Neuroscience
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Inflammatory mechanisms were recently identified as contributors to delayed neuronal damage after ischemic stroke. However, therapeutic strategies are still lacking, probably related to the outstanding standardization on inflammatory cell recruitment emerging from predominantly artificial stroke models, and the uncertainty on functional properties of distinct subpopulations. Using a rodent model of stroke that closely reflects human embolic ischemia, this study was focused on the local recruitment of immunoreactive cells as well as their functional and regional characterization. ⋯ Ischemia caused an increase of lymphoid cells in close vicinity to the affected vasculature, while further analyses allowed separation into natural killer cells, natural killer T cells, T cells (added by an unconventional CD11b(+)/CD3(+) population) and two subpopulations of B cells. Taken together, our study provides novel data on the local inflammatory response to experimental thromboembolic stroke. As concomitantly present neutrophils, monocytes/macrophages and lymphoid cells in the early stage after ischemia induction correspond to changes seen in human stroke, future stroke research should preferably use animal models with relevance for clinical translation.
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Deposits of amyloid-β (Aβ) protein are one of the hallmarks of Alzheimer's disease (AD). Numerous studies report that the Aβ peptide, especially in the oligomeric form, causes memory decline and other cognitive deficits. However, there have been very few effective interventions for termination or even delay of AD progression. ⋯ In addition, we show that Aβ-induced loss of filopodia and spine density in cultured hippocampal neurons was prevented by administration of BBG. We conclude that BBG prevents the learning and memory impairment and cognitive deficits induced by the toxicity of soluble Aβ, and improves the development of dendritic spines in hippocampal neurons in an AD model mouse. Considering the safety and blood-brain-barrier (BBB)-permeability of BBG, our data suggest a potential for BBG as a new therapy for AD.
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Neurons in the superficial layers of the entorhinal cortex provide the hippocampus with the majority of its cortical sensory input, and also receive the major output projection from the parasubiculum. This puts the parasubiculum in a position to modulate the activity of entorhinal neurons that project to the hippocampus. These brain areas receive cholinergic projections that are active during periods of theta- and gamma-frequency electroencephalographic (EEG) activity. ⋯ Application of the K(+) channel antagonist Ba(2+) depolarized neurons and enhanced temporal summation, but did not block further facilitation of train-evoked responses by ZD7288. The Ih-dependent facilitation of synaptic responses can therefore occur during reductions in inward-rectifying potassium current (IKir) associated with dendritic depolarization. Thus, in addition to cholinergic reductions in transmitter release that are known to facilitate train-evoked responses, these findings emphasize the role of inhibition of Ih in the integration of synaptic inputs within the entorhinal cortex during cholinergically-induced oscillatory states, likely due to enhanced summation of excitatory postsynaptic potentials (EPSPs) induced by increases in dendritic Rin.
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5-Hydroxytrytamine (serotonin) type 3A receptors (5-HT3ARs), as the only ligand-gated ion channels in the serotonin receptor family, are known to regulate neuronal excitation and release of GABA in hippocampal interneurons. However, their physiological role in glutamatergic synaptic plasticity remains unclear. Here, we show that deletion of the 5-HT3AR gene in transgenic mice abolished N-methyl-d-aspartate (NMDA) receptor (NMDAR)-dependent long-term depression (LTD) induced by low-frequency stimulation (LFS) in hippocampal CA1 synapses in slices, whereas the metabotropic glutamate receptor (mGluR)-dependent LTD did not change in the 5-HT3AR knockout mice. ⋯ However, the deletion of 5-HT3ARs did not lead to loss of synapses and structural alteration of dendritic spines. Furthermore, the concentrations of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in the hippocampus were not affected by the deletion of 5-HT3ARs. These observations revealed an important role of 5-HT3ARs in NMDAR-dependent long-term depression, which is critical for learning behaviors.
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Tetramethylpyrazine (TMP) is an active compound extracted from the traditional Chinese medicinal herb Chuanxiong. Recently, it has been reported that TMP enhances neurogenesis, and promotes neural stem cell differentiation toward neurons. However, its molecular basis remains unknown. ⋯ We further performed chromatin immunoprecipitation (ChIP) analysis and identified that TMP enhanced the recruitment of Ac-H3 and Ac-H4 to the TopoIIβ gene promoter region. Therefore, we concluded that TMP may stimulate neuronal differentiation of SH-SY5Y cells through epigenetic regulation of TopoIIβ. These results suggest a novel molecular mechanism underlying TMP-promoted neuronal differentiation.