymorphisms for the 5-HT2AR and 5-HT2CR genes affect their interaction. Our findings are the first to characterize the binding interface of 5-HT2AR/5-HT2CR and indicate a correlation between this interface and location of SNPs in both proteins.
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Calpain-mediated tau cleavage into the neurotoxic tau45-230 fragment plays an important role in Alzheimer's disease (AD). This tau fragment accumulates mainly in the cytoplasm of degenerating neurons. However, subcellular localization studies indicated that a pool of tau45-230 associates with the cytoskeleton in hippocampal neurons. ⋯ The data obtained also showed a significant reduction in actin filaments in tau45-230-expressing neurons. These changes in microtubules and actin filaments correlated with delayed neurite elongation and axonal differentiation in the presence of this tau fragment. Together, these results suggest that tau45-230 could exert its toxic effects, at least in part, by modifying the composition of the neuronal cytoskeleton and impairing neurite elongation in neurons undergoing degeneration.
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Mesolimbic dopamine has been implicated in reward learning. Fischbach-Weiss and Janak (this issue) use optogenetics to attenuate dopamine signaling and study its role in cue-driven motivated behavior.
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Recently, the empirical interest in religiousness and spirituality has grown, showing the association between the activity of a complex network of subcortical and fronto-parietal areas and explicit and implicit religious/spiritual representations. Importantly, while the causal link between parietal stimulation and implicit religiousness/spirituality has been demonstrated, the role of subcortical and medial cortical areas has not been directly investigated. Here, we assessed how implicit and explicit religious or spiritual representations are modulated by transcutaneous Vagus Nerve Stimulation (tVNS), a novel non-invasive method to stimulate subcortical and medial cortical structures. ⋯ Active-tVNS, compared to sham-tVNS, affected implicit spiritual, but not religious or control self-representations, reducing the strength of the automatic association between the self and the spiritual dimension. Explicit self-representations were left unchanged. Findings shed new light on the neurobiological mechanisms of implicit spirituality.
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Ghrelin is an important orexigenic brain-gut hormone that regulates feeding, metabolism and glucose homeostasis in human and rodents at multiple levels. Ghrelin functions by binding to its receptor, the growth hormone secretagogue receptor 1a (GHS-R1a), which is widely expressed both inside and outside of the brain. Both acute and chronic calorie restrictions (CRs) were reported to increase endogenous ghrelin levels and lead to beneficial effects on brain functions, including anti-anxiety effects, anti-depressive effects, and memory improvement. ⋯ This effect was abolished by a GHS-R1a antagonist, suggesting a GHS-R1a dependent mechanism. Ad-libitum refeeding masked behavioral responses induced by acute CR in both Ghsr-/- and Ghsr+/+ mice. Altogether, our findings indicate that acute and chronic CRs mitigate anxiety- and despair-like behaviors with different physiological mechanisms, with the former being dependent on endogenous ghrelin release and GHS-R1a signaling, while the latter may not be.