CHANGES IN THE ENDOCOCHLEAR POTENTIAL AND COCHLEAR BLOOD-FLOW INDUCEDBY ATP INFUSION AND ARTERIAL-OCCLUSION

To assess the relationship between cochlear blood flow (CBF) and audit ory function, a procedure of intravital microscopy for observations of the lateral wall vessels of the cochlea coupled with the simultaneous measurement of the endocochlear potential (EP) was established in gui nea pigs with gradual ischemia of the cochlea. It was found that occlu sions of both common carotid arteries and one of the vertebral arterie s produced a minor reduction in CBP with no significant alteration in the EP. When intravenous infusion of ATP induced sharp and severe decr eases in CBF, the EP varied only slightly from the baseline in some an imals while there were no alteration in others. Furthermore, ATP infus ions combined with arterial occlusions caused even more severe decline s in CBF and a moderate decrease in the EP. The results indicate that not only does the CBF satisfy the basic needs of the processes of coch lear function, but also has a regulatory mechanism to ensure the norma l function of the cochlea in the ischemia condition. It was also found that the changes in the shia vascularis vessels induced by decreases in blood pressure (BP) and heart rates were more severe than those of the spiral ligament vessels. This phenomenon indicated that the stria vascularis vessels were more sensitive to decreases of BP and heart ra tes.