Neuroscience
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High voltage-activated (HVA) Ca2+ (CaV) channels are oligomeric complexes formed by an ion-conducting main subunit (Cavα1) and at least two auxiliary subunits (Cavβ and CaVα2δ). It has been reported that the expression of CaVα2δ1 increases in the dorsal root ganglia (DRGs) of animals with mechanical allodynia, and that the transcription factor Sp1 regulates the expression of the auxiliary subunit. Hence, the main aim of this work was to investigate the role of Sp1 as a molecular determinant of the exacerbated expression of CaVα2δ-1 in the nerve ligation-induced model of mechanical allodynia. ⋯ Interestingly, intrathecal administration of the Sp1 inhibitor mithramycin A (Mth) prevented allodynia and decreased the expression of Sp1 and CaVα2δ-1. Likewise, electrophysiological recordings showed that incubation with Mth decreased Ca2+ current density in the DRG neurons, acting mostly on HVA channels. These results suggest that L5/L6 SNL produces mechanical allodynia and increases the expression of the transcription factor Sp1 and the subunit CaVα2δ-1 in the DRGs, while Mth decreases mechanical allodynia and Ca2+ currents through HVA channels in sensory neurons by reducing the functional expression of the CaVα2δ-1 subunit.
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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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Reward-paired optogenetic manipulation of dopamine neurons can increase or decrease behavioral responding to antecedent cues when subjects have the opportunity for new learning, in accordance with a dopamine-mediated error learning signal. Here we examined the impact of reward-paired dopamine neuron inhibition on behavioral responding to reward-predictive cues after subjects had learned. We trained male TH-IRES-Cre mice to lever press for food reward in a progressive ratio procedure, a 2-cue choice procedure, or when continuously reinforced; in all procedures, completion of the response requirement was signaled by an auditory cue presented prior to food delivery. ⋯ Extinction-like behavioral responding was selective for learned associations: it was observed in the 2-cue choice procedure in which each subject was trained on two associations and inhibition was paired with reward for only one of the associations. Thus, inhibition during reward receipt can decrease responding to reward-predictive cues, sharing some features of behavioral extinction. These findings suggest changes in mesolimbic dopaminergic transmission at the time of experienced reward impacts subsequent responding to cues in well-trained subjects as predicted for a learning signal.