Neuroscience
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Animals exposed to phencyclidine (PCP) during the neonatal period have fewer GABAergic interneurons in the corticolimbic area, including the hippocampus, and exhibit abnormal behaviors after attaining maturation that correspond with schizophrenic symptoms. Since a lack of inhibitory interneurons in the hippocampus has also been reported in postmortem studies of patients with schizophrenia, the deficit may induce abnormal activity of hippocampal neurons that underlies pathological states in schizophrenia. However, it remains unclear how PCP treatment during the neonatal period affects the discharge activity of hippocampal neurons in adulthood. ⋯ Further, the number of neurons with E/E-type response was higher in the PCP-treated mice than in the saline-treated mice. Finally, the attenuation of an auditory-evoked potential component, N40, to the second click (sensory gating) was blunted in the PCP-treated mice when compared with that in the saline-treated mice. These results suggest that the neonatal administration of PCP induced a deficit of inhibitory interneurons and altered discharge activity of neurons in the hippocampal CA3 region to the paired clicks, thereby inducing the deficit in sensory gating.
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Neurotrophins like brain-derived neurotrophic factor (BDNF) promote the migration of subsets of neural progenitor cells. The mechanism by which motility is increased and the functional properties of BDNF-responsive cells are not very well known. We have used the neurosphere model, combining time-lapse microscopy, immunocytochemistry, and Ca(2+) imaging, to study the effect of BDNF on parameters such as motility and neurotransmitter responsiveness of migrating neural progenitors. ⋯ Kainate-responsive cells, denoting the expression of AMPA/kainate receptors, dominated in the outer migration layers while cells responding to (S)-3,5-dihydroxyphenylglycine (DHPG) via metabotropic glutamate receptor 5 (mGluR5) dominated in the inner migration layers. BDNF did not appreciably affect the distribution of these cells but promoted the redistribution of a small subpopulation (about 20%) of N-methyl-D-aspartate (NMDA)- and GABA-responsive cells to the outermost layers of migration. The results demonstrate that BDNF does not affect cell motility per se but alters the phasic behavior of cell movement by promoting periods of high motility in a defined subpopulation of cells which give a robust Ca(2+) response to NMDA and GABA.
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PreBötzinger complex (preBötC) neurons in the brainstem underlie respiratory rhythm generation in vitro. As a result of network interactions, preBötC neurons burst synchronously to produce rhythmic premotor inspiratory activity. Each inspiratory neuron has a characteristic 10-20 mV, 0.3-0.8 s synchronous depolarization known as the inspiratory drive potential or inspiratory envelope, topped by action potentials (APs). ⋯ We promoted the depletion of intracellular Ca(2+) stores by a transient bath application of 30 mM K(+) (high K(+)) in the continuous presence of thapsigargin or CPA. After washing out the high K(+), respiratory rhythm period and amplitude returned to baseline values. These results show that after inhibition of SERCA and depletion of intracellular Ca(2+) stores, respiratory rhythm remains substantially the same, suggesting that this source of Ca(2+) does not significantly contribute to rhythm generation in the preBötC in vitro.
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Microcirculatory dysfunction may contribute to delayed cerebral ischemia after subarachnoid hemorrhage (SAH). Using a prechiasmatic injection model, this study investigated ultrastructural changes in microvessels in brain parenchyma to determine the nature of the microthromboemboli, the involvement of nitric oxide (NO) and P-selectin in their formation, and relationship to brain injury after SAH. Brains were examined by electron microscopy (EM) and immunohistochemistry. ⋯ This correlated with decreased NO in the brain. In conclusion, SAH causes microthrombosis and constriction of arterioles, which correlates with neuronal cell death. Increased P-selectin and decreased NO suggest a mechanism for microthrombosis and arteriolar constriction.
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Glutamate homeostasis and microglia activation play an important role in the development and maintenance of neuropathic pain. So far, there has been insufficient data on the relationship between glutamate transporters and cytokines in neuropathic pain. This investigation was designed to evaluate the interaction between co-administration of ceftriaxone, a specific GLT1 activator and minocycline, a specific microglia inhibitor, on the mechanical and cold allodynia of chronic constriction injury model (CCI) in rats. ⋯ TNF-α and IL-1β increased in the spinal cord of CCI animals on days 3, 7 and 14 post-surgery. Production of studied cytokines was significantly attenuated after treatment with ceftriaxone alone and in combination with minocycline compared with control group. It is suggested that combination of these classes of drugs would be a promising approach for treatment of chronic neuropathic pain.