Neuroscience
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Transient receptor potential melastatin 8 (TRPM8) is activated by innocuous cool and noxious cold and plays a crucial role in cold-induced acute pain and pain hypersensitivity. To help understand the mechanism of TRPM8-mediated cold perception under normal and pathologic conditions, we used light microscopic immunohistochemistry and Western blot analysis in mice expressing a genetically encoded axonal tracer in TRPM8-positive (+) neurons. We investigated the coexpression of TRPM8 and vesicular glutamate transporter 1 (VGLUT1) and VGLUT2 in the trigeminal ganglion (TG) and the dental pulp before and after inducing pulpal inflammation. ⋯ TRPM8+ axons were dense in the pulp horn and peripheral pulp and also frequently observed in the dentinal tubules. Following pulpal inflammation, the proportion of VGLUT2+ and of VGLUT2+/TRPM8+ neurons increased significantly, whereas that of TRPM8+ neurons remained unchanged. Our findings suggest the existence of VGLUT2 (but not VGLUT1)-mediated glutamate signaling in TRPM8+ neurons possibly underlying the cold-induced acute pain and hypersensitivity to cold following pulpal inflammation.
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Non-physical balance training has demonstrated to be efficient to improve postural control in young people. However, little is known about the potential to increase corticospinal excitability by mental simulation in lower leg muscles. Mental simulation of isolated, voluntary contractions of limb muscles increase corticospinal excitability but more automated tasks like walking seem to have no or only minor effects on motor-evoked potentials (MEPs) evoked by transcranial magnetic stimulation (TMS). ⋯ The current results demonstrate that corticospinal excitability during mental simulation of balance tasks is influenced by both the type of mental simulation and the task difficulty. As H-reflexes and background EMG were not modulated, it may be argued that changes in excitability of the primary motor cortex were responsible for the MEP modulation. From a functional point of view, our findings suggest best training/rehabilitation effects when combining MI with AO during challenging postural tasks.
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Previous studies have shown that glial cell line-derived neurotrophic factor (GDNF) exerts significant neuroprotective effects on substantia nigra (SN) neurons in the rat 6-hydroxydopamine (6-OHDA) model of Parkinson's disease (PD). In this study we used enzyme-linked immunosorbent assay (ELISA) to determine GDNF brain levels and distribution to target regions (i.e. striatum and SN) following intranasal administration of GDNF at different time points after administration. Brain levels increased significantly within 1h following a single 50-μg dose of GDNF in a liposomal formulation, returning to baseline by 24h. ⋯ In a third study, autoradiography was performed on brain sections taken 1h after intranasal (125)I-labeled GDNF. Radioactivity was detected throughout the brain along the rostral-to-caudal axis, indicating that nasally administered GDNF can reach target areas. Collectively, these results demonstrate that intranasal administration of GDNF in liposomes or PBS achieves significant increases in GDNF in target brain areas, supporting use of intranasal administration as a non-invasive means of delivering GDNF to the brain to protect dopamine neurons and arrest disease progression in PD.
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Brain-derived neurotrophic factor (BDNF) plays a key role in neuronal development, synaptic plasticity, and the central control of energy homeostasis. Peripheral metabolic signals such as leptin and glucose regulate hypothalamic BDNF gene expression. However, the effects of long-term hyperglycemia and/or hyperinsulinemia on BDNF mRNA levels in the hypothalamus and other brain regions where BDNF regulates physiological functions have not been investigated. ⋯ Plasma BDNF concentrations were not changed by any of the treatments. Our results suggest that hyperinsulinemia alone does not affect BDNF mRNA expression in the hypothalamus, hippocampus, or pituitary. Our study is the first to distinguish that within the hypothalamus, prolonged high glucose levels in non-fasted rats regulates BDNF gene expression in a brain nuclei-specific fashion.
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Effects of the long-term use of antiepileptic drugs (AEDs) on the brains of patients with epilepsy have been previously reported. The aim of this study was to determine the rapid brain structure remodeling induced by single-dose intravenous AED administration that rules out the potential effects of epilepsy. ⋯ Single-dose intravenous administration of a level of VPA or LEV that mimics clinical use is associated with rapid and reversible VBM-detected GMV or WMV alterations in rhesus monkeys. This finding may provide new insights into the understanding of AED-induced brain structure remodeling and may contribute to our understanding of the brain-level mechanisms and targets of AED action.