Experimental neurology
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Experimental neurology · Nov 2004
Pyridoxine-induced toxicity in rats: a stereological quantification of the sensory neuropathy.
Excess ingestion of pyridoxine (vitamin B6) causes a severe sensory neuropathy in humans. The mechanism of action has not been fully elucidated, and studies of pyridoxine neuropathy in experimental animals have yielded disparate results. ⋯ The present study used design-based stereological techniques in conjunction with electrophysiological measures to quantify the morphological and physiological changes that occur in the DRG and the distal myelinated axons of the sciatic nerve following pyridoxine intoxication. This combined stereological and electrophysiological method demonstrates a general approach that could be used for assessing the correlation between pathophysiological and functional parameters in animal models of toxic neuropathy.
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Experimental neurology · Nov 2004
Combination therapy of moderate hypothermia and thrombolysis in experimental thromboembolic stroke--an MRI study.
Thrombolysis (T) is limited by reperfusion-associated injury and the short therapeutic window after stroke onset. The present study investigates whether hypothermia alone or in combination with thrombolysis has beneficial effects after experimental thromboembolic stroke. Wistar rats (n = 60) were subjected to thromboembolic occlusion (TE) of the middle cerebral artery (MCA). ⋯ These data indicate that hypothermia improves survival and decreases infarct volume. However, there were no significant differences between the use of rt-PA alone or in combination with hypothermia. Further studies are needed to confirm these effects, also several days after stroke onset.
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Experimental neurology · Nov 2004
Impaired axonal transport and altered axolemmal permeability occur in distinct populations of damaged axons following traumatic brain injury.
Traumatic axonal injury (TAI) evolves within minutes to hours following traumatic brain injury (TBI). Previous studies have identified axolemmal disruption and impaired axonal transport (AxT) as key mechanisms in the evolution of TAI. While initially hypothesized that axolemmal disruption culminates in impaired AxT, previous studies employed single-label methodologies that did not allow for a full determination of the spatial-temporal relationships of these two events. ⋯ These studies confirm that axolemmal disruption and impaired AxT occur as distinct non-related events early in the pathogenesis of TAI. Further, these studies provide evidence that the process of impaired axonal transport and subsequent axonal disconnection leads to delayed axolemmal instability, rather than proceeding as a consequence of initial axolemmal failure. This finding underscores the need of multiple approaches to fully assess the axonal response to TBI.
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Experimental neurology · Oct 2004
Progesterone and allopregnanolone reduce inflammatory cytokines after traumatic brain injury.
Following a traumatic brain injury (TBI), the excessive release of interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha) is a major cause of cerebral edema, which, in turn, can cause permanent neuronal loss and cognitive deficits in laboratory rats. This study examined the changes in expression of the proinflammatory cytokines IL-1beta and TNF-alpha after progesterone (8 mg/kg) or allopregnanolone (4 mg/kg) treatment in brain-injured rats at 3, 8, and 12 h and 6 days post-injury. Adult male rats received either bilateral prefrontal cortical contusion or sham surgery. ⋯ At 8 and 12 h post-injury, IL-1beta and TNF-alpha gene expression in injured rats was still elevated compared to shams. By the sixth day post-injury, cytokine expression was back to the level of intact rats. We conclude that progesterone and allopregnanolone may attenuate the production of proinflammatory cytokines early after TBI, and this may be one mechanism by which progesterone and allopregnanolone reduce cerebral edema and promote functional recovery from TBI.
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Experimental neurology · Oct 2004
Rhythm-specific pharmacological modulation of subthalamic activity in Parkinson's disease.
The subthalamic nucleus (STN) has a key role in the pathophysiology of Parkinson's disease and is the primary target for high-frequency deep brain stimulation (DBS). The STN rest electrical activity in Parkinson's disease, however, is still unclear. Here we tested the hypothesis that pharmacological modulation of STN activity has rhythm-specific effects in the classical range of EEG frequencies, below 50 Hz. ⋯ Power changes elicited by levodopa and apomorphine at low frequencies and in the beta range were not correlated, whereas changes in the alpha band, which were globally not significant, correlated with the beta rhythm (namely, low beta: 13-20 Hz). In conclusion, in the human STN, there are at least two rhythms below 50 Hz that are separately modulated by antiparkinsonian medication: one at low frequencies and one in the beta range. Multiple rhythms are consistent with the hypothesis of multiple oscillating systems, each possibly correlating with specific aspects of human STN function and dysfunction.