Neuroscience
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Previous research has demonstrated antidepressant-like effects in rodents upon intracerebral inhibition of histone deacetylases (HDACs). Such effects have been reported for local HDAC inhibition in the nucleus accumbens, hippocampus, and amygdala. ⋯ Here we show that local infusion of the highly selective HDAC inhibitor, MS-275, into the medial prefrontal cortex exerts robust antidepressant-like effects in the chronic social defeat stress paradigm in mice. These findings provide further impetus for the assessment of HDAC inhibitors for the treatment of depression.
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While amyloid beta (Aβ) plays a central role in the development of Alzheimer's disease (AD), recent evidence suggests the involvement of arginine metabolism in AD pathogenesis. Earlier research has shown that a single intracerebroventricular (i.c.v.) infusion of pre-aggregated Aβ25-35 (the neurotoxic domain of the full-length Aβ) altered arginine metabolism in the rat hippocampus (particularly the CA2/3 and dentate gyrus (DG) sub-regions) and prefrontal cortex (PFC) at the time point of 8 days post-infusion. The present study measured the levels of L-arginine and its nine downstream metabolites (L-citrulline, L-ornithine, agmatine, putrescine, spermidine, spermine, glutamate, GABA and glutamine) in the hippocampus and PFC at the time points of 42 and 97 days following a single bilateral i.c.v. infusion of Aβ25-35 (30 nmol/rat) or Aβ35-25 (reverse peptide; 30 nmol/rat). ⋯ At the 97-day time point, however, there were decreased L-ornithine, GABA and putrescine levels, but increased glutamate/GABA ratio, in the PFC and increased spermine levels in the DG sub-region. Cluster analyses showed that L-arginine and its three main metabolites L-citrulline, L-ornithine and agmatine formed distinct groups, which changed as a function of Aβ25-35 at the 42-day and 97-day time points, particularly in the CA2/3 and PFC regions respectively. This study, for the first time, demonstrates that a single i.c.v. infusion of pre-aggregated Aβ25-35 leads to prolonged alterations in arginine metabolism in a region-specific and time-dependent manner, which further supports the involvement of arginine metabolism in AD pathogenesis.
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Several studies reveal that the beneficial effects of exercise interventions are dependent on the progression of Alzheimer's disease (AD). We have previously shown that long-term treadmill exercise begun before the onset of β-amyloid (Aβ) pathology prevents the deficits of cognition and long-term potentiation (LTP) in amyloid precursor protein (APP)/presenilin 1 (PS1) transgenic mice (8 months of age) paralleled by the reduction of soluble Aβ levels and Aβ deposition in the hippocampus. ⋯ In addition, exercise-induced enhancement of synaptic plasticity was accompanied by a significant reduction of soluble Aβ levels rather than Aβ plaque deposition. Therefore, the investigation demonstrates that long-term treadmill exercise has beneficial effects on cognition and synaptic plasticity even when the brain has developed Aβ deposition, and changes in soluble Aβ levels rather than Aβ plaque deposition may contribute to exercise-induced benefits.
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Individuals' reading skills are critical for their educational development, but variation in reading skills is known to be large. The present study used functional magnetic resonance imaging (fMRI) to examine the role of spontaneous brain activity at rest in individual differences in reading skills in a large sample of participants (N=263). Specifically, we correlated individuals' word-reading skill with their fractional amplitude of low-frequency fluctuation (fALFF) of the whole brain at rest and found that the fALFFs of both the bilateral precentral gyrus (PCG) and superior temporal plane (STP) were positively associated with reading skills. ⋯ A cross-validation confirmed that the individual differences in word-reading skills were reliably correlated with the fALFF values of the bilateral PCG and STP. A follow-up task-based fMRI experiment revealed that the reading-related regions overlapped with regions showing a higher response to sentences than to pseudo-sentences (strings of pseudo-words), suggesting the resting-state brain activity partly captures the characteristics of task-based brain activity. In short, our study provides one of the first pieces of evidence that links spontaneous brain activity to reading behavior and offers an easy-to-access neural marker for evaluating reading skill.
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Traumatic brain injury (TBI) is associated with a risk of neurodegenerative disease. Some suggest a link between TBI and motor neuron disease (MND), including amyotrophic lateral sclerosis (ALS). To investigate the potential mechanisms linking TBI to MND, we measured motor function and neuropathology following mild-TBI in wild-type and a transgenic model of ALS, G93A mutant mice. ⋯ Markers of inflammation (cell edema, astrogliosis and microgliosis) were detected at 24 and 72h in the brain and spinal cord in wild-type and G93A mice. Levels of F2-isoprostanes, a marker of oxidative stress, were increased in the spinal cord 24h post mild-TBI in wild-type mice but were not affected by TBI in G93A mice. In summary, our data demonstrate that mild-TBI induces inflammation and oxidative stress and negatively impacts muscle denervation and motor performance, suggesting mild-TBI can potentiate motor neuron pathology and influence the development of MND in mice.