Neuroscience
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KIAA2022 has been implicated as a gene responsible for expressing X-linked mental retardation (XLMR) proteins in humans. However, the functional role of KIAA2022 in the human brain remains unclear. Here, we revealed that depletion of Kiaa2022 inhibits neurite outgrowth of PC12 cells, indicating that the gene participates in neurite extension. ⋯ Subsequent immunohistochemical analysis revealed that Xpn was localized to the nucleus and cytoplasm throughout brain development. Our findings indicate that Xpn may participate in neural circuit formation during developmental stages via nuclear and cytoplasmic Xpn. Moreover, disturbances of this neuronal circuit formation may play a role in the pathogenesis of mental retardation.
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The periaqueductal gray (PAG) is part of a descending pain modulatory system that, when activated, produces widespread and profound antinociception. Microinjection of either opioids or cannabinoids into the PAG elicits antinociception. Moreover, microinjection of the cannabinoid 1 (CB1) receptor agonist HU-210 into the PAG enhances the antinociceptive effect of subsequent morphine injections, indicating a direct relationship between these two systems. ⋯ Eight percent (8%) of PAG neurons that were MOP receptor-immunoreactive (-ir) received CB1 receptor-ir appositions. Ultrastructural analysis confirmed the presence of CB1 receptor-ir somata, dendrites and axon terminals in the PAG. These results indicate that behavioral interactions between cannabinoids and opioids may be the result of cellular adaptations within PAG neurons co-expressing CB1 and MOP receptors.
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Cholinergic activities affect olfactory bulb (OB) information processing and associated learning and memory. However, the presence of intrinsic cholinergic interneurons in the OB remains controversial. As a result, morphological and functional properties of these cells are largely undetermined. ⋯ Additionally, we quantitatively determined the density of VAChT labeled cholinergic nerve fibers in various layers of the OB, as well as the intensity of VAChT immunoreactivity within the GL, suggesting primary sites of cholinergic actions. Taken together, our results provide clear evidence showing the presence of a significant number of cholinergic interneurons and that these morphologically and distributionally diverse interneurons make up complex local cholinergic networks in the OB. Thus, our results suggest that olfactory information processing is modulated by dual cholinergic systems of local interneuron networks and centrifugal projections.
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Oligodendrocytes generate large amounts of myelin by extension of their cell membranes. Though lipid is the major component of myelin, detailed lipid metabolism in the maintenance of myelin is not understood. We reported previously that miR-32 might be involved in myelin maintenance (Shin et al., 2009). ⋯ Therefore, overexpression of SLC45A3 triggers neutral lipid accumulation. Interestingly, both overexpression and suppression of SLC45A3 reduces myelin protein expression in mature oligodendrocytes and alters oligodendrocyte morphology, indicating that tight regulation of SLC45A3 expression is necessary for the proper maintenance of myelin proteins and structure. Taken together, our data suggest that miR-32 and its downstream target SLC45A3 play important roles in myelin maintenance by modulating glucose and lipid metabolism and myelin protein expression in oligodendrocytes.
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Noninvasive neural imaging has become an important tool in both applied and theoretical applications. The hemodynamic properties that are measured in functional magnetic resonance imaging (fMRI), for example, are generally used to infer neuronal characteristics. In an attempt to provide empirical data to connect the hemodynamic measurements with neural function, we have conducted previous studies in which neural activity and tissue oxygen metabolic functions are determined together in co-localized regions of the central visual pathway. ⋯ In this investigation we have used several specific spatial stimulus patterns presented to either the CRF or the surrounding region or to both areas together in order to determine spatial response patterns. Within the CRF, we find that neural and metabolic responses sum in a nonlinear fashion but changes in these two measurements are closely coupled. For stimuli that extend beyond the CRF, neural activity is generally reduced while oxygen response exhibits uncoupled changes.