BLOOD-FLOW AND ASSESSMENT OF CAPILLARIES IN THE AGING RAT POSTERIOR CANAL CRISTA

Vascular change has been proposed as an etiological factor in inner ear aging and in several inner ear disorders. Moreover, some successful medical management of the episodic vertigo and tinnitus associated with Meniere's disease has been directed toward pharmacologically increasing blood flow, changing vascular permeability or ion homeostasis. While there are many studies of cochlear capillary morphology and blood flow, there are very few examining these variables in the vestibular system and none with respect to aging. The purpose of this study was to examine the rat posterior canal ampullary crista for age-related changes in blood flow and capillary morphology. By combining stereological techniques with microsphere injection, we have determined that in the rat posterior canal crista there is a statistically significant age-related decrease in blood flow (75%), mean capillary diameter (31%), and volume fraction of capillary lumen (31%). There is also an overall 18% decrease in the volume of the ampullary crista, a 72% decrease in blood flow/unit volume and a 36% increase in capillary length/unit volume. There were no significant changes in the capillary surface area/unit volume, the absolute capillary length, or the absolute capillary surface area. These data suggest impaired blood flow and degenerative loss of the ampullary crista may be relate to impaired end organ function.