Brain research
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Subthreshold membrane potential oscillations (SMPO) in the injured dorsal root ganglion (DRG) neurons are involved in the generation of spontaneous activity, which can directly evoke neuropathic pain. Nerve injury usually triggers the synthesis of large quantities of membrane protein in nerve injured DRG neurons. Membrane proteins are glycosylated by addition of sugars, especially negatively charged sialic acid residues, which may depolarize the resting membrane potential (Vm), open voltage-gated channels in injured neurons, and cause spontaneous activity. ⋯ Topical application of neuraminidase to selectively remove sialic acid residues on the extracellular membrane normalized the depolarized Vm and inhibited both spontaneous and evoked SMPO. However, application of Ca(2+), Mg(2+), Mn(2+) or neuraminidase had no effect on excitability and Vm in normal neurons. The results demonstrated that the increase in negatively charged sialic acid residues on the extracellular membrane of neuronal somata is a critical factor in the generation of SMPO and hyperexcitability in injured sensory neurons.
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This paper studied the effects of crocin, a pharmacologically active component of Crocus sativus L., on ischemia/reperfusion (I/R) injury in mice cerebral microvessels. Transient global cerebral ischemia (20 min), followed by 24 h of reperfusion, significantly promoted the generation of nitric oxide (NO) and malondialdehyde (MDA) in cortical microvascular homogenates, as well as markedly reduced the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-px) and promoted the activity of nitric oxide synthase (NOs). Reperfusion for 24 h led to serous edema with substantial microvilli loss, vacuolation, membrane damage and mitochondrial injuries in cortical microvascular endothelial cells (CMEC). ⋯ Pretreatment with crocin markedly inhibited oxidizing reactions and modulated the ultrastructure of CMEC in mice with 20 min of bilateral common carotid artery occlusion (BCCAO) followed by 24 h of reperfusion in vivo. Furthermore, crocin inhibited GRK2 translocation from the cytosol to the membrane and reduced ERK1/2 phosphorylation and MMP-9 expression in cortical microvessels. We propose that crocin protects the brain against excessive oxidative stress and constitutes a potential therapeutic candidate in transient global cerebral ischemia.
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Comparative Study
GABA-mediated oxytocinergic inhibition in dorsal horn neurons by hypothalamic paraventricular nucleus stimulation.
In anaesthetized rats, we tested whether the unit activity of dorsal horn neurons that receive nociceptive input is modulated by electrical stimulation of the hypothalamic paraventricular nucleus (PVN). An electrophysiological mapping of dorsal horn neurons at L3-L4 let us choose cells responding to a receptive field located in the toes region of the left hindpaw. Dorsal horn neurons were classified according to their response properties to peripheral stimulation. ⋯ Our results suggest that PVN stimulation inhibits nociceptive peripheral-evoked responses in WDR neurons by a descending oxytocinergic pathway mediated by GABAergic PVN-ON cells. We discuss our observation that the PVN electrical stimulation selectively inhibits Adelta and C-fiber activity without affecting Abeta fibers. We conclude that Adelta and C-fibers receive a presynaptic inhibition mediated by GABA.
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Comparative Study
Serum S100B indicates brain edema formation and predicts long-term neurological outcomes in rat transient middle cerebral artery occlusion model.
To assess the usefulness of serum S100B as a biomarker, the present study proceeded by observing serum S100B kinetics in a rat transient middle cerebral artery occlusion (MCAO) model, then assessed the correlation between serum S100B and both brain edema formation and neurological outcomes. Study results showed increases in serum S100B concentrations, peaking 48 h after MCAO. Brain water content in the ipsilateral hemisphere significantly increased from 24 h after MCAO, and reached peak value 72 h after MCAO. ⋯ Neurological outcomes were estimated in a long-term study, where a gradual recovery was observed up to 168 h after MCAO. Serum S100B 48 h after MCAO was found to show higher correlation with neurological score 168 h after MCAO than those 48 h after MCAO. These findings suggest that serum S100B is an effective biomarker in predicting both extent of brain edema and long-term neurological outcomes in a rat transient MCAO model.
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The present study examines the functional and anatomical underpinnings of egocentric and allocentric coding of spatial coordinates. For this purpose, we set up a functional magnet resonance imaging experiment using verbal descriptions of spatial relations either with respect to the listener (egocentric) or without any body-centered relations (allocentric) to induce the two different spatial coding strategies. We aimed to identify and distinguish the neuroanatomical correlates of egocentric and allocentric spatial coding without any possible influences by visual stimulation. ⋯ Furthermore, bilateral hippocampal involvement was observed during allocentric, but not during egocentric spatial processing. Our results demonstrate that the processing of egocentric spatial relations is mediated by medial superior-posterior areas, whereas allocentric spatial coding requires an additional involvement of right parietal cortex, the ventral visual stream and the hippocampal formation. These data suggest that a hierarchically organized processing system exists in which the egocentric spatial coding requires only a subsystem of the processing resources of the allocentric condition.