Neuroscience
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The dose-limiting side effect of the anti-neoplastic agent, paclitaxel, is a chronic distal symmetrical peripheral neuropathy that produces sensory dysfunction (hypoesthesia and neuropathic pain) but little or no distal motor dysfunction. Similar peripheral neuropathies are seen with chemotherapeutics in the vinca alkaloid, platinum-complex, and proteasome inhibitor classes. Studies in rats suggest that the cause is a mitotoxic effect on axonal mitochondria. ⋯ Paclitaxel evoked a significant increase in the incidence of swollen and vacuolated mitochondria in the myelinated and unmyelinated sensory axons of the dorsal root (as seen previously in the peripheral nerve) but not in the motor axons of the ventral root. Stimulated mitochondrial respiration in the dorsal root was significantly depressed in paclitaxel-treated animals examined 2-4 weeks after the last injection, whereas respiration in the ventral root was normal. We conclude that the absence of motor dysfunction in paclitaxel-evoked peripheral neuropathy may be due to the absence of a mitotoxic effect in motor neuron axons, whereas the sensory dysfunction may be due to a mitotoxic effect resulting from the primary afferent neuron's cell body being exposed to high and persistent levels of paclitaxel.
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Spinal cord stimulation (SCS) is used clinically to treat neuropathic pain states, but the precise mechanism by which it attenuates neuropathic pain remains to be established. The profile of afferent fiber activation during SCS and how it may correlate with the efficacy of SCS-induced analgesia are unclear. After subjecting rats to an L5 spinal nerve ligation (SNL), we implanted a miniature quadripolar electrode similar to that used clinically. ⋯ Results showed that three consecutive days of SCS treatment (50 Hz, 0.2 ms, 30 min, 80-90% of MoT), but not sham stimulation, gradually alleviated mechanical hypersensitivity in SNL rats. The MoT obtained in the animal behavioral study was significantly less than the Aα/β-threshold of the compound AP determined during electrophysiological recording, suggesting that SCS could attenuate mechanical hypersensitivity with a stimulus intensity that recruits only a small fraction of the A-fiber population in SNL rats. Although both the MoT and compound AP threshold were similar between responders and nonresponders, the size of the compound AP waveform at higher stimulation intensities was larger in the responders, indicating a more efficient activation of the dorsal column structure in responders.
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Pregnant rats were treated daily with 1 g/L of L-glutamate in their drinking water during pregnancy and/or lactation. The effect on adenosine A₁ receptor (A₁R) and A(2A) receptor (A(2A)R) in brains from both mothers and 15-day-old neonates was assayed using radioligand binding and real time PCR assays. Mothers receiving L-glutamate during gestation, lactation, and throughout gestation and lactation showed a significant decrease in total A₁R number (water+water, 302±49 fmol/mg; L-glutamate+water, 109±11 fmol/mg, P<0.01; water+L-glutamate, 52±13 fmol/mg, P<0.01; L-glutamate+L-glutamate, 128±33 fmol/mg, P<0.05). ⋯ Concerning adenosine A(2A)R, radioligand binding assays revealed that Bmax parameter was significantly increased in male and female neonates exposed to L-glutamate during lactation (male neonates: water+water, 214±23 fmol/mg; water+L-glutamate, 581±49 fmol/mg; P<0.01; female neonates: water+water, 51±10 fmol/mg; water+L-glutamate, 282±52 fmol/mg; P<0.05). No variations were found in mRNA level coding adenosine A(2A)R in maternal or neonatal brain. In summary, long-term L-glutamate treatment during gestation and lactation promotes a significant down-regulation of A₁R in whole brain from both mother and neonates and a significant up-regulation of A(2A)R in neonates exposed to L-glutamate during lactation.
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Recent studies have shown that autophagy upregulation may be a tractable therapeutic intervention for clearing the disease-causing proteins, including α-synuclein, ubiquitin, and other misfolded or aggregated proteins in Parkinson's disease (PD). In this study, we explored a novel pharmacotherapeutic approach to treating PD by utilizing potential autophagy enhancers valproic acid (VPA) and carbamazepine (CBZ). ⋯ Moreover, pretreatment with the autophagy inhibitor chloroquine (Chl, 10 μM) remarkably strengthened rotenone toxicity in these cells. Our results suggest that VPA and CBZ, the most commonly used anti-epilepsy and mood-stabilizing medications with low-risk and easy administration might be potential therapeutics for PD.
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Sixteen healthy subjects took part in this event-related potentials (ERPs) study aimed at investigating the neural response of the taste-visual cross-modal pairing. An interference effect was observed at the behavioral level: the mismatched condition was performed more slowly than the matched condition. ⋯ Dipole source analysis of the difference wave (mismatched minus matched) indicated that two generators localized in prefrontal cortex (PFC) and posterior cingulate cortex (PCC) contributed to this cross-modal interference effect. These results provided the electrophysiological evidence of interference during the extraction of taste information from memory and conflict control during the incongruent taste-visual information processing.