This investigation is concerned with the mechanisms that control blood flow in the cochlea, the degree or magnitude of such control, and the physical locations and effectors of the control. The nature of the blood-perilymph and blood-endolymph barriers are of additional interest as is the influence of the sympathetic nervous system on the cochlear blood supply. In-vivo blood flow velocity and blood vessel diameters are to be measured using light microscopic techniques. Analog and digital techniques will allow quantification of flow and vessel diameter changes for altered systemic blood pressure, cervical sympathetic ganglion electric stimulation, CO2 and O2 exposure, osmotic agents, and intense sound. Extensive use will be made of fluorescence microscopy using flurescein-isothiocyanate-labeled dextran and fluroescently labeled red blood cells. The dyes will be excited by xenon light epl-illumination or transillumination and recorded by an image intensified video camera and recording system. Quantitative analysis of cochlear vasculature will be accomplished by digital image processing techniques. Laser Doppler flowmetery will be used to determine cochlear blood flux changes and studies will be carried out to enlarge the understanding of the performance of this instrumentation. Expanded knowledge of laser-Doppler flowmetry will help bring this instrumentation closer to the possible future clinical application for the measurment of inner ear perfusion. Laser- Doppler flowmetry will be examined in experiments deriving comparative analytical measures of functional changes in cochlear blood flow which are assessed by hydrogen clearance (to measure regional blood flow), by oxygen sensitive microelectrodes (to measure intracochlear pO2), and from compound action potential responses (to test inner ear function). Autoregulation in the inner ear will be investigated by physically controlling systemic blood pressure with the aid of an extracorporeal blood recirculation system. The ultimate goal of the research is to determine the factors that influence cochlear microcirculation and the effect that circulation changes have on the inner ear. The studies will help us to understand normal homeostasis of the inner ear and clarify the role that microcirculation has in sudden deafness, fluctuant hearing, sound-induced hearing loss, and Meinere's disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS011731-14
Application #
3394576
Study Section
Hearing Research Study Section (HAR)
Project Start
1977-05-01
Project End
1992-06-30
Budget Start
1988-07-01
Budget End
1989-06-30
Support Year
14
Fiscal Year
1988
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Type
Schools of Medicine
DUNS #
791277940
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Axelsson, A; Nuttall, A L; Miller, J M (1990) Observations of cochlear microcirculation using intravital microscopy. Acta Otolaryngol 109:263-70
LaRouere, M J; Sillman, J S; Nuttall, A L et al. (1989) A comparison of laser Doppler and intravital microscopic measures of cochlear blood flow. Otolaryngol Head Neck Surg 101:375-84
Brown, J N; Thorne, P R; Nuttall, A L (1989) Blood pressure and other physiological responses in awake and anesthetized guinea pigs. Lab Anim Sci 39:142-8
Miller, J M; Dengerink, H (1988) Control of inner ear blood flow. Am J Otolaryngol 9:302-16
Nuttall, A L; Hultcrantz, E; Larsen, H C et al. (1988) Cochlear blood flow increases after systemic hemodilution: comparison of simultaneous laser Doppler flowmetry and radioactive microsphere measurements. Hear Res 34:215-23
Sillman, J S; LaRouere, M J; Nuttall, A L et al. (1988) Recent advances in cochlear blood flow measurements. Ann Otol Rhinol Laryngol 97:1-8
Miles, F P; Nuttall, A L (1988) In vivo capillary diameters in the stria vascularis and spiral ligament of the guinea pig cochlea. Hear Res 33:191-200
Nuttall, A L (1988) Cochlear blood flow: measurement techniques. Am J Otolaryngol 9:291-301
Hultcrantz, E (1988) Clinical treatment of vascular inner ear diseases. Am J Otolaryngol 9:317-22
Nuttall, A L (1987) Velocity of red blood cell flow in capillaries of the guinea pig cochlea. Hear Res 27:121-8

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