Brain research
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Programmed cell death (apoptosis) in the inner ear of senescence-accelerated mouse was identified using specific labeling of fragmented DNA (the TUNEL method). In spite of some inter-individual differences, the apoptotic cells were predominantly found in the phylogenetically newer part of the inner ear, the cochlea and the saccules. ⋯ In the cochlea, positive staining was detected in inner and outer hair cells, pillar cells, Deiters' cells, interdental cells, the stria vascularis (marginal cells, intermediate cells, basal cells), and cells in Reissner's membrane. The present results suggest that age-related cell death, which may cause hearing impairment and dysequilibrium, is due to apoptosis occurring in the inner ear.
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Dextrorphan, but not dextromethorphan, exerts weak antidystonic effects in mutant dystonic hamsters.
The effects of dextromethorphan and its metabolite dextrorphan on severity of dystonia were examined in mutant dystonic hamsters, an animal model of idiopathic paroxysmal dystonia, in which recent examinations have shown antidystonic effects of selective N-methyl-D-aspartate (NMDA) receptor antagonists. Dextromethorphan and dextrorphan are non-competitive NMDA receptor antagonists which additionally exhibit affinity for sigma receptors. Dextrorphan (20 and 40 mg/kg i.p.) significantly retarded the progression of dystonia at the higher dose, whereas dextromethorphan (20, 40, 60 mg/kg i.p.) failed to exert any antidystonic effects even at high doses which caused severe effects. The lack of antidystonic efficacy of dextromethorphan may be related to its higher affinity to sigma receptors compared with dextrorphan.
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The capacity to sense changes in the concentrations of extracellular ions is an important function in several cell types. For example, hormone secretion by parathyroid cells and thyroid C-cells is primarily regulated by the level of extracellular ionized calcium (Ca2+). ⋯ Particularly high numbers of CaR expressing cells were found in regions associated with the regulation of fluid and mineral homeostasis, most notably the subfornical organ. These data suggest that the capacity to detect changes in extracellular Ca2+ concentrations may have important functional consequences in several neural systems.
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Few clinical or experimental studies have carried out systematic investigations of cutaneous and deep sensibility in areas with referred muscle pain. Therefore, no clear signs of increased or decreased psychophysical responses to various somatosensory stimuli are found in referred pain areas. In the present study, a total of 7.1 ml 5% hypertonic saline was infused over 900 s into the m. tibialis anterior of 11 subjects. ⋯ After the period with referred pain, a considerably decreased response to single and repeated, electrical stimuli (P < 0.05) was present together with significantly increased responses to contact heat stimuli at 40 degrees C and radiant heat stimuli at 75% of PT intensity (P < 0.05). The present results suggest that ongoing muscle pain can cause modality-specific (and bi-directional) sensory changes in the referred pain area. This could explain why previous studies have reported both decreased and increased responses in referred pain areas.