ABSTRACT
The effect of 60 minutes of exposure to high-frequency (10- to 40-kHz), high-intensity (115-dB) noise on the cochlear blood flow (CoBF) was investigated in adult gerbils. The CoBF was measured with a newly improved microsphere method. The number of microspheres in cochlear tissue that had been dissected by the surface preparation technique was assessed by direct counting. Our experiments have indicated that the CoBF is elevated even after 60 minutes of noise exposure. This was true particularly in the areas where these frequencies stimulate the cochlea. The noise also increased CoBF in the opposite ear in areas not corresponding to the stimulation frequencies (second and third turn). This phenomenon is under further investigation.
Subject(s)
Cochlea/blood supply , Microcirculation , Noise , Animals , Dogs , Environmental Exposure , Gerbillinae , Microspheres , Regional Blood FlowABSTRACT
A newly-developed procedure which combines the microsphere method with surface preparation dissection was employed in an investigation of blood flow in cochleas of anesthetized gerbils. In these experiments, 10.1 +/- 0.9 microns carbon-coated microspheres were injected into the left auricle of the heart and a reference blood sample withdrawn at 0.165 ml/min from the iliac artery. The blood flow in the lateral portion (stria vascularis, ligamentum spirale, and suprastria) was calculated to be 337.20, 184.00 and 24.75 nl/min; in the spiral portion (basilar membrane, lamina spiralis ossea, and limbus spiralis) it was found to be 85.40, 39.55 and 6.10 nl/min; and in the central portion (modiolus) it was found to be 256.55, 43.60 and 2.45 nl/min in the first, second and third turns, respectively. The total blood flow in the left and right membranous cochleas was 1062.70 and 896.60 nl/min, respectively. Averaged total blood flow in both ears was 979.60 nl/min. This is a first attempt to measure blood flow in the very small, functionally different areas of the cochlea. This work has shown that it is possible to measure and compare blood flow between the turns and between different functional parts within the turns.
