Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism
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J. Cereb. Blood Flow Metab. · Feb 2000
Effects of variations in interstimulus interval on activation-flow coupling response and somatosensory evoked potentials with forepaw stimulation in the rat.
In functional neuroimaging studies, the hemodynamic response to functional activation is used as a surrogate marker for neuronal activity, typically in response to task paradigms that use periodic stimuli. With use of a model system of electrical forepaw stimulation in rats (n = 14) with laser-Doppler (LD) monitoring of cerebral blood flow (CBF) changes in the somatosensory cortex, the effects of variations in the interstimulus interval (ISI) on the hemodynamic response to periodic stimuli were examined. A characteristic peak flow response was seen for 4-second stimuli and a peak and plateau response were seen for all 8-second stimuli regardless of ISI. ⋯ Somatosensory evoked potential responses were also recorded in some rats (n = 8) and remained unchanged for the various ISIs for a particular stimulus duration. These results suggest that the decrease in the LD(CBF) responses observed with shorter ISIs likely represents a refractoriness of the hemodynamic response and not neuronal function. These results may have important implications for the optimization and interpretation of functional activation paradigms that use periodic stimuli.
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J. Cereb. Blood Flow Metab. · Feb 2000
Induction of angiopoietin and Tie receptor mRNA expression after cerebral ischemia-reperfusion.
The angiopoietin/Tie receptor system may contribute to angiogenesis and vascular remodeling by mediating interactions of endothelial cells with smooth muscle cells and pericytes. The temporal expression of angiopoietin-1 (Angpo-1), angiopoietin-2 (Angpo-2), Tie-1, and Tie-2 mRNA was studied in a focal cerebral ischemia model in rats. The cDNA fragments obtained from reverse transcription polymerase chain reaction amplification were cloned and used as a probe to detect individual genes. ⋯ The temporal profiles of the expression of these genes were different from those of other angiogenic genes such as basic fibrobast growth factor/fibroblast growth factor receptor and vascular endothelial growth factor/vascular endothelial growth factor receptor and proteolytic enzymes (tissue-type plasminogen activator and urokinase plasminogen activator) and their inhibitors (plasminogen activator inhibitor-1). The expression patterns of these genes could be related to progressive tissue liquefaction and neovascularization after ischemia in this stroke model. Differential expression of these angiogenesis genes suggests the involvement of complex regulatory mechanisms that remain to be characterized.
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J. Cereb. Blood Flow Metab. · Jan 2000
Effect of JTP-2942, a novel thyrotropin-releasing hormone analog, on motor deficits after chronic focal cerebral ischemia in rats.
To investigate the chronic effects of a novel thyrotropin-releasing hormone analog, JTP-2942 (N(alpha)-[(1S, 2R)-2-methyl-4-oxocyclopentylcarbonyl]-L-histidyl-L-prolinamide monohydrate), on behavioral changes after stroke, the authors examined its effects on motor and neurologic deficits using a middle cerebral artery (MCA) occlusion model in rats. A left MCA was permanently occluded at a proximal site. From 1 week after occlusion, JTP-2942 was intravenously administered once a day for 4 weeks. ⋯ In the present study, long-lasting improving effects of JTP-2942 on the impairment of motor and neurologic functions were observed in rats with MCA occlusion, which continued after cessation of drug administration and which were not attributable to a reduction in ipsilateral cerebral shrinkage. It is considered that the effect of JTP-2942 on functional recovery is attributable to the activation of substitutive functions such as neuronal reconstruction. These pharmacologic properties of JTP-2942 may be of interest for the treatment of patients with motor and neurologic deficits during the chronic or subacute phase of stroke.
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J. Cereb. Blood Flow Metab. · Oct 1999
Spectral analysis of arterial blood pressure and cerebral blood flow velocity during supine rest and orthostasis.
This study evaluates the effect of orthostasis on the low frequency (LF, 0.04 to 0.15 Hz) fluctuations in the blood flow velocity of the middle cerebral artery (MCAFV) in relation to its arterial blood pressure (ABP) equivalent to further define and quantify this relationship in cerebrovascular regulation. Spectral analysis was performed on 22 healthy subjects during supine rest and head-up tilt. The power in the LF range can be used to quantify the LF fluctuations, and four types of LF power data could be obtained for each individual: LF power of supine MCAFV, LF power of supine ABP, LF power of tilt MCAFV, and LF power of tilt ABP. ⋯ The authors found that this index was dependent on the extent of orthostatic MCAFV changes, and the dependency could be mathematically expressed (r = 0.61, P = .0001), suggesting its involvement in cerebrovascular regulation. Moreover, these data further support the previous observation that the LF fluctuations of MCAFV might result from modulation of its ABP equivalent, and the modulation effect could be quantified as the power ratio (LF power of MCAFV/ LF power of ABP). These observations could be an important step toward further insight into cerebrovascular regulation, which warrants more research in the future.
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J. Cereb. Blood Flow Metab. · Sep 1999
Cerebral vasodilatation causing acute intracranial hypertension: a method for noninvasive assessment.
Deep spontaneous vasodilatatory events are frequently recorded in various cerebral diseases, causing dramatic increases (A-waves) in intracranial pressure (ICP) and subsequently provoking ischemic brain insults. The relationship between fluctuations in CBF, ICP, and arterial blood pressure (ABP) is influenced by properties of cerebrovascular control mechanisms and the cerebrospinal pressure-volume compensation. The goal of this study was to construct a mathematical model of this relationship and to assess its ability to predict the occurrence and time course of A-waves. ⋯ The correlation coefficient between real and simulated increase in ICP was R = 0.98; P < .001. Similarly, correlation between real and simulated increase in pulse amplitude of ICP was highly significant (R = 0.94; P < .001). The mathematical model of the relationship between ABP, flow velocity, and ICP is of potential clinical use for the noninvasive detection of A-waves in patients in whom invasive ICP assessment is not conducted.