Changes in cerebral microcirculation during and after abdominal aortic cross-clamping in rabbits: the role of thromboxane A2 receptor.
Little is known about any changes in cerebral hemodynamics, during and after abdominal aortic cross-clamping and unclamping, especially in the cerebral microcirculation. We studied the effects of abdominal aortic cross-clamping and unclamping on cerebral pial vessel diameter in the presence or absence of the thromboxane (Tx)A(2) receptor antagonist using a closed cranial window in 27 rabbits. Although infrarenal aortic cross-clamping did not affect pial vessel diameter, release of a 20-min aortic cross-clamp caused pial arterioles to dilate and then constrict. A significant constriction persisted for at least 60 min (maximum, -17% for large [> or =75 micro m] and -28% for small arterioles [<75 micro m] compared with baseline). Topical administration of a TxA(2) receptor antagonist, seratrodast, at 10(-7) M and 10(-6) M, significantly attenuated the constriction of large and small arterioles (at 60 min, -9% and -13% constriction for 10(-7) M, and -6% and -7% for 10(-6) M). Release of a 20-min aortic cross-clamp induced a sustained pial arteriolar constriction. Because this unclamping-induced vasoconstriction was attenuated by topical administration of seratrodast, it was likely partially mediated via the washout of TxA(2) produced in the ischemic region during the clamp and after cross-clamp release.


CONCLUSIONS
Abdominal aortic unclamping after a 20-min clamp caused an initial dilation followed by a sustained constriction of pial arterioles. Seratrodast, a thromboxane A(2) receptor antagonist, attenuated the vasoconstriction suggesting that it is at least partly mediated by thromboxane A(2) washed out from the region rendered ischemic by clamping.
Uchida
Masayoshi
M
Departments of *Anesthesiology and Critical Care Medicine and †Internal Medicine, Gifu University School of Medicine, Gifu City, Japan.
Iida
Hiroki
H
Iida
Mami
M
Dohi
Shuji
S
D000818:Animals; D001012:Aorta, Abdominal / Q000502:physiology*; D001160:Arterioles / Q000502:physiology; D016227:Benzoquinones / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003250:Constriction; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000502:physiology; D006538:Heptanoic Acids / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008833:Microcirculation / Q000502:physiology; D011448:Prostaglandin Antagonists / Q000494:pharmacology; D011817:Rabbits; D017482:Receptors, Thromboxane / Q000187:drug effects*; D013929:Thromboxane B2 / Q000097:blood
D016227:Benzoquinones; D006538:Heptanoic Acids; D011448:Prostaglandin Antagonists; D017482:Receptors, Thromboxane; D002245:Carbon Dioxide; C060230:seratrodast; D013929:Thromboxane B2