Noise-induced changes in red blood cell velocity in lateral wall vessels of the rat cochlea

The effects of loud sound on the microvasculature of the cochlea are not well characterized or understood. Morphological changes in the stria vascularis and changes in blood flow are known to occur during or following sound stimulation, however, the effects on cochlear blood flow appear to be complex. Studies have shown that noise exposure may produce increases in blood flow, decreases in blood flow, or no measureable change in blood flow. These inconsistent results probably reflect the various noise exposure parameters, the animal model used, and could be a function of the specific procedures utilized to assess blood flow changes. The purpose of the current study was to investigate the effects of one specific class of sound exposure (high intensity noise) on red blood cell velocity in the capillaries of the second turn of the rat cochlea using intravital microscopy. This class of sound exposure was selected in order to attempt a confirmation of previous findings of increased blood flow (Perlman and Kimura, 1962) using the quantitative technique of red blood cell velocity measurement. Following determination of pre-exposure red blood cell velocities in capillaries of the rat cochlea second turn, animals were exposed to 133 dB or 110 dB broad-band noise for ten minutes. The red blood cell velocity was recorded continuously during the exposure. Exposure to both sound intensities disrupted stable and orderly baseline flow patterns and resulted in overall intensity-dependent increases in red blood cell velocity.(ABSTRACT TRUNCATED AT 250 WORDS)