This research was supported by NIH/NIDCD R21 DC016157 (X.Shi), NIH/NIDCD R01 DC015781 (X.Shi), NIH/NIDCD R01-DC010844 (X.Shi),&#160;and Medical Research Foundation from Oregon Health and Science University (OHSU) (X.Shi).

NOTE: This is a non-survival surgery. All procedures involving the use of animals were reviewed and approved by the Institutional Animal Care and Use Committee at Oregon Health &#38; Science University (IACUC approval number: TR01_IP00000968).
1. Preparation of the fluorescent-labeled blood cells
<ol>
	<li>Anesthetize the donor mice (male C57BL/6J mice aged ~6 weeks) with an intraperitoneal (i.p.) injection of ketamine/xylazine anesthetic solution (5 mL/kg, see the Table of Materials...

<ol>
	<li>Shi, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiopathology+of+the+cochlear+microcirculation.">Physiopathology of the cochlear microcirculation.</a> Hearing Research. 282 (1), 10-24 (2011).</li><li>Brown, J. N., Miller, J. M., Nuttall, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Age-related+changes+in+cochlear+vascular+conductance+in+mice.">Age-related changes in cochlear vascular conductance in mice.</a> Hearing Research. 86 (1), 189-194 (1995).</li><li>Gratton, M. A., Schmiedt, R. A., Schulte, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Age-related+decreases+in+endocochlear+potential+are+associated+with+vascular+abnormalities+in+the+stria+vascularis+[corrected+and+republished+article+originallly+printed+in+Hearing+Research.">Age-related decreases in endocochlear potential are associated with vascular abnormalities in the stria vascularis [corrected and republished article originallly printed in Hearing Research.</a> Hearing Research. 94 (1-2), 181-190 (1996).</li><li>Le Prell, C. G., Yamashita, D., Minami, S. B., Yamasoba, T., Miller, J. 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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studies+of+inner+ear+blood+flow+in+animals+and+human+beings.">Studies of inner ear blood flow in animals and human beings.</a> Otolaryngology-Head and Neck Surgery. 112 (1), 101-113 (1995).</li><li>Nakashima, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disorders+of+cochlear+blood+flow.">Disorders of cochlear blood flow.</a> Brain Research Reviews. 43 (1), 17-28 (2003).</li><li>Nuttall, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sound-induced+cochlear+ischemia/hypoxia+as+a+mechanism+of+hearing+loss.">Sound-induced cochlear ischemia/hypoxia as a mechanism of hearing loss.</a> Noise and Health. 2 (5), 17 (1999).</li><li>Trune, D. R., Nguyen-Huynh, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascular+pathophysiology+in+hearing+disorders.">Vascular pathophysiology in hearing disorders.</a> Seminars in Hearing. , 242-250 (2012).</li><li>Nakashima, T., Hattori, T., Sone, M., Sato, E., Tominaga, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blood+flow+measurements+in+the+ears+of+patients+receiving+cochlear+implants.">Blood flow measurements in the ears of patients receiving cochlear implants.</a> The Annals of otology, rhinology, and laryngology. 111 (11), 998-1001 (2002).</li><li>Ren, T., Brechtelsbauer, P. B., Miller, J. M., Nuttall, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cochlear+blood+flow+measured+by+averaged+laser+Doppler+flowmetry+(ALDF).">Cochlear blood flow measured by averaged laser Doppler flowmetry (ALDF).</a> Hearing Research. 77 (1-2), 200-206 (1994).</li><li>Goodwin, P. C., Miller, J. M., Dengerink, H. A., Wright, J. W., Axelsson, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+laser+Doppler:+a+non-invasive+measure+of+cochlear+blood+flow.">The laser Doppler: a non-invasive measure of cochlear blood flow.</a> Acta Otolaryngologica. 98 (5-6), 403-412 (1984).</li><li>Le Floc'h, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Markers+of+cochlear+inflammation+using+MRI.">Markers of cochlear inflammation using MRI.</a> Journal of Magnetic Resonance Imaging. 39 (1), 150-161 (2014).</li><li>Axelsson, A., Nuttall, A. L., Miller, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Observations+of+cochlear+microcirculation+using+intravital+microscopy.">Observations of cochlear microcirculation using intravital microscopy.</a> Acta Otolaryngologica. 109 (3-4), 263-270 (1990).</li><li>Monfared, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+imaging+of+mammalian+cochlear+blood+flow+using+fluorescence+microendoscopy.">In vivo imaging of mammalian cochlear blood flow using fluorescence microendoscopy.</a> Otology &amp; Neurotology. 27 (2), 144 (2006).</li><li>Kong, T. H., Yu, S., Jung, B., Choi, J. S., Seo, Y. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+blood-flow+in+the+mouse+cochlea+using+an+endoscopic+laser+speckle+contrast+imaging+system.">Monitoring blood-flow in the mouse cochlea using an endoscopic laser speckle contrast imaging system.</a> PLoS One. 13 (2), 0191978 (2018).</li><li>Angelborg, C., Hillerdal, M., Hultcrantz, E., Larsen, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+microsphere+method+for+studies+of+inner+ear+blood+flow.">The microsphere method for studies of inner ear blood flow.</a> ORL. 50 (6), 355-362 (1988).</li><li>Choudhury, N., Chen, F., Shi, X., Nuttall, A. L., Wang, R. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Volumetric+imaging+of+blood+flow+within+cochlea+in+gerbil+in+vivo.">Volumetric imaging of blood flow within cochlea in gerbil in vivo.</a> IEEE Journal of Selected Topics in Quantum Electronics. 16 (3), 524-529 (2010).</li><li>Subhash, H. