Neuroscience
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To elucidate the mechanism of orphanin FQ on neuroimmune modulation, the relationship between orphanin FQ and interleukin-1beta in the rat CNS in vivo and in vitro was investigated. In our experiments, it was found that orphanin FQ and interleukin-1beta mRNA transcripts showed a similar distribution in cerebral cortex, hippocampus and hypothalamus. By using the in situ hybridization technique, down-regulation of interleukin-1beta mRNA transcripts by central administration of orphanin FQ was further identified in the traumatic animal model. ⋯ When analyzed by reverse transcription-polymerase chain reaction, interleukin-1beta gene expression was observed to be enhanced and inhibited in primary neuron and microglial cell cultures exposed to orphanin FQ respectively. Interleukin-1beta gene expression in astrocyte cultures was not affected by treatment with orphanin FQ. Our findings suggest that the neuroimmune function of orphanin FQ might be dependent on interleukin-1beta derived from microglia, and the interaction between microglia and neurons.
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Glutamate-gated ion channels are widely expressed in neurons where they serve a host of cellular functions. An appealing, but yet unexplored, way to delineate the functions of particular glutamate receptor subtypes is to direct the expression of dominant-negative and gain-of-function mutant subunits. We tested the ability of two dominant-negative subunits, an alpha-amino-3-hydroxy-5-methyl-isoxazolproprionic acid receptor subunit and a kainate receptor subunit, to silence recombinant and neuronal glutamate receptors. ⋯ When expressed in cerebellar granule cells, the dominant-negative subunits silenced native channels in a subtype-specific fashion. Immunocytochemical staining of control and transfected neurons, as well as studies with a gain-of-function glutamate receptor-1 mutant, indicated that the mutant subunits were expressed at levels roughly equal to the total abundance of related native subunits, and both dominant-negatives suppressed native channel expression 60-65% when tested 24 h post-transfection. If co-assembly of the mutant subunits with related native subunits is combinatorial, this level of suppression gives receptor half-lives of approximately 20 h.