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  • 1
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Ionic channels appear to play an important role in contractile responses of the cerebral arteries and, thereby, contribute to the regulation of cerebral circulation. In the present study, we investigated the role of large-conductance Ca2+-activated K+ (BKCa) channels in the regulation of cerebral arterial tone during chronic hypertension.2. Ring segments of the basilar artery from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were placed in bath chambers and the isometric tension of each ring was measured.3. Application of inhibitors of BKCa channels, namely tetraethylammonium (TEA; ≥ 0.1 mmol/L) and charybdotoxin (CTX; ≥ 0.1 nmol/L), produced spontaneous contraction with rhythmic oscillation in the basilar artery from SHR.4. The oscillatory contraction was not induced by 5-hydroxytryptamine (0.01–10 μmol/L) or depolarization by external high K+ (20–60 mmol/L).5. The rhythmic contraction was completely abolished by either the removal of external Ca2+ or the application of nicardipine (10 nmol/L).6. The oscillation was not affected by the substitution of external Cl– by various equimolar anions (i.e. acetate, benezenesulphonate, bromide and isethianate).7. The amplitude of the oscillation was dose-dependently increased by the vasodilators forskolin and sodium nitroprusside, as well as by stimulation of the endothelium with histamine and acetylcholine, whereas the frequency was decreased.8. In contrast, the oscillation was eliminated by depletion of Ca2+ stores by caffeine. Neither TEA (10 mmol/L) nor CTX (10 nmol/L) produced any significant contraction of the basilar artery in WKY rats.9. These results suggest that BKCa channels may play an important role in regulating the resting tone of the cerebral artery in SHR.
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  • 2
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Cerebral infarction is the most common type of stroke and often causes long-term disability. To investigate the genetic contribution to cerebral infarction, we conducted a case-control study using 52,608 gene-based tag SNPs selected from the JSNP database. Here we report that a nonsynonymous SNP in ...
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  • 3
    ISSN: 1573-6903
    Keywords: Hypothermia ; cerebral ischemia ; cerebral blood flow ; brain tissue metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To investigate the effect of selective hypothermia of the brain (brain cooling) on regional cerebral blood flow and tissue metabolism, we have developed a brain thermo-regulator. Brain temperature was modulated by a water-cooled metallic plate placed on the surface of the rats' scalp to get the appropriate brain temperature precisely with ease. Regional cerebral blood flow and brain temperature were measured simultaneously using a Teflon-coated platinum electrode and thermocouple probe inserted stereotaxically into the parietal cortex and thalamus in spontaneously hypertensive rats. Experimental forebrain ischemia was induced by the occlusion of bilateral common carotid artery under normo- and hypothermic brain condition, and the supratentorial brain tissue metabolites were measured enzymatically after 60 min of forebrain ischemia. When cortical temperature was set to hypothermia, cortical blood flow was significantly lowered by 40% at 30°C and 20% at 33°C as compared with that at 36°C (p 〈 0.0001 and p 〈 0.05, respectively). Thalamic blood flow was also significantly reduced by 20% when cortical temperature was set to 30°C as compared with 36°C (p 〈 0.05). There were no significant differences in arterial blood pressure and gas parameters throughout these experiments. In the rats with selective brain hypothermia (30°C) immediately after the induction of cerebral ischemia, the level of brain ATP concentration after 60 min of ischemia was significantly higher than that in normothermia rats (36°C) (p 〈 0.05). Our findings indicate that: 1) the metallic plate brain thermo-regulator is useful in small animal experiments; 2) regional brain temperature regulates regional cerebral blood flow; and 3) selective brain hypothermia, even started after the forebrain ischemia, ameliorates the derangement of brain metabolism, suggesting its effectiveness as a cytoprotective strategy.
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  • 4
    ISSN: 1573-6903
    Keywords: Calcium antagonist ; isradipine ; spontaneously hypertensive rats (SHR) ; incomplete cerebral ischemia ; brain tissue metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study was designed to examine the effect of a calcium antagonist isradipine (PN200-110: PN) on local cerebral blood flow and brain tissue metabolism after 1-hour supratentorial ischemia induced by bilateral carotid artery ligation (BCL) in spontaneously hypertensive rats (SHR). PN, dissolved in ethanol plus polyethylene glycol 400, diluted with saline to make the final concentration of 0.25mg/ml and 2.5mg/ml, was administered subcutaneously either 30 min prior to BCL or just after the induction of incomplete cerebral ischemia (n = 7 in each group). Vehicle injection was served as a control group (n = 7). Cerebral blood flow in the parietal cortex (CBF) and the cerebellar cortex (CeBF) was measured by hydrogen clearance technique, and the supra- and infratentorial metabolites of the brain frozen in situ were determined by the enzymatic method. Blood pressure was lowered, but CBF was increased by PN administration in pre-BCL treatment study. After 1 hour of BCL, CBF decreased to around 10% or less of the resting value, being insignificant among the groups. Brain adenosine triphosphate was better preserved in PN-administered groups. The increase in lactate level tended to reduce dose dependently by PN treatment. PN also reduced the metabolic alterations in brain tissue with significance, even when administered just after the induction of forebrain ischemia. It is considered that pre- as well as post-BCL administration of PN is beneficial to attenuate the metabolic alterations in incomplete forebrain ischemia in SHR.
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