Invited Symposium: Stroke/Cerebral Vasospasm
Lessov, N (Department of Neurology, Oregon Health Sciences University, USA)
Clark, WM (Department of Neurology, Oregon Health Sciences University, USA)
We have previously demonstrated that the myogenic activity of middle cerebral arteries (MCAs) that were ischemic for 2 hours and reperfused for 2 minutes was similar to that of nonischemic control arteries (Stroke 1997 28:176-80). In the present study, we investigated the combined effect of ischemia and tPA exposure on diameter regulation of MCAs. The intraluminal suture model of focal cerebral ischemia was used to induce 2 hours of ischemia, after which occluded MCAs were removed and studed in vitro using an arteriograph system that allowed control of transmural pressure and measurement of lumen diameter. Arteries were either nonischemic (control, n=8) or ischemic and perfused with 400micrograms/mL tPA (tPA, n=6). After a 1 hour equilibration at 75mmHg, pressure was increased to 125mmHg and diameter recorded. Control arteries developed 22±3% tone during equilibration at 75mmHg and responded myogenically when pressure was increased to 125mmHg, decreasing diameter from 232±8 microns to 229±6 microns (n.s.) and increasing the level of tone to 26±2% (n.s. vs. 75mmHg). The tPA arteries developed a similar level of tone as control arteries (24±4%, n.s.). However, increasing pressure to 125mmHg caused an increase in diameter from 228±5 to 270±10 microns, decreasing the level of tone to 12±3% (p < 0.01 vs. 75mmHg). The slope of the pressure vs. diameter curve for control arteries was negative (-0.06±-0.01), but was positive for the tPA arteries (0.86±0.27), demonstrating a loss of diameter regulation and myogenic reactivity in the tPA arteries. These results demonstrate that the combination of ischemia and tPA perfusion alters cerebrovascular function. The loss of myogenic reactivity in these arteries may have profound effects on cerebrovascular resistance and autoregulation of cerebral blood flow during or after reperfusion.
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|Cipolla, MJ; Lessov, N; Clark, WM; (1998). Middle Cerebral Artery Function After Ischemia, Reperfusion and Thrombolytic Therapy. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/zhang/cipolla0451/index.html|
|© 1998 Author(s) Hold Copyright|