Neuroscience
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Itch induces a desire to scratch and leads to skin damage in some severe conditions. Much progress has been made in the peripheral and spinal level, and recent findings suggested that we need to focus on the central circuitry mechanism. However, the functional role of the thalamus in itch signal processing remains largely unknown. ⋯ We found that the calcium signal of Po neurons was increased during the histaminergic itch-induced scratching behavior in the cheek model, and pharmacogenetic suppression of Po neurons reduced the scratching behaviors. Retrograde mapping results suggested that the Po receives information from the somatosensory cortex, motor cortex, parabrachial nucleus (PBN), the principal sensory trigeminal nucleus (PrV) and the spinal trigeminal nucleus (SpV), which participate in itch signal transmission from head and body. Thus, our study indicates that the Po is critical in modulating facial histaminergic itch signal processing.
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Neurons in the lateral habenula (LHb) are activated by reward omission and inhibited by reward delivery-reward processing functions opposite those of midbrain dopaminergic neurons. To further explore this, we examined the role of the LHb in associating a conditioned stimulus (CS) with the absence of an unconditioned stimulus (US) in an appetitive Pavlovian-conditioning paradigm. Rats underwent training in which a CS (light) was either paired (100% CS-US contingency) or unpaired (0% CS-US contiguity and negative contingency) with an US (food). ⋯ The number of c-Fos-positive signals in LHb neurons projecting to dopaminergic midbrain neurons was higher in the unpaired group than in the paired group. Excitotoxic LHb lesions did not affect the acquisition of conditioned behaviors in the association of a CS with the presence or absence of an US. Significant increases in the numbers of c-Fos-positive neurons in the unpaired group suggest that LHb neurons engage in the process that associates a CS with the absence of an US.
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Serotonin is an important neurotransmitter of the brain, but its role in song control remains to be fully demonstrated. Using male zebra finches (Taeniopygia guttata) that have song learning and production capabilities, we analysed the serotonin expression levels in the song nuclei and adjacent areas (peri-song nuclei) using immunohistochemistry. Key song nuclei were identified using combinations of Hoechst, choline acetyltransferase, and a neurofilament (NN18) marker in reference to the ZEBrA atlas. ⋯ However, the mean serotonin expression (in order of highest first) in the peri-song nuclei regions was: peri-DM > peri-nXIIts > supra-peri-HVC > peri-RA > peri-DLM > peri-Area X > infra-peri-HVC > peri-VRG > peri-LMAN > peri-Nif. Interestingly, serotoninergic fibers immunostained for serotonin or the serotonin transporter can be found as a basket-like peri-neuronal structure surrounding cholinergic cell bodies, and appear to form contacts onto dopaminergic neurones. In summary, serotonin fibers are present at discrete song nuclei, and peri-song nuclei regions, which suggest serotonin may have a direct and/or modulatory role in song control.
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Impulsivity includes hasty actions, social intrusiveness or premature decision-making. Neuropeptides like oxytocin alleviate haste and anxiety, and affect fear conditioning. However, no investigations have been done via gene-network based approach with cognitive and interventional genetic association studies to scrutinize the link between impulsive behavior and oxytocin. ⋯ Oxytocin group and participants with GG genotype showed a significantly decreased commission error and increased inhibition. This means that oxytocin alleviated impulsive behavior, and subjects with GG genotype had lower rate of impulsivity than those with GA and AA genotypes. rs2254298 may modulate the function or expression of the OXTR gene, implying that G allele may increase the expression of OXTR gene compared to A allele. We suggest that intranasal oxytocin may notably moderate impulsive behavior and tendency to make hasty or premature decisions.
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The role of the anterior thalamic nuclei (ATN) has been proven in different learning and memory tasks. The ATN consist of three main subnuclei, the anterodorsal (AD), anteroventral (AV) and anteromedial (AM), which have different biological characteristics such as distinct circuitry, cell population and neurotransmitter content. The role of ATN subnuclei in learning and memory has been shown in several studies. ⋯ The AM inactivation had no effect on acquisition of both tasks while it impaired the PA consolidation and MWM retrieval. However, the AD inactivation could not disrupt memory phases in the PA task but impaired the MWM retrieval. In conclusion, it seems that the ATN distinct subnuclei differently affect different phases of memory in these two tasks.