Quantitative analysis of rat inner ear blood flow using the iodo[(14)C]antipyrine technique

A number of different qualitative and quantitative techniques have been used to measure inner ear blood flow and all have required that the animal be anesthetized. It is well known that anesthesia can cause a variety of circulatory as well as other systemic changes. In this study, we have employed a technique commonly used for quantifying brain blood flow, the iodo[(14)C]antipyrine technique ([(14)C]IAP). Unlike other techniques, [(14)C]IAP can be used in unanesthetized animals under conditions that are nearly normal, it is non-invasive, it can be used reliably in regions of low local blood flow, and data can be acquired from both the periphery and central nervous system. Results show that blood flow to the lateral wall of the basal turn of the cochlea (387 +/- 19 microl/g/min) is significantly higher (P<0.001) than that of the utricular macula (189 +/- 23 microl/g/min), horizontal (186 +/- 22 microl/g/min), superior (185 +/- 22 microl/g/min), or posterior canal crista (185 +/- 25 microl/g/min). Surprisingly, blood flow to all of the vestibular end-organs is remarkably similar. The use of this technique should allow pharmacological experimentation on inner ear blood flow without the unknown complications of anesthesia or invasive procedures.