Neuroscience
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Two issues were examined regarding the trigeminal system in larval lampreys: (1) for normal animals, double labeling was used to confirm that the trigeminal system has a topological organization; (2) following trigeminal nerve root transections, double labeling was used to test whether the topological organization of the trigeminal system is restored. First, for normal animals, Alexa 488 dextran amine applied to the medial oral hood (anterior head) labeled trigeminal motoneurons (MNs) in the ventromedial part of the trigeminal motor nuclei (nVm) and axons of trigeminal sensory neurons (SNs) in the ventromedial part of the trigeminal descending tracts (dV). Also, Texas red dextran amine (TRDA) applied to the lateral oral hood labeled trigeminal MNs in the dorsolateral nVm and sensory axons in the dorsolateral dV. ⋯ In addition, double labeling indicated a restoration and refinement of the topological organization of the trigeminal system with increasing recovery times, but mainly for nVm. Despite the paucity of growth of trigeminal sensory axons in dV even at long recovery times (12-16 wks), a substantial percentage of experimental animals recovered trigeminal-evoked swimming responses and trigeminal-evoked synaptic responses in reticulospinal (RS) neurons. Following trigeminal nerve root injury, several mechanisms, including axonal guidance cues, probably contribute to the substantial restoration of the topological organization of the lamprey trigeminal system.
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Subjective well-being (SWB) is the eternal pursuit of all mankind. Individual differences in SWB may reflect the way of emotional processing. Neuroimaging studies have partly examined the neural mechanism of the individual differences in SWB using resting-state functional magnetic resonance imaging (rs-fMRI). ⋯ Results showed that SWB is positively correlated with the activation of right posterior cingulate cortex, left interior temporal gyrus and left angular gyrus for the comparison of negative stimulus and neutral stimulus, revealing that happy individuals may be more proactive to use attention transfer and behavioral inhibition strategies to decrease negative experiences during negative emotional processing. In addition, high SWB is associated with strong functional connectivity between high-level cognitive networks (e.g., frontal-parietal network) and low-level perceptual networks (e.g., sensorimotor network), and weak functional connectivity within default mode network and within low-level perceptual networks, indicating that the self-reflection, emotional regulation and cognitive control during negative facial emotion processing underlies the individual differences in SWB. These findings provide a novel insight to characterize the brain functional basis of the individual differences in SWB.
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Astrocytes comprise a heterogenic group of glial cells, which perform homeostatic functions in the central nervous system. These cells react to all kind of insults by changing the morphology and function that result in a transition from the quiescent to a reactive phenotype. Trimethyltin (TMT) intoxication, which reproduces pathological events in the hippocampus similar to those associated with seizures and cognitive decline, has been proven as a useful model for studying responses of the glial cells to neurodegeneration. ⋯ In CA1 subregion, GFAP+ astrocytes preserved their domain organization and responded with typical hypertrophy, while the hilar GFAP+ astrocytes developed atrophy-like phenotype and increased expression of vimentin and nestin 7 days after the exposure. Both reactive and atrophied-like astrocytes expressed Kir4.1 in CA1/CA3 and the hilus of DG, respectively, indicating that these cells did not change their potential for normal activity at this time point of pathology. Together, the results demonstrate the persistence of two protoplasmic morphotypes of astrocytes, with distinct appearance, function, and fate after TMT-induced neurodegeneration, suggesting their pleiotropic roles in the hippocampal response to neurodegeneration.
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Given the fact that both melatonin and nicotinamide mononucleotide (NMN) act as pleiotropic agents in various age-related cognitive disorders, we aimed to investigate the effect of these compounds separately and together on the cognitive outcomes, mitochondrial function, and apoptosis in aged rats. Forty old and ten young (24 and 3 months old, respectively) male Wistar rats were randomly allocated into five groups: Young+Normal saline (NS), Aged+NS, Aged+Melatonin, Aged+NMN, and Aged+melatonin+NMN. Melatonin (10 mg/kg) and NMN (100 mg/kg) were administered, separately or in combination for 28 every other day in aged animals. ⋯ Behavioral results revealed that NMN and melatonin separately or in combination, alleviate aging-induced memory impairment. Moreover, agents' co-administration declined mitochondrial dysfunction and apoptotic cell count both in PFC and HIP regions. The agents separately or in combination (more potent) could induce neuroprotective effect and improve learning and memory in aged animals.
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Sensitivity and reliability of animal behavioral assessment methods are critical for successful translation of in vitro findings to in vivo. Here we report a data transformation process in the elevated open platform task that generates a novel parameter, namely peak tolerance of fear (PTF) or its inversely correlated equivalent of anxiety quotient (AQ), to measure anxiogenic tendency in rodent. As compared to traditional parameters such as travel distance, time, or entries, PTF or AQ displays largely reduced data dispersion not only ingroup but also cross-study and cross-cohort, therefore representing a significant improvement of the methodology for rodent anxiety assessment.