BackgroundSensory stimuli evoke responses in cerebellar Purkinje cells (PCs) via the mossy fiber-granule cell pathway. However, the properties of synaptic responses evoked by tactile stimulation in cerebellar PCs are unknown. The present study investigated the synaptic responses of PCs in response to an air-puff stimulation on the ipsilateral whisker pad in urethane-anesthetized mice.Methods and Main ResultsThirty-three PCs were recorded from 48 urethane-anesthetized adult (6–8-week-old) HA/ICR mice by somatic or dendritic patch-clamp recording and pharmacological methods. Tactile stimulation to the ipsilateral whisker pad was delivered by an air-puff through a 12-gauge stainless steel tube connected with a pressurized injection system. Under current-clamp conditions (I = 0), the air-puff stimulation evoked strong inhibitory postsynaptic potentials (IPSPs) in the somata of PCs. Application of SR95531, a specific GABAA receptor antagonist, blocked IPSPs and revealed stimulation-evoked simple spike firing. Under voltage-clamp conditions, tactile stimulation evoked a sequence of transient inward currents followed by strong outward currents in the somata and dendrites in PCs. Application of SR95531 blocked outward currents and revealed excitatory postsynaptic currents (EPSCs) in somata and a temporal summation of parallel fiber EPSCs in PC dendrites. We also demonstrated that PCs respond to both the onset and offset of the air-puff stimulation.ConclusionsThese findings indicated that tactile stimulation induced asynchronous parallel fiber excitatory inputs onto the dendrites of PCs, and failed to evoke strong EPSCs and spike firing in PCs, but induced the rapid activation of strong GABAA receptor-mediated inhibitory postsynaptic currents in the somata and dendrites of PCs in the cerebellar cortex Crus II in urethane-anesthetized mice.

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The disturbance in cholesterol metabolism has been considered as a cause of alzheimer's disease (AD), which dues to the oxidative damage and cell apoptosis in the brain. We aimed to investigate the toxicity and mechanism of AD-like pathology caused by cholesterol oxidation metabolite 27-hydroxycholesterol (27-OHC) in astrocyte cells. C6 cells were treated with 0, 5, 10, 20 µM 27-OHC for 24 h (h). The cell viability was monitored by using methyl thiazolyl tetrazolium test, generation of reactive oxygen species (ROS) was measured by using 2', 7'-dichlorodihydrofluorescein diacetate fluorescent probe under flow cytometry. The concentrations of 8-hydroxyl deoxyguanosine, the anti-oxidative enzymes such as total superoxide dismutase (tSOD), reduced glutathione (rGSH) and glutathione peroxidase (GSH-Px) were tested by using enzyme-linked immunosorbent assay and enzymic method, respectively. The gene and protein expression of nuclear factor E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), NAD(P)H dehydrogenase quinone 1 (NQO1) and γ-glutamylcysteine synthetase (γ-GCS) in C6 cells were detected by quantitative western blot analysis and real-time PCR analysis. Moreover, the Nrf2 expressions in both of the cytoplasm and nucleus were detected with western blot analysis, and the localization of Nrf2 was performed by immunocytochemistry and confocal microscopy. 27-OHC increased the levels of ROS and decreased the levels of tSOD, rGSH, GSH-Px in C6 cells dose-dependently. In addition, 27-OHC down regulated the expressions of Nrf2, HO-1, NQO1 and γ-GCS at both of gene and protein levels, while Nrf2 expression in the cytoplasm showed decreased trend after incubated for 24 h with 27-OHC. The cholesterol metabolite 27-OHC is toxic to C6 cells and contributed to oxidative damage via regulating the Nrf2 signaling pathway. Our results suggest that 27-OHC may represent a common pathogenic factor in AD.