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

Vascular change has been proposed as an etiological factor in inner ea r aging and in several inner ear disorders. Moreover, some successful medical management of the episodic vertigo and tinnitus associated wit h Meniere's disease has been directed toward pharmacologically increas ing blood flow, changing vascular permeability or ion homeostasis. Whi le there are many studies of cochlear capillary morphology and blood f low, there are very few examining these variables in the vestibular sy stem and none with respect to aging. The purpose of this study was to examine the rat posterior canal ampullary crista for age-related chang es 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-re lated 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 bl ood flow/unit volume and a 36% increase in capillary length/unit volum e. There were no significant changes in the capillary surface area/uni t volume, the absolute capillary length, or the absolute capillary sur face area. These data suggest impaired blood flow and degenerative los s of the ampullary crista may be relate to impaired end organ function .