Microcirculatory Responses To Repeated Embolism-Reperfusion In Cerebral Microvessels Of Cat: A Fluorescence Videomicroscopic Study

Intra-carotid injections of degradable starch microspheres (DSMs) can induce DSM embolism-reperfusion in the level of cerebral arterioles. Vascular responses of cerebral arterioles to repeated DSM embolism (ischemia)-reperfusion were examined when DSMs were injected twice through a carotid artery with a time interval of 30 min. Arteriolar diameter was measured from images of arterioles filled with rhodamine-B isothiocyanate dextran and red cell velocity was measured with a dual window technique using FITC-labeled red cells as a flow tracer. DSM embolization induced ischemia (flow reduction including stasis) for approximately 10 min in the level of microvessels (arterioles). Cerebral arterioles began to dilate immediately after embolism induced by the DSM injection and vasodilation was sustained until reperfusion. After reperfusion the arteriole began to constrict and the arteriolar diameter returned to the initial diameter level at approximately 20 min after the DSM injection. The arteriolar diameters for the second DSM embolism showed a similar response to those for the first embolism in 7 out of 8 cats. It can be concluded that the vascular response of cerebral arterioles to the second embolism-reperfusion could not be affected by the first embolism-reperfusion.