Neuroscience
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This study aimed to investigate the effects of regular treadmill exercise on nerve growth factor (NGF) expression, the improvement of cognitive function in the hippocampus of diabetic rats, and to understand the molecular mechanisms through which the relevant signaling factors act. We investigated the effects of regular treadmill exercise for 6 weeks on NGF, tyrosine kinase receptor A (TrkA), p75 receptor, phosphatidylinositol 3-kinase (PI3-K), mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase 1/2 (Erk1/2), cyclic AMP response element-binding protein (CREB), and caspase-3 protein levels; we also assessed cell survival and cognitive function. Forty male Sprague-Dawley rats were divided into four groups: (1) normal control group (NCG: n=10); (2) normal exercise group (NEG: n=10); (3) diabetes control group (DCG: n=10), and (4) diabetes exercise group (DEG: n=10). ⋯ The p-PI3-K and t-CREB protein levels significantly increased in the NEG (P<0.001 and P<0.05, respectively), whereas t-Erk1/2 significantly decreased in the DCG (P<0.01, P<0.01, respectively). p-Erk1/2 and p-CREB protein levels significantly increased in the NEG and DEG (P<0.001, P<0.001, and P<0.01, respectively). Caspase-3 protein levels significantly increased in the DCG (P<0.001). These results show that treadmill exercise improves cognitive function, increases the number of BrdU-labeled cells, and increases NGF levels, by the activation of the MAPK/Erk1/2 signaling pathway in the hippocampus of diabetic rats.
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Lamina I of the spinal dorsal horn contains neurons that project to various brain regions, and approximately 80% of these projection cells express the neurokinin 1 receptor (NK1r), the main receptor for substance P. Two populations of NK1r-immunoreactive neurons have been identified in lamina I: small weakly immunoreactive cells and large cells with strong immunolabelling [Cheunsuang O and Morris R (2000) Neuroscience 97:335-345]. The main aim of this study was to test the hypothesis that the large cells are projection neurons and that the small cells are interneurons. ⋯ Fifteen percent of these were pyramidal, but these did not differ in size from pyramidal NK1r-immunoreactive projection neurons. These results confirm that large NK1r-immunoreactive lamina I neurons are projection cells, and suggest that the small cells are interneurons. Since almost all of the NK1r-immunoreactive cells with soma size >200 microm(2) were retrogradely labelled, cells of this type can be identified as projection cells in anatomical studies.
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There is evidence of structural and functional deterioration in the brain, including the prefrontal cortex (PFC) and hippocampus, during the normal aging process in animals and humans. Extracellular matrix-associated glycoproteins, such as chondroitin sulfate proteoglycans (CSPGs), are involved in not only maintaining the structures and functions of adult neurons, but also regulating the proliferation, migration, and neurite outgrowth of neural stem cells in the brain. On the other hand, a herbal medicine, yokukansan (YKS), is used in a variety of clinical situations for treating symptoms associated with age-related neurodegenerative disorders such as Alzheimer's disease, but its pharmacological properties have not been fully understood. ⋯ Aged rats also showed a decreased number of BrdU-labeled cells in the PFC and hippocampus, and these decreases were improved by YKS treatment, which also increased the numbers in young rats. These results suggest that aging influences the microenvironment for adult and immature neurons in the brain, which may affect the proliferation and migration of neural stem/progenitor cells, and YKS has pharmacological potency for these age-related events. These findings help to understand the physiology and pathology of the aged brain and provide an anti-aging strategy for the brain.
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Glutamatergic N-methyl-d-aspartate NMDA receptors (NMDAR) are considered to play a key role in ischemia-induced damage. Long-term (hours) changes in their expression upon ischemia have been shown. Here we report short-term changes in the mRNA levels of the major hippocampal NMDAR subunits (NR1, NR2A and NR2B), as well as c-fos, in an ex vivo ischemia model using hippocampal slices. ⋯ Since OGD-induced damage has been reported to be a consequence of the increase in OGD-related glutamate release, we also analyzed NMDAR mRNA levels following increased glutamate levels in hippocampal sections in which no significant effects on NMDAR subunit mRNA levels were detected. Furthermore, we describe that the presence of MK-801 (a selective NMDAR antagonist), CNQX (a selective AMPA/kainate receptor antagonist) or their combined action in the incubation solution is able to induce a significant decrease in NMDAR expression but in these conditions the OGD does not induce further decreases in mRNA levels. We suggest that the mechanisms triggered during OGD to downregulate mRNA levels of NMDAR subunits could be the same than those induced by glutamate receptor antagonists.
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Comparative Study
Modular organization in area 21a of the cat revealed by optical imaging: comparison with the primary visual cortex.
Area 21a, located on the cat's lateral suprasylvian cortex, is considered as a higher-order cortical area. Little is known about its specific role in visual processing. In this study, the functional organization of area 21a was investigated by optical imaging of intrinsic signals and was compared to that of primary visual areas. ⋯ The mean preferred spatial frequency in area 21a was 0.30 c/deg. In contrast to area 18, no direction maps were observed in area 21a whether drifting gratings or random dot kinematograms were used. This study supports the proposal that area 21a plays a pivotal role along the ventral processing stream and is mainly involved in form processing.