title: Luminal platelet aggregates in functional deficits in parenchymal vessels after subarachnoid hemorrhage.
abstract: The pathophysiology of early ischemic injury after aneurysmal subarachnoid hemorrhage (SAH) is not understood. This study examined the acute effect of endovascular puncture-induced SAH on parenchymal vessel function in rat, using intravascular fluorescent tracers to assess flow and vascular permeability and immunostaining to assess structural integrity and to visualize platelet aggregates. In sham-operated animals, vessels were well filled with tracer administered 10s before sacrifice, and parenchymal escape of tracer was rare. At ten minutes and three hours after hemorrhage, patches of poor vascular filling were distributed throughout the forebrain. Close examination of these regions revealed short segments of narrowed diameter along many profiles. Most vascular profiles with reduced perfusion contained platelet aggregates and in addition showed focal loss of collagen IV, a principal component of basal lamina. In contrast, vessels were well filled at 24h post-hemorrhage, indicating that vascular perfusion had recovered. Parenchymal escape of intravascular tracer was detected at 10 min post-hemorrhage and later as plumes of fluorescence emanating into parenchyma from restricted microvascular foci. These data demonstrate that parenchymal microvessels are compromised in function by 10 min after SAH and identify focal microvascular constriction and local accumulation of luminal platelet aggregates as potential initiators of that compromise.
authors.affiliation: Department of Neuroscience, Mount Sinai School of Medicine, New York, NY 10029, USA. fatima.sehba@mssm.edu
authors.forename: Victor
authors.initials: V
authors.lastname: Friedrich
authors.forename: Rowena
authors.initials: R
authors.lastname: Flores
authors.forename: Artur
authors.initials: A
authors.lastname: Muller
authors.forename: Fatima A
authors.initials: FA
authors.lastname: Sehba
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D001808:Blood Vessels / Q000378:metabolism / Q000503:physiopathology*; D001921:Brain / Q000098:blood supply / Q000378:metabolism / Q000503:physiopathology*; D002199:Capillary Permeability / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D024141:Collagen Type IV / Q000378:metabolism; D007150:Immunohistochemistry; D010974:Platelet Aggregation / Q000502:physiology*; D010976:Platelet Count; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013345:Subarachnoid Hemorrhage / Q000503:physiopathology*
chemical_list: D024141:Collagen Type IV