Local blood flow is determined by perfusion pressure in the tissue, radius of the blood capillary and blood viscosity. Cochlear blood flow changes during and after the infusion of following various drugs were recorded by the use of a laser Doppler flowmeter. In the experiments to change perfusion pressure, we observed the effects of Epinephrine, Angiotensin II, Trimetaphan camsylate (depressor) and several osmotic diuretics. Since 76% Urografin is a solution of a higher osmolarity in the contrast media for vasography and known to produce vasodilation in the legs when infused in the abdominal aorta. The effect of Urografin was compared with that of glycerol in regard to the effect on cochlear blood flow and systemic blood pressure. For the experiment on the effects of vasoactive agents, we measured the changes of cochlear blood flow during and after the infusion of Prostaglandin E1, Prostaglandin E2, and Dihydroergotamin. To evaluate the influence of viscosity factor on cochlear blood flow, we used Batroxobin for defibrinogenation, Erythropoetin to produce polycythemic condition, normal saline for hemodilution and Pentoxyfilline to facilitate erythrocyte deformability. Pentoxyfilline was found to exert the increasing effect in cochlear blood flow, especially in the animal with a higher hematocrit value. These findings may imply the significance for understanding the physiology of cochlear blood flow as well as pharmacoclogy of above mentioned agents in the cochlear microcirculation.
