Brain research
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Enhancement of the glutamatergic excitatory synaptic transmission efficacy in the FeCl3 induced epilepsy model is associated with changes in the levels of glutamate and GABA transporter proteins. This study examined the effect of levetiracetam (LEV) on glutamate overflow and glutamate/GABA transporters expression in rats with epileptogenesis induced by the amygdalar injection of 1.0 microl of 100 mM FeCl3 (epileptic rat) and in control rats receiving amygdalar acidic saline injection (non-epileptic rat). In amygdalar acidic saline injected rats, 40 mM KCl-evoked glutamate overflow was significantly suppressed by both 32 and 100 microM LEV co-perfusion. ⋯ The increased expression of EAAC-1 and the decreased expression of GTRAP3-18 in association with the up-regulation of GAT-3 due to such continual LEV administration was thus found to enhance GABA synthesis and reverse the transport of GABA both in non-epileptic and epileptic rats. The suppression of glutamate excitation and the enhancement of GABA inhibition in the rats with continual LEV administration is a result of the up-regulation of glutamate and GABA transporters with the down-regulation of GTRAP3-18. These observations together demonstrated the critical molecular mechanism of the anti-epileptic activity of LEV.
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The subthalamic nucleus receives serotonergic projections from the dorsal raphe nucleus. However, the role of serotonergic innervation in the activity of subthalamic neurons in vivo is unknown. The aim of the present work is to study the changes in the firing of subthalamic neurons in rats with 5,7-dihydroxytryptamine lesions of the dorsal raphe nucleus and rats with combined 5,7-dihydroxytryptamine lesions in the dorsal raphe nucleus and 6-hydroxydopamine lesions in the substantia nigra pars compacta by using single-unit extracellular recordings. ⋯ In rats with combined dorsal raphe nucleus and substantia nigra pars compacta lesions, the firing rate and firing pattern of subthalamic neurons did not show a significant difference compared to rats with lesions of the substantia nigra pars compacta. However, dorsal raphe nucleus and substantia nigra pars compacta lesions combined increased significantly the percentage of subthalamic neurons with burst-firing pattern compared to normal rats, while having no effect on their firing rate. These results show that the serotonergic efferent projections of the dorsal raphe nucleus significantly influence on the activity of subthalamic neurons and that the loss of dopaminergic projection by substantia nigra pars compacta lesion decreases the effect of the lesions of the dorsal raphe nucleus on subthalamic nucleus neuronal activity, suggesting that the role of the dorsal raphe nucleus may be exerted by the dorsal raphe nucleus-substantia nigra pars compacta-subthalamic nucleus pathway.
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In two recent papers, Heil et al. [Heil, M., Rolke, B., Pecchinenda, A., 2004. Automatic semantic activation is no myth: semantic context effects on the N400 in the Letter-Search task in the absence of response time effects. Psychol. ⋯ ERP analyses of task effects on semantic processing from words. Cogn. Brain Res., 23, 293-305] are largely due to differences in experimental method and procedure, rather than to the technique used for the ERP analysis.
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The effects of propofol, a short-acting general anesthetic, upon cell growth and Ca(2+) signaling in a human astrocytic cell line were examined. Exposure of cells to graded concentrations of propofol resulted in a dose-dependent decrease in cell number with an inhibitory concentration of cell viability (IC50) of 31.7+/-1.2 microM. To evaluate the changes in intracellular Ca(2+) homeostasis induced by propofol, cytoplasmic and mitochondrial Ca(2+) were measured by fluorescence imaging. ⋯ In addition, diazoxide increased mitochondrial Ca(2+) in control cells to a level comparable to propofol treated cells suggesting activation of these channels by propofol treatment. Addition of 1 muM RU-360 (a selective blocker of the mitochondrial Ca(2+) uniporter) for 30 min prior to propofol treatment restored mitochondrial and cytoplasmic Ca(2+) to control levels. These data suggest that voltage operated Ca(2+) channels, mitochondrial Ca(2+) and K(+)-ATP channels may be targets of propofol action in astrocytes.
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When two targets have to be identified in a rapid serial visual presentation (RSVP) paradigm, perception of the second target (T2) becomes significantly impaired if it is displayed 200-500 ms after the first target (T1), a phenomenon labeled as "Attentional Blink" (AB). Here we investigate 14 spider phobics and 16 controls in an RSVP paradigm with neutral T1s. T2 pictures were neutral, emotional (positive or negative) or threatening (spiders for spider phobics). ⋯ In addition, spider phobics detected spider T2s more frequently than all other T2s. Furthermore, significantly larger P300 amplitudes accompanied detection of spider T2s in the spider phobics as compared to the controls. Based on recent theoretical accounts of the AB effect, results indicate a phobia-related post-perceptual consolidation bias of threatening information in spider phobic subjects.