Neuroscience letters
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Neuroscience letters · Nov 2000
Abnormal synaptic organization between granule cells and Purkinje cells in the new ataxic mutant mouse, pogo.
The pogo mouse is a new ataxic mutant derived from the Korean wild mouse. The pathological manifestations include difficulty in maintaining normal posture and the inability to walk straight. The ataxia becomes apparent at about 2 weeks of age. ⋯ Major difference between pogo/pogo homozygous and non-affected pogo/+ heterozygous was the synaptic organization of the molecular layer. Parallel fiber varicosities were larger than normal and a single fiber often established synaptic contacts with up to four dendritic spines of a Purkinje cell. This correlation between the presence of altered synaptic organization in the cerebellum and ataxia in pogo/pogo mutant mice warrants further investigation.
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Neuroscience letters · Oct 2000
Changes of cortical excitability in patients with upper limb amputation.
In our study we wanted to assess motor excitability in patients with upper limb amputation by means of transcranial magnetic stimulation (TMS). In 12 patients, TMS was applied using a paired pulse paradigm in order to test cortico-cortical excitability. Additional parameters of motor excitability like motor threshold and cortical silent period were also measured. ⋯ We found a significant reduction of intracortical inhibition in forearm amputees and an enhancement of intracortical facilitation in upper arm amputees on the affected side. We conclude that after upper limb amputation, changes in the activity of intracortical interneuronal circuits appear in the affected hemisphere. These changes may depend on the level of amputation, and be the base of cortical reorganization.
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Neuroscience letters · Oct 2000
Tumor necrosis factor-alpha modulates the proliferation of neural progenitors in the subventricular/ventricular zone of adult rat brain.
Little is known about the response of neural progenitors to inflammation following injuries of the central nervous system. In combination with bromodeoxyuridine (BrdU) intraperitoneally (i.p.) injected, tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine that increased ED1+ activated microglia/macrophage population at injured sites, was administrated into adult rat brains. ⋯ However, BrdU+ cells were apparently observed in the SVZ/VZ proximal to TNF-alpha injected site, and the number of BrdU+ cells increased at 6 and 24 h post injection. Since cell apoptosis was rarely found in the SVZ/VZ after TNF-alpha injection, these observations suggest that the diffusible TNF-alpha may directly and/or indirectly modulate the proliferation of neural progenitors.
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Neuroscience letters · Oct 2000
Peripheral and spinal antihyperalgesic activity of SIB-1757, a metabotropic glutamate receptor (mGLUR(5)) antagonist, in experimental neuropathic pain in rats.
Recent studies suggest a role of Group 1 metabotropic glutamate receptors in mediating the development of spinal hypersensitivity in some pain states. Here, the possible role of mGluR(5) receptors in experimental neuropathic pain elicited by ligation of spinal nerves (L(5)/L(6) spinal nerve ligation, SNL) was explored with SIB-1757, a selective mGluR(5) antagonist. SNL-induced tactile allodynia was detected by decreased paw withdrawal thresholds to probing with von Frey filaments and thermal hyperalgesia by decreased paw withdrawal latencies to radiant heat applied to the plantar aspect of the hindpaw. ⋯ These data suggest a significant modulation of thermal hyperalgesia by mGluR(5) antagonists, consistent with reports that this receptor may be associated with afferent C-fibers. The less impressive effect seen on tactile allodynia, likely to be mediated by large fiber input, suggests that the observed modulation may be related to blockade of mGluR(5)-mediated spinal sensitization. These results do not support the involvement of these receptors in modulation of acute nociception but suggest the possibility of a role for Group I mGluRs in the mediation of aspects of neuropathic pain which may be associated with C-fiber inputs.
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Neuroscience letters · Sep 2000
Vocalization thresholds related to noxious paw pressure are decreased by paradoxical sleep deprivation and increased after sleep recovery in rat.
The aim of this study was to assess the effect of paradoxical sleep deprivation (PSD) and sleep recovery on the vocalization threshold in rats submitted to a mechanical noxious stimulus. Sixteen male Wistar rats were randomly assigned in two groups: controls (n=8), paradoxical sleep deprived rats (n=8). PSD was performed using the 'inverted flower pot' technique. ⋯ In PSD group, relative to controls, vocalization thresholds increased significantly after 48, 72, and 96 h of recovery sleep periods (day 7: 378+/-24 vs. 307+/-8 g P=0.01; day 8: 384+/-27 vs. 316+/-23 g, P=0.02; day 9: 395+/-24 vs. 328+/-15 g, P=0.02). Vocalization thresholds on day 6 were not significantly different in both groups (375+/-20 vs. 324+/-24 g, P=0.08). In conclusion, experimental PSD in rats induces a significant decrease in vocalization threshold to mechanical noxious stimulus, which is totally reversed during the sleep recovery period.