Neuroscience
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Microglia, the innate immune cells of the brain, regulate brain development through many processes such as synaptic pruning, supporting cell genesis and phagocytosing living and dying cells. There are sex differences in these same developmental processes throughout the brain, thus microglia may contribute to brain sex differences. We examined whether microglia support a known sex difference in neonatal hippocampal neurogenesis and whether juvenile hippocampal neurogenesis was impacted by the loss of neonatal microglia. ⋯ We also sought to determine whether there was a sex difference in the number of progenitor cells in the dentate gyrus in the neonatal period. We found no sex differences in the number of progenitor cells. Overall, these studies show that microglia are important for regulating region-specific sex differences in cell genesis in the developing brain.
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We investigated the effect of full and partial mechanical reperfusion on MMP-9 expression in rat brain following middle cerebral artery occlusion, mimicking mechanical thrombectomy. Using percentage hemispheric lesion volume and oedema as measures, partial reperfusion reduced extent of brain damage caused by MCA occlusion, but the protective effect was less pronounced than with complete reperfusion. Using ELISA quantification in fresh frozen tissue, confirmed by immunofluorescence in perfusion fixed tissue, increased MMP-9 expression was observed in infarcted tissue. ⋯ MMP-9 expression was evident in microvessels and in neuronal cell bodies of affected tissue. This study shows that MMP-9 brain levels are reduced relative to the extent of reperfusion. These observations suggest targeting early increases in MMP-9 expression as a possible neuroprotective therapeutic strategy and highlight the rat MCA occlusion model as an ideal model in which to study candidate therapeutics.
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Cortical slow rhythmic activity, a hallmark of deep sleep, is observed under urethane anesthesia. Synchronized fluctuations of the membrane excitability of a large neuronal population are reflected in the extracellular Local Field Potential (LFP), as high-amplitude slow (∼1 Hz) oscillations (SO). The SO-phase indicates the presence (Up) or absence (Down) of neuronal spiking. ⋯ The LC-DES applied during Down-phase caused a rapid Down-to-Up transition in 81.5% of trials. The LC-DES was more effective at a higher frequency, but not at a higher current. Our results suggest that transient NA release, coupled to SO, may promote synaptic plasticity and memory consolidation by sustaining a depolarized state in the mPFC neurons.