Neuroscience
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Schwann cells line nerve fibers in the peripheral nervous system (PNS) and synthesize myelin. In addition, they support neuronal survival, neurite growth and regeneration. In dissociated cultures of postnatal mouse spiral ganglia, regenerating neurites spontaneously associate with Schwann cells. ⋯ After 24 h in vitro, cultures were >85% Schwann cells. Nucleofection of purified Schwann cells with pMax-green fluorescent protein (pMax-GFP) plasmid, or with pEGFP-C-vimentin plasmid returned >45% transfection efficiency. These methods will allow the in-depth characterization of cochlear Schwann cells and an evaluation of their biochemical, functional, and genetic mechanisms that may promote neurite growth from the spiral ganglion.
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Parkinsonian impairment correlates with spatially extensive subthalamic oscillatory synchronization.
The local strength of pathological synchronization in the region of the subthalamic nucleus (STN) is emerging as a possible factor in the motor impairment of Parkinson's Disease (PD). In particular, correlations have been repeatedly demonstrated between treatment-induced suppressions of local oscillatory activity in the beta frequency band and improvements in motor performance. However, a mechanistic role for beta activity is brought into question by the difficulty in showing a correlation between such activity at rest and the motor deficit in patients withdrawn from medication. ⋯ Phase coherence could account for up to ∼25% of the variance in motor scores between sides and patients. These new data suggest that the strength of spatially extended oscillatory synchronization, as well as the strength of local synchronization, may be worthwhile incorporating into modelling studies designed to inform surgical targeting, post-operative stimulation parameter selection and closed-loop stimulation regimes in PD. In addition, they strengthen the link between pathological synchronization and the different motor features of Parkinsonism.
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We wanted to determine whether movement planning followed Fitts' law by investigating the relationship between movement planning and movement performance in experienced dancers executing a typical classical ballet step in which the big toe was pointed to targets at different distances and of different widths so as to obtain several indices of difficulty (ID). Movement time, velocity and variability at the target were the variables of movement performance kinematics; movement planning was evaluated by analysis of anticipatory postural adjustments (APAs) to assess their modulation at different IDs. ⋯ APA magnitude scaled with movement velocity, while APA duration was sensitive to the amplitude-to-accuracy ratio following the ID for movements performed in the shortest time interval when on-line feedback control is probably not available. Here we show that timing of muscle activation acts as an independent central command that triggers fine-tuning for speed-accuracy trade-off.
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Sensitization to mechanical stimuli is important in most pain syndromes. We evaluated the populations of nociceptors mediating mechanical hyperalgesia and those mediating mu-opioid receptor (MOR) and delta-opioid receptor (DOR) agonist-induced inhibition of hyperalgesia, in the rat. We found that: (1) intradermal injection of both the endogenous ligand for the Ret receptor, glia-derived growth factor (GDNF), and the ligand for the tropomyosin receptor kinase A (TrkA) receptor, nerve growth factor (NGF)-which are present on distinct populations of nociceptors-both produce mechanical hyperalgesia; (2) DOR agonist 4-[(R)-[(2S,5R)-4-allyl-2,5-dimethylpiperazin-1-yl](3-methoxyphenyl)methyl]-N,N-diethylbenzamide (SNC) but not MOR agonist [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO) inhibit GDNF-induced hyperalgesia; (3) both DAMGO and SNC inhibit NGF hyperalgesia, even in rats pretreated with isolectin B4 (IB4)-saporin, a toxin that destroys IB4-binding neurons; (4) co-administration of low doses of DAMGO and SNC produce enhanced analgesia, and; (5) repeated administration of DAMGO produces cross-tolerance to the analgesic effect of SNC. These findings demonstrate that, most nociceptors have a role in mechanical hyperalgesia, only the DOR agonist inhibits GDNF hyperalgesia, and MOR and DOR are co-localized on a functionally important population of TrkA-positive nociceptors.
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A growing interest was recently focused on the use of Botulinum neurotoxin serotype A (BoNT/A) for fighting pain. The aim of this study was to investigate the effects of BoNT/A on neuropathic pain. It was observed that BoNT/A is able to counteract neuropathic pain induced by chronic constriction injury (CCI) to the sciatic nerve both in mice and in rats. ⋯ The behavioral improvement was accompanied by structural modifications, as revealed by the expression of cell division cycle 2 (Cdc2) and growth associated protein 43 (GAP-43) regeneration associated proteins, investigated by immunofluorescence and Western blotting in the sciatic nerve, and by the immunofluorescence expression of S100β and glial fibrillary acidic protein (GFAP) Schwann cells proteins. In conclusion, the present research demonstrate long-lasting anti-allodynic and anti-hyperalgesic effects of BoNT/A in animal models of neuropathic pain together with an acceleration of regenerative processes in the injured nerve, as evidenced by both behavioral and immunohistochemistry/blotting analysis. These results may have important implications in the therapy of neuropathic pain.