Brain research
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Numerical processing involves either number magnitude processing, which has been related to spatial abilities and relies on superior parietal regions, or arithmetic fact retrieval, which has been related to verbal abilities and involves the inferior parietal lobule. Since men score better in spatial and women in verbal tasks, we assume that women have advantages in fact retrieval, while men have benefits in number magnitude processing. According to findings on menstrual cycle variations in spatial and verbal abilities, fact retrieval should improve during the luteal phase and magnitude processing during the follicular phase. ⋯ In men and women in their luteal phase, error rates were higher and deactivation of the medial prefrontal cortex and the bilateral inferior parietal lobules was stronger for non-multiplicative compared to multiplicative items (positive multiplicativity effect), while in the follicular phase women showed higher error rates and stronger deactivation in multiplicative compared to non-multiplicative items (negative multiplicativity effect). Thus, number magnitude processing improves, while arithmetic fact retrieval impairs during the follicular phase. While a female superiority in arithmetic fact retrieval could not be confirmed, we observed that sex differences are significantly modulated by menstrual cycle phase.
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Endothelin and its receptors have long been considered therapeutic targets in the treatment of ischemic stroke. Recent studies indicate that ET(B) receptors may provide both vasodilatation and neuroprotection. The purpose of this study was to determine the effect of selectively activating the ET(B) receptors following permanent middle cerebral artery occlusion in rats. ⋯ Animals pretreated with BQ788 showed similar oxidative stress damage as those in the vehicle-treated group. No significant difference was observed in ET(B) receptor levels in any of the groups. The present study demonstrates that ET(B) receptor activation may be a novel neuroprotective therapy in the treatment of focal ischemic stroke.
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Comparative Study
Sex differences in effects of excitotoxic spinal injury on below-level pain sensitivity.
Effects of excitotoxic injury to the thoracic gray matter on sensitivity to below-level nociceptive stimulation were evaluated for female and male Long-Evans rats. Operant escape and lick/guard (L/G) reflex responses to thermal stimulation were evaluated before and for 13-15 weeks after: 1) injections of quisqualic acid (QUIS) into the thoracic gray matter (T8-9), 2) laminectomy and spinal exposure and penetration without injection (sham) or 3) no surgical procedure (control). L/G responding to heat stimulation (44 °C) was unaffected for females and males following thoracic QUIS injections. ⋯ This selective effect is indicative of altered sympathetic activation by the thoracic injections. The effect of sham surgery suggests that female rats are vulnerable to ischemic injury during exposure and manipulation of the spinal cord. Escape from nociceptive heat and cold sensitivity of control males and females was unchanged over 13-15 weeks of testing.
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The pathogenesis of neuropathic pain remains largely unknown. Epigenetic mechanisms may play a major role in regulating expression of pro- or antinociceptive genes. DNA methylation is a major epigenetic mechanism in vertebrates, and methyl- CpG-binding protein 2 (MeCP2) is directly involved in methylation-mediated gene silencing. ⋯ Mechanical allodynia and thermal hyperalgesia induced by CCI were attenuated by intrathecal 5-azacytidine from day 5 to day 14 after CCI surgery. The increases in global DNA methylation and MeCP2 expression in the spinal cord in CCI rats were also significantly inhibited by intrathecal 5-azacytidine. These results demonstrate that increased global DNA methylation and MeCP2 expression in the spinal cord after nerve damage may play an important role in neuropathic pain. 5-azacytidine shows potential for treating neuropathic pain.
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Autism has been hypothesized to reflect neuronal disconnection. Several recent reports implicate the key thalamic relay nuclei and cortico-thalamic connectivity in the pathophysiology of autism. Accordingly, we aimed to focus on evaluating the integrity of the thalamic radiation and sought to replicate prior white matter findings in Korean boys with high-functioning autism spectrum disorders (ASD) using Diffusion Tensor Imaging (DTI). ⋯ Our preliminary findings support evidence implicating disturbances in the thalamo-frontal connections in autism. These findings highlight the role of hypoconnectivity between the frontal cortex and thalamus in ASD.