Neuroscience letters
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Neuroscience letters · Aug 2013
Alterations of mean diffusivity in brain white matter and deep gray matter in Parkinson's disease.
Although Parkinson's disease is a neurodegenerative disease primarily involving basal ganglia and midbrain, the deficit of white matter is also involved during the disease progression. As the diffusion tensor imaging method is sensitive to the microstructural changes, we investigated the microstructural alterations in white matter and deep gray matter in patients with Parkinson's disease. Brain images of 64 patients and sex- and age-matched 64 healthy controls were obtained from a 3T MRI scanner. ⋯ There were white matter deficits in the corticofugal tract, cingulum, uncinate fasciculus, crus of fornix or stria terminalis, corpus callosum, external capsule, superior longitudinal fasciculus, posterior thalamic radiation including optic radiation, and the tracts adjacent to the precuneus and supramarginal gyrus, as indicated by higher mean diffusivity in Parkinson's disease patients than in controls. There were also deficits in the left putamen, pallidum, thalamus, and caudate as indicated by higher mean diffusivity in Parkinson's disease patients than in controls. Using diffusion tensor imaging and multi-methods of image analysis, we successfully characterized and visualized brain white matter and deep gray matter areas with microstructural deficits in Parkinson's disease patients.
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Neuroscience letters · Aug 2013
The inhibition of cocaine-induced locomotor activity by CART 55-102 is lost after repeated cocaine administration.
CART peptide is known for having an inhibitory effect on cocaine- and dopamine-mediated actions after acute administration of cocaine and dopamine. In this regard, it is postulated to be a homeostatic, regulatory factor on dopaminergic activity in the nucleus accumbens (NAc). ⋯ The loss of CART peptide's inhibitory effect did not return for up to 9 weeks after stopping the repeated cocaine administration. It may not be surprising that homeostatic regulatory mechanisms in the NAc are lost after repeated cocaine administration, and that this may be a mechanism in the development of addiction.
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Neuroscience letters · Aug 2013
Involvement of the dorsal hippocampal dopamine D2 receptors in histamine-induced anxiogenic-like effects in mice.
Anxiety-related behaviors increase histamine and dopamine release in the brain. On the other hand, central histamine counteracts reward and reinforcement processes mediated by the mesolimbic dopamine system. We investigated the effects of the histaminergic system and dopamine D2 receptors agents and their interactions on anxiety-related behaviors using the elevated plus-maze (EPM). ⋯ Histamine can decrease dopaminergic tone in the dorsal hippocampus through decreasing the endogenous dopamine release, whereas quinpirole does the same via the postsynaptic DA receptors' activation. Sulpiride however renders the same effect through autoreceptors' blockade and potentiated dopamine transmission. Thus, quinpirole and sulpiride seem to compensate the effects of the intra-CA1 injection of exogenous histamine, and tend to exert anxiolytic effects in the presence of histamine.
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Neuroscience letters · Aug 2013
Randomized Controlled TrialThe dopamine agonist apomorphine enhances conditioned pain modulation in healthy humans.
Although cumulative evidence suggests that dopamine plays a role in pain processing, the mechanisms by which dopaminergic transmission affects pain remain elusive. Conditioned pain modulation (CPM) is a psychophysical paradigm based on endogenous descending inhibitory pain modulation. The current study was aimed to test the effects of apomorphine, a non-specific dopamine agonist, on the magnitude of CPM in healthy subjects. ⋯ RM-ANOVA revealed a significant interaction between 'session' and 'time' factors (F=5.316, p=0.023, η=0.054), and significant effect for the 'session' (F=5.719, p=0.019, η=0.006), but not for the 'time' (F=0.586, p=0.446, η=0.057). These results suggest that dopaminergic pathways both participate in and enhance pain modulation, represented by CPM. The role of dopamine in pain processing should be further studied.
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Neuroscience letters · Aug 2013
Facilitation of corticospinal tract excitability by transcranial direct current stimulation combined with voluntary grip exercise.
Previous studies have established that transcranial direct current stimulation (tDCS) is a powerful technique for the deliberate manipulation of the activity of human cerebral cortex. Moreover, it has also been shown that the non-exhausted voluntary motor exercise increases the excitability of corticospinal tract. ⋯ Our result showed that the combination of anodal tDCS with voluntary grip exercise produced a 2-fold increase in the amplitude of MEP as compared with single use of anodal tDCS or voluntary grip exercise. In conclusion, our result could indicate that the treatment outcomes of brain and neurorehabilitation using tDCS would be better when tDCS is combined with the appropriate method of voluntary exercise as compared with single use of tDCS.