Browsing by keyword "Postpartum Depression: Action Towards Causes and Treatment (PACT) Consortium"
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Spreading waves of a reduced diffusion coefficient of water in normal and ischemic rat brainUsing echo planar diffusion-weighted magnetic resonance imaging, we measured three-dimensional changes in the apparent diffusion coefficient (ADC) of water in eight contiguous coronal slices, encompassing the entire rat brain, before and after local cortical stimulation. We applied chemical (potassium chloride application; n = 6) and mechanical (needle stab; n = 4) stimulations to the right posterior parietal rat cortex. In all animals in which potassium chloride or the needle stab was applied, a region of decreased ADC values to a mean of 0.45 +/- 0.03 x 10(-5)cm2/s occurred. These reduced ADC levels appeared in the posterior parietal cortex within 1 min after cortical stimulation and the change recovered within 1 min. Then a ripple-like movement of similar changes developed across the unilateral cortex. This change was localized to the cortex and no significant ADC changes occurred in subcortical structures. The propagating speed of this movement was 3.4 +/- 0.5 mm/min. These findings are compatible with spreading depression as observed electrophysiologically. Similar ADC changes occurred in areas distinct from the ischemic lesion in 3 of 12 animals subjected to focal cerebral ischemia. This magnetic resonance method could detect spreading ADC decline if it occurred in human diseases including brain ischemia.
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Spreading waves of decreased diffusion coefficient after cortical stimulation in the rat brainA method is demonstrated for the noninvasive detection and study of spreading cortical depression. Spreading depression (SD) was elicited in rats by topical application of potassium chloride to the exposed cortex. The apparent diffusion coefficient (Dapp) of water in a region of the cortex, measured using a PFG-NMR spin echo sequence with an observation time of 40 ms, declines 35% within 30 s and recovers to the normal value within the next 30 s. The region of decreased Dapp was shown to be 2 mm in size and to move in the cortex, away from the point of application, with a uniform velocity of 3.3 +/- 0.5 mm/min. The behavior of the affected region is consistent with other reports of the behavior of SD as monitored by electrophysiological means. The technique can be implemented on currently available MRI equipment and makes possible the noninvasive study of SD in animal models of neurological disorders, their therapeutic intervention, and possibly the study of SD in humans.
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Visualization of cortical spreading depression using manganese-enhanced magnetic resonance imagingCortical spreading depression (CSD) was visualized using manganese-enhanced MRI (MEMRI) following topical application of KCl to the exposed rat cortex. MEMRI signal increase in the ipsilateral cortex relative to the contralateral control region was 60 +/- 30% following two KCl applications. MEMRI signal increase for a single (40%) versus double (80%) KCl application suggests an integration effect over successive CSD episodes. CSD-induced MEMRI enhancement involved cortical layers containing dense regions of apical dendrites, supporting the contention that these neuronal structures are necessary for propagation of CSDs. Subcortical enhancement was present in hippocampal and thalamic regions, most likely a result of neuronal connections with cortical layers 4 and 5. These results are consistent with previous studies of CSD using diffusion-weighted MRI and T(2) (*)-weighted MRI and should be useful for investigating CSD itself and its role in other neurologic disorders.