Neuroscience letters
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Neuroscience letters · Jan 2006
Comparative StudyNerve growth factor mediates peripheral mechanical hypersensitivity that accompanies experimental cystitis in mice.
Increased sensitivity to somatic stimuli has been noted in the presence of visceral inflammation. Cystitis was induced by intraperitoneal injection of cyclophosphamide (CYP) in female mice. Sensitivity of hind paws to mechanical stimuli was determined prior to and 4, 9 and 24 h after CYP, and sensitivity of the tail to thermal stimuli was determined prior to, 4 and 24 h after CYP treatment. ⋯ Four hours after intravesical instillation of NGF, the threshold of the hind paws to mechanical stimulation was significantly decreased, and this effect was reversed by prior treatment with NGF antiserum. This model of visceral pain causes increased sensitivity to peripheral application of mechanical stimuli. This effect is at least partially mediated by NGF, and the bladder may be the source of NGF in this process.
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Neuroscience letters · Jan 2006
Comparative StudyVisual cortex activation in late-onset, Braille naive blind individuals: an fMRI study during semantic and phonological tasks with heard words.
Visual cortex activity in the blind has been shown in Braille literate people, which raise the question of whether Braille literacy influences cross-modal reorganization. We used fMRI to examine visual cortex activation during semantic and phonological tasks with auditory presentation of words in two late-onset blind individuals who lacked Braille literacy. Multiple visual cortical regions were activated in the Braille naive individuals. ⋯ Such learning might strengthen remote connections with multisensory cortical areas. Of necessity, the Braille naive participants must attend to auditory stimulation for language. We hypothesize that learning to attend to non-visual inputs probably strengthens the remaining active synapses following visual deprivation, and thereby, increases cross-modal activation of lower tier visual areas when performing highly demanding non-visual tasks of which reading Braille is just one example.
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Neuroscience letters · Jan 2006
Comparative StudyVariants in candidate ALS modifier genes linked to Cu/Zn superoxide dismutase do not explain divergent survival phenotypes.
Familial amyotrophic lateral sclerosis (ALS) accounts for 10% of all ALS cases; approximately 25% are due to mutations in the Cu/Zn superoxide dismutase gene (SOD1). In North America, SOD1(A4V) is the most common SOD1 mutation. A4V ALS cases typically have a very short survival (1-1.5 years versus 3-5 years for other dominant SOD1 mutations). ⋯ By contrast, SOD1(D90A/D90A) ALS cases have a very slow progression (>10 years), raising the reciprocal hypothesis that modifier genes linked to SOD1 ameliorate the phenotype of recessively inherited SOD1(D90A/D90A) mutations. In the present study, DNA sequencing of four genes within the haplotypic region shared in A4V and D90A ALS patients revealed 15 novel variants, but none result in changes in amino acid sequences specifically associated with SOD1(D90A/D90A) or SOD1(A4V) ALS. We conclude that mutations within coding regions of genes around the SOD1 locus are not responsible for the more aggressive and more benign natures of the SOD1(A4V) and SOD1(D90A/D90A) mutations, respectively.
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Neuroscience letters · Dec 2005
Differential expression of NMDA receptor subunits between neurons containing and not containing enkephalin in the mouse embryo spinal cord.
We transfected cultures of mouse spinal cord slices with the enhanced green fluorescent protein (GFP) gene driven by the promoter for preproenkephalin, using the particle-mediated gene transfer system adapted for small neurons in the superficial dorsal horn, and observations were made after 4-6 days in vitro. A considerable number of cells in the superficial dorsal horn were observed to express GFP fluorescence, reminiscent of the previously reported distribution of enkephalinergic neurons in the spinal cord. ⋯ These observations suggest that expression of NMDA receptor subunits is controlled differentially in distinct populations of neurochemically identified neurons in the spinal cord. Biolistic particle-mediated gene transfection seems useful for identifying neuronal phenotypes in organotypic cultures of the spinal cord.
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Neuroscience letters · Dec 2005
Comparative StudyEffect of metabotropic glutamate receptor subtype 5 antagonist, 2-methyl-6-(phenylethynyl)-pyridine on mechanosensory afferents innervating rat hind paw following inflammation.
We investigated whether the metabotropic glutamate receptor subtype 5 (mGluR5) selective antagonist, 2-methyl-6-(phenylethynyl)-pyridine (MPEP) has direct effects on primary afferent fiber responses to noxious mechanical stimulation following inflammation. Mechanosensory primary afferent fibers innervating the hind paw were recorded in naïve and complete Freunds adjuvant (CFA) inflamed rats. Following intraplantar injection of CFA, afferent fibers showed property changes including expanded receptive fields, burst firing with fast adaptive mechanical responses and a higher incidence of cold and/or heat sensitivities compared to naïve rats. ⋯ The mean ID50 value of MPEP was 6.49+/-0.43 mg/kg. In contrast to its inhibitory action in the CFA model, i.v. administration of MPEP produced only a mild reduction of mechanical responses in 3 fibers out of 11 in naïve rats. These results provide direct functional evidence that blockade of peripheral mGluR5 receptors inhibits nociceptive transmission and support previous studies demonstrating a peripheral site of action associated with the antinociceptive effect of MPEP following inflammation.