Brain research bulletin
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Brain research bulletin · Dec 2006
Functional changes in the activity of cerebellum and frontostriatal regions during externally and internally timed movement in Parkinson's disease.
We used fMRI to investigate the neurofunctional basis of externally and internally timed movements in Parkinson's disease (PD) patients. Ten PD patients whose medication had been withheld for at least 18h and 11 age- and sex-matched healthy controls were scanned while performing continuation paradigm with a visual metronome. Compared with the controls, PD patients displayed an intact capability to store and reproduce movement frequencies but with a significantly increased movement latencies. ⋯ By contrast, in the continuation phase the only neural network involved to a greater extent by the PD group was the cerebello-thalamic pathway. The lack of neurofunctional differences between the two timing phases suggests that rhythmic externally and internally guided movements engage similar neural networks in PD and matched healthy controls. Moreover, between-group comparison indicates that PD patients OFF medication may compensate for their basal ganglia-cortical loop's dysfunction using different motor pathways involving cerebellum and basal ganglia relays during the two phases of rhythmic movement.
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Brain research bulletin · Dec 2006
Methylenetetrahydrofolate reductase gene polymorphisms are associated with ischemic and hemorrhagic stroke: Dual effect of MTHFR polymorphisms C677T and A1298C.
Hyperhomocysteinemia is an independent risk factor for ischemic stroke. The enzyme methylenetetrahydrofolate reductase (MTHFR) plays a critical role in modulating the levels of plasma homocysteine. Two polymorphisms in the MTHFR gene, C677T, A1298C result in reduced enzyme activity. ⋯ The MTHFR 1298C allele (chi(2)=11.166; P=0.004), C1298C genotype (OR=2.950; P=0.001), and C677C/C1298C compound genotype (OR=3.463, P=0.0001) were strongly associated with ischemic stroke. Interestingly however, the MTHFR 677T allele (chi(2)=6.033; P=0.049), T677T genotype (OR=3.120; P=0.014), and T677T/A1298A compound genotype (OR=4.211; P=0.002) were associated with hemorrhagic stroke. In conclusion, the C677T and A1298C polymorphisms of the MTHFR gene are genetic risk factors for hamorrhagic and ischemic stroke respectively, independent of other atherothrombotic risk factors.
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Brain research bulletin · Dec 2006
Stimulation of mu and delta opioid receptors induces hyperalgesia while stimulation of kappa receptors induces antinociception in the hot plate test in the naked mole-rat (Heterocephalus glaber).
The antinociceptive effects of highly selective mu (DAMGO), delta (DPDPE) and kappa (U-50488 and U-69593) opioid agonists were evaluated following intraperitoneal (i.p.) administration in the naked mole-rat. A hot plate test set at 60 degrees C was used as a nociceptive test and the latency to the stamping of the right hind paw (response latency) was used as the end-point. DAMGO (5-10 mg/kg) and DPDPE (2.5-5 mg/kg) caused a naloxone-reversible significant decrease in the mean response latency. ⋯ These results showed that activation of mu or delta receptors caused hyperalgesia, whereas activation of kappa receptors caused antinociception in the hot plate test in naked mole-rat. This suggests that mu and delta receptors modulate thermal pain in a different way than kappa receptors in the naked mole-rat. It is not possible at the moment to point out how they modulate thermal pain as little is known about the neuropharmacology of the naked mole-rat.