Neuroscience letters
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Neuroscience letters · Jan 2012
Expression of spinal cord microRNAs in a rat model of chronic neuropathic pain.
Neuropathic pain is accompanied by significant alterations of gene expression patterns in the somatosensory nervous system. The spinal cord is particularly prone to neuroplastic changes. Since the expression of microRNAs (miRNAs) has been linked to numerous pathophysiological processes, a contribution of miRNAs to the maladaptive plasticity of the spinal cord in neuropathic pain is possible. ⋯ Members of the let-7 family as well as miR-124 belong to the group of the most highly expressed miRNAs. Induction of neuropathic pain by CCI did not lead to relevant differences in spinal miRNA expression levels compared to sham-operated animals at any studied time point. Therefore, modulation of miRNAs does not seem to contribute significantly to the changes in gene expression that cause neural plasticity in the spinal cord in this model of chronic neuropathic pain.
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Neuroscience letters · Jan 2012
Impact of the COMT Val(108/158)Met polymorphism on the mu-opioid receptor system in the human brain: mu-opioid receptor, met-enkephalin and beta-endorphin expression.
The Val(108/158)Met polymorphism of the catechol-O-methyltransferase gene (COMT) is known to interact with the function of various neuroreceptor systems in the brain. We have recently shown by post-mortem receptor autoradiography that the number of mu-opioid (MOP) receptor binding sites depends on the number of COMT Met(108/158) alleles in distinct human brain regions. We now investigated COMT Val(108/158)Met related levels of the MOP receptor protein and its endogenous ligands met-enkephalin and beta-endorphin in the human frontal cortex, thalamus and basal ganglia. ⋯ Also met-enkephalin peptide levels correlated with the genotype in this structure, with the lowest expression in COMT Met(108/158) homozygous individuals. Beta-endorphin was not detectable in the cortex, basal ganglia or thalamus, and therefore is unlikely to contribute to changes of the MOP receptor system. These results confirm the impact of the COMT Val(108/158)Met polymorphism on the MOP receptor system and may support the hypothesis of an enkephalin related turnover of MOP receptors at least in some brain structures.
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Neuroscience letters · Jan 2012
Involvement of neuronal nitric oxide synthase in cognitive impairment in isoflurane-treated rats.
The underlying causes of post-operative cognitive dysfunction (POCD) in elderly patients remain to be elucidated. In order to explore possible contributory mechanisms, we tested the effects of isoflurane anesthesia on (i) expression of hippocampal neuronal nitric oxide synthase (nNOS) and (ii) the relationship of changes in nNOS expression to cognitive dysfunction in isoflurane-treated aged rats. Our results indicate that isoflurane treatment leads to significant changes in correct reactions (F=28.35, p<0.001), initiative avoidances (F=29.33, p<0.001), and total reaction time (TRT) (F=6.99, p<0.05) of treated rats in the Y-maze test. ⋯ TRTs to complete 20 trials of the Y-maze test increased significantly 48 h after 2 h anesthesia. The number of nNOS-positive hippocampal neurons decreased 24 h after anesthesia, corresponding to an increased mean immunostaining grey-scale value. These data show that isoflurane causes a transient decrease in expression of hippocampal nNOS in aged rats during early post-anesthesia stages, and that the transient decrease of nNOS is closely correlated with cognitive impairment in isoflurane-treated aged rats.
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Neuroscience letters · Jan 2012
The anatomical characteristics of superior longitudinal fasciculus I in human brain: Diffusion tensor tractography study.
The superior longitudinal fasciculus (SLF) I is known to be involved in regulation of higher aspects of motor function. Using diffusion tensor imaging (DTI), we attempted to identify the SLF I and to investigate the anatomical characteristics of the SLF I in the human brain. We recruited 30 healthy subjects for this study. ⋯ There were no significant differences between hemispheres in terms of the FA, MD, and tract volume. We present with the anatomical characteristics of the SLF I in the human brain using DTI. We think that the methodology and results of this study would be helpful to researchers in this field.
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Neuroscience letters · Jan 2012
Increased cutaneous NGF and CGRP-labelled trkA-positive intra-epidermal nerve fibres in rat diabetic skin.
In this study we have determined the amount of Nerve Growth Factor (NGF) and the innervation density of the glabrous hindpaw skin of diabetic rats (n=4) and controls (n=3). The proportion of intra-epidermal nerve fibres (IENF) expressing the high affinity NGF receptor (trkA) and calcitonin gene-related peptide (CGRP) were also determined. Four weeks after induction of diabetes by intraperitoneal streptozotocin injection skin was analyzed for: (i) NGF content using ELISA and (ii) the innervation density of peptidergic afferents that also expressed trkA using immunocytochemistry. ⋯ As expected there was a significant reduction in IENF density in diabetic skin (2.7±1.3 fibresmm(-1)) compared to controls (6.9±1.5 fibresmm(-1); p=0.01). In diabetic rats there was no significant difference in the proportion of trkA-labelled IENF (diabetic 74±21%; control 83±15%, p=0.6), but significantly more trkA-positive IENF were also labelled by CGRP antibodies in diabetic skin compared to controls (diabetic 89±22%; control 38±2%, p=0.03). These data suggest that in diabetes the upregulation of cutaneous NGF may 'over-troph' the surviving axons, increasing CGRP labelling, which may be important in the aetiology of painful diabetic neuropathy.