Blood flow and capillary surface area of rat posterior canal ampulla

Vascular disorders have often been proposed to explain disorders of the inner ear, in both the cochlear and vestibular systems. While the cochlea has been extensively studied, little work has been done on vestibular blood flow. Existing studies have reported only total vestibular blood flow, using microspheres. By combining the physiologic technique of microsphere injection with new developments in morphologic stereology studies, data on end-organ blood flow (excluding nerve; 0.074 +/- 0.027 microliters/min; 5.99 microliters/min/mm3), capillary surface area (10.87 mm2/mm3), mean capillary diameter (9.64 microns), and end-organ volume (0.013 mm3) was determined for the posterior canal ampulla of young Fischer 344 rats. Results indicate an anatomic basis for increases in blood flow with CO2 breathing, and provide an assessment of appropriate microsphere size for vestibular blood flow studies. By allowing comparison of blood flow and capillary parameters related to surface area and volume, this new method of blood flow study will allow more meaningful data to be collected on the vestibular system.