title: Platelet adhesion and arteriolar dilation in the photothrombosis: observation with the rat closed cranial and spinal windows.
abstract: The mechanism of cerebral infarction, in which thrombus formation and platelet-endothelium interaction play an important part, have not yet been clearly elucidated in vivo. The aim of this study was to observe rolling and adherent platelets and to analyze adherent leukocytes and vessel diameter change in vivo using a photothrombotic vessel occlusion model.A photothrombosis, which is mediated by free radicals, was induced in male Wistar rats in the presence of a photosensitizing dye (Photofrin II) and exposure to a filtered light. Rhodamine 6G-labeled platelets and leukocytes were visualized with intravital fluorescence videomicroscopy through a closed cranial or spinal window. The vessel diameter, photothrombosis and leukocyte adhesion were analyzed. Rolling and adherent platelets were observed during irradiation through the cerebral and spinal window. Before the platelets were recognized, the irradiated arteriole dilated significantly. After the photochemical occlusion of an arteriole, other arterioles also dilated and the adherent leukocytes increased in the venules. The photothrombosis were almost completely composed of platelets according to electron microscopic analysis. The arteriolar dilation rate and the number of adherent leukocytes in the cerebrum were greater than those in the spinal cord. By combining the photochemical thrombus formation and the fluorescence microscope techniques, we were able for the first time to observe rolling and adherent platelets and microvascular responses during photothrombosis in the cerebral and spinal microvasculature. It is suggested that free radicals, which can lead to platelet aggregation, play an important role as a cerebral vasodilator. This model is useful for cerebral and spinal microcirculatory analysis to investigate the platelet-endothelium interaction, the platelet aggregation and the effect of free radicals on cerebral and spinal microcirculation.
authors.affiliation: Clinical Research Unit, National Saitama Hospital, 2-1 Suwa, Saitama 351-0102, Wako-city, Japan. mishik@lsuhsc.edu
authors.forename: Mami
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Eiichi
authors.initials: E
authors.lastname: Sekizuka
authors.forename: Chikara
authors.initials: C
authors.lastname: Oshio
authors.forename: Shuzo
authors.initials: S
authors.lastname: Sato
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Yamaguchi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Terao
authors.forename: Kosuke
authors.initials: K
authors.lastname: Tsukada
authors.forename: Haruyuki
authors.initials: H
authors.lastname: Minamitani
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kawase
mesh_terms: D000818:Animals; D001160:Arterioles / Q000503:physiopathology*; D001792:Blood Platelets / Q000473:pathology / Q000648:ultrastructure; D002448:Cell Adhesion / Q000502:physiology; D015194:Diffusion Chambers, Culture; D017323:Dihematoporphyrin Ether; D004195:Disease Models, Animal; D018450:Disease Progression; D004730:Endothelium, Vascular / Q000648:ultrastructure; D020767:Intracranial Thrombosis / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology; D007962:Leukocytes / Q000502:physiology; D008028:Light Coagulation; D008297:Male; D008833:Microcirculation / Q000503:physiopathology; D010973:Platelet Adhesiveness; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000098:blood supply*; D013687:Telencephalon / Q000098:blood supply*; D013927:Thrombosis / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D014664:Vasodilation; D014699:Venules / Q000503:physiopathology
chemical_list: D017323:Dihematoporphyrin Ether