Alteration of striatal dopaminergic function induced by glioma development: a microdialysis and immunohistological study in the rat striatum

Identification of dysregulated miRNAs and their regulatory signature in glioma patients using the partial least squares method

Using microarray data, the present study identified differentially expressed microRNAs (miRNAs) and evaluated their regulatory characteristics in high-grade glioma patients, with the aim to further the understanding into the underlying etiology of the condition. Previously, studies have generally implemented regression or variance analysis, which ignores various background biological factors. However, in the present study, analysis was performed with microarray data collected from the Gene Expression Omnibus database using a partial least squares-based method, which is more sensitive in handling microarray data. Among the six identified differentially expressed miRNAs, hsa-miR-21 and hsa-miR-612 have been previously reported to be associated with glioma. In addition, the remaining miRNAs, hsa-miR-4680, hsa-miR-1908, hsa-miR-4656 and hsa-miR-4467, may also contribute to glioma progression since they are all associated with the tumorigenesis of other types of cancer. Moreover, the expression levels of hsa-miR-1908, hsa-miR-4656 and hsa-miR-4680 have been identified to significantly correlate with the survival rate. Enrichment analysis of the dysregulated target genes revealed that the selected miRNAs primarily affect biological processes in the nervous system and the protein phosphorylation process. Therefore, the results may offer a new understanding into the pathogenesis of high-grade glioma.

Microelectrodes with gold nanoparticles and self-assembled monolayers for in vivo recording of striatal dopamine

Electrochemical determination of in vivo dopamine (DA) using implantable microelectrodes is essential for monitoring the DA depletion of an animal model of Parkinson's disease (PD), but faces substantial interference from ascorbic acid (AA) in the brain area due to similar electroactive characteristics. This study utilizes gold nanoparticles (Au-NPs) and self-assembled monolayers (SAMs) to modify platinum microelectrodes for improving sensitivity and specificity to DA and alleviating AA interference. With appropriate choice of ω-mercaptoalkane carboxylic acid chain length, our results show that a platinum microelectrode coated with Au-NPs and 3-mercaptopropionic acid (MPA) has approximately an 881-fold specificity to AA. During amperometric measurements, Au-NP/MPA reveals that the responsive current is linearly dependent on DA over the range of 0.01-5 μM with a correlation coefficient of 0.99 and the sensitivity is 2.7-fold that of a conventional Nafion-coated electrode. Other important features observed include fast response time (below 2 s), resistance to albumin adhesion and low detection limit (7 nM) at a signal to noise ratio of 3. Feasibility of in vivo DA recording with the modified microelectrodes is verified by real-time monitoring of electrically stimulated DA release in the striatum of anesthetized rats with various stimulation parameters and administration of a DA uptake inhibitor. The developed microelectrodes present an attractive alternative to the traditional options for continuous electrochemical in vivo DA monitoring.

Controlled cortical impact injury influences methylphenidate-induced changes in striatal dopamine neurotransmission

Traumatic brain injury features deficits are often ameliorated by dopamine (DA) agonists. We have previously shown deficits in striatal DA neurotransmission using fast scan cyclic voltammetry after controlled cortical impact (CCI) injury that are reversed after daily treatment with the DA uptake inhibitor methylphenidate (MPH). The goal of this study was to determine how a single dose of MPH (5 mg/kg) induces changes in basal DA and metabolite levels and with electrically evoked overflow (EO) DA in the striatum of CCI rats. MPH-induced changes in EO DA after a 2-week daily pre-treatment regime with MPH was also assessed. There were no baseline differences in basal DA or metabolite levels. MPH injection significantly increased basal [DA] output in dialysates for control but not injured rats. Also, MPH injection increased striatal peak EO [DA] to a lesser degree in CCI (176% of baseline) versus control rats (233% of baseline). However, daily pre-treatment with MPH resulted in CCI rats having a comparable increase in EO [DA] after MPH injection when compared with controls. The findings further support the concept that daily MPH therapy restores striatal DA neurotransmission after CCI.