250 Scientific Programme 22. European Stroke Conference © 2013 S. Karger AG, Basel 8 Experimental studies Tissue plasminogen activator reduces infarction size in mouse thromboembolic model despite failure to recanalize the middle cerebral artery. S. Ansar1, E. Handwerker2, R. Thiagarajah3, L. Tritschler4, M. Fatar5, M. Hennerici6, S. Meairs7 Department of Experimental Neurology, Mannheim University Hospital, University of Hei-delberg,, Mannheim, GERMANY1, Department of Experimental Neurology, Mannheim Univer-sity Hospital, University of Heidelberg,, Mannheim, GERMANY2, Department of Experimental Neurology, Mannheim University Hospital, University of Heidelberg,, Mannheim, GERMANY3, Department of Experimental Neurology, Mannheim University Hospital, University of Heidelberg,, Mannheim, GERMANY4, Department of Neurology, Mannheim University Hospital, University of Heidelberg,, Mannheim, GERMANY5, Department of Neurology, Mannheim University Hospital, University of Heidelberg,, Mannheim, GERMANY6, Department of Neurology, Mannheim Univer-sity Hospital, University of Heidelberg,, Mannheim, GERMANY7 Background: A recent study suggests that patients with persistent occlusion of the middle cerebral artery (MCA) following treatment with recombinant tissue plasminogen activator (rt-PA) have better outcomes than patients not receiving t-PA. We performed a study to elucidate possible mechanisms of this finding in a new model of thromboembolic stroke closely mimicking human pathophysiolo-gy. Methods: Thromboembolic stroke was induced by local injection of thrombin directly into the right MCA of C57 black/6J mice. Rt-PA was administered 20 and 40 min after clot formation. The efficiency of rt-PA to induce thrombolysis was measured by laser Doppler. After 24 h, all animals were euthanized and interleukin (IL)-6, tumor necrosis factor-alpha (TNF-α), matrix metallopro-teinase (MMP)-9, Caspase-3, hsp 32 and hsp 70 protein levels were investigated by immunofluo-rescence. Presence of hemorrhage was verified and infarct volume was measured using histology. Results: Early rt-PA treatment starting at 20 min after clot formation resulted in 100% recanaliza-tion. However, rt-PA-induced thrombolysis only dissolved the clot in 38 % of the animals when administered at 40 min. IL-6, TNF-α, MMP-9, Caspase-3, hsp 32 and hsp 70 were increased after MCAO whereas treatment with rt-PA attenuated the expressions of inflammatory markers in animals where thrombolysis was successful. Infarct size was significantly reduced with rt-PA treatment com-pared to non-treated MCAO, regardless of whether MCA thrombolysis was successful. There was no significant difference in hemorrhage between non- and early treated animals (p < 0.01). However, rt-PA treatment at 40 min showed signs of hemorrhage in 42%. Conclusion: Our study demonstrates a clear correlation of the protein expression of inflammatory mediators, apoptosis and stress genes with the recanalization data after rt-PA treatment. In this model rt-PA treatment decreases the infarct size regardless of whether vessel recanalization is successful. 7 Experimental studies Endogenous and exogenous alteration of spreading depolarization in the post-stroke brain A.Y. Jin1, D.A. Petrin2, R.D. Andrew3, N. Peterson4 Queen’s University, Kingston, CANADA1, Queen’s University, Kingston, CANADA2, Queen’s University, Kingston, CANADA3, Queen’s University, Kingston, CANADA4 Background: Spreading depolarization (SD) after acute stroke leads to infarct expansion, but the mechanisms of SD in the post-stroke brain remain unclear. We examined the ability of post-isch-emic cortex to support SD under conditions which alter depolarizing events. Methods: Following focal cerebral ischemia in male C57BL/6J mice (n=32), 350μm live brain slic-es (n=164) were incubated in artificial CSF at 34C for up to 4 hours. Using changes in tissue light transmittance (LT) in the ipsi- and contralateral hemispheres following oxygen glucose deprivation (OGD), we observed alterations in SD onset latency and wavefront velocity upon exposure to 30 μM carbetapentane (CP), 10 μM dibucaine (DB), 1μM dipropylcyclopentylxanthine (DPCPX) and 1 μM ouabain. Ouabain 100 μM was also used in place of OGD to examine the differential effect of recurrent ischemia vs Na/K-ATPase blockade on SD. Results: In the post-stroke hemisphere, OGD-induced SD was delayed by 33% (n=29, p< 0.001) and SD wavefront velocity was decreased by 42% (n=5, p = 0.016). The adenosine A1 antagonist DPCPX marginally accelerated SD onset in the post-stroke hemisphere (n=3, p=0.0546) whereas CP (n=9) and DB (n=9) both delayed SD onset by 28% (p=0.01) and 30% (p=0.001) respectively. Blockade of all isoforms of Na/K-ATPase with 100 μM ouabain in place of OGD abrogated differ-ences in SD onset and wavefront velocity between the post-stroke and non-stroke hemispheres; pref-erential blockade of the alpha2/3 isoforms with ouabain at 1 μM did not. Conclusions: Following acute stroke, peri-infarct tissue has a decreased susceptibility to spreading depolarization. Adenosine A1 receptor activity may modulate post-stroke SD. Blockade of the al-pha1 but not alpha2/3 isoforms of Na/K-ATPase promotes SD in the post-stroke brain. CP and DB increase resistance to SD in peri-infarct tissue and may attenuate the damage caused by recurrent ischemic depolarization.
Karger_ESC London_2013
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