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Volumetric+in+vivo+imaging+of+microvascular+perfusion+within+the+intact+cochlea+in+mice+using+ultra-high+sensitive+optical+microangiography.">Volumetric in vivo imaging of microvascular perfusion within the intact cochlea in mice using ultra-high sensitive optical microangiography.</a> IEEE Transactions on Medical Imaging. 30 (2), 224-230 (2011).</li><li>Reif, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+hypoxia+induced+changes+in+cochlear+blood+flow+and+hemoglobin+concentration+using+a+combined+dual-wavelength+laser+speckle+contrast+imaging+and+Doppler+optical+microangiography+system.">Monitoring hypoxia induced changes in cochlear blood flow and hemoglobin concentration using a combined dual-wavelength laser speckle contrast imaging and Doppler optical microangiography system.</a> PLoS One. 7 (12), 52041 (2012).</li><li>Nuttall, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Techniques+for+the+observation+and+measurement+of+red+blood+cell+velocity+in+vessels+of+the+guinea+pig+cochlea.">Techniques for the observation and measurement of red blood cell velocity in vessels of the guinea pig cochlea.</a> Hearing Research. 27 (2), 111-119 (1987).</li><li>Nuttall, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cochlear+blood+flow:+measurement+techniques.">Cochlear blood flow: measurement techniques.</a> American Journal of Otolaryngology. 9 (6), 291-301 (1988).</li><li>Hanna, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automated+measurement+of+blood+flow+velocity+and+direction+and+hemoglobin+oxygen+saturation+in+the+rat+lung+using+intravital+microscopy.">Automated measurement of blood flow velocity and direction and hemoglobin oxygen saturation in the rat lung using intravital microscopy.</a> American Journal of Physiology. Lung Cellular Molecular Physiology. 304 (2), 86-91 (2013).</li><li>Narciso, M. G., Nasimuzzaman, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Purification+of+platelets+from+mouse+blood.">Purification of platelets from mouse blood.</a> Journal of Visualized Experiments. (147), e59803 (2019).</li><li>Shi, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thin+and+open+vessel+windows+for+intra-vital+fluorescence+imaging+of+murine+cochlear+blood+flow.">Thin and open vessel windows for intra-vital fluorescence imaging of murine cochlear blood flow.</a> Hearing Research. 313, 38-46 (2014).</li><li>Lorenz, J. 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Regulatory, Integrative, and Comparative Physiology. 282 (6), 1565-1582 (2002).</li><li>Dai, M., Shi, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fibro-vascular+coupling+in+the+control+of+cochlear+blood+flow.">Fibro-vascular coupling in the control of cochlear blood flow.</a> PloS One. 6 (6), 20652 (2011).</li><li>Shi, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cochlear+pericyte+responses+to+acoustic+trauma+and+the+involvement+of+hypoxia-inducible+factor-1alpha+and+vascular+endothelial+growth+factor.">Cochlear pericyte responses to acoustic trauma and the involvement of hypoxia-inducible factor-1alpha and vascular endothelial growth factor.</a> American Journal of Pathology. 174 (5), 1692-1704 (2009).</li><li>Hou, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Platelet-derived+growth+factor+subunit+B+signaling+promotes+pericyte+migration+in+response+to+loud+sound+in+the+cochlear+stria+vascularis.">Platelet-derived growth factor subunit B signaling promotes pericyte migration in response to loud sound in the cochlear stria vascularis.</a> Journal of the Association for Research in Otolaryngology. 19 (4), 363-379 (2018).</li><li>Hultcrantz, E., Nuttall, A. 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This paper demonstrates how capillaries in the cochlear lateral wall (and in the stria vascularis) of a mouse model can be visualized with fluorophore labeling in an open vessel-window preparation under a FIVM system. Mouse model is widely used and preferred as a mammalian model for investigating&#160; human health and disease. The protocol described here is a feasible approach for imaging and investigating CoBF in the mouse lateral wall (particularly in the stria vascularis) using an open vessel-window under FIVM system...

Normal function of the microcirculation in the lateral cochlear wall (comprising the majority of the capillaries in the spiral ligament and stria vascularis) is critically important for maintaining hearing function1. Abnormal CoBF is implicated in the pathophysiology of many inner ear disorders including noise-induced hearing loss, ear hydrops, and presbycusis2,3,4,5,6,7,8,9.&#160;Visualization of intravital CoBF will enable a better understanding of the links between hearing function and cochlear vascular pathology.
Although the complexity and location of the cochlea within the temporal bone precludes direct visualization and measurement of CoBF, various methods have been developed for the assessment of CoBF including laser-doppler flowmetry (LDF)10,11,12, magnetic resonance imaging (MRI)13, fluorescence intravital microscopy (FIVM)14, fluorescence microendoscopy (FME)15, endoscopic laser speckle contrast imaging (LSCI)16, and approaches based on the injection of labeled markers and radioactively tagged microspheres into the bloodstream (optical microangiography, OMAG)17,18,19,20. However, none of these methods has enabled absolute real-time tracking of changes in CoBF in vivo, with the exception of FIVM. FIVM, in combination with a vessel-window in the lateral cochlear wall, is an approach that has been used and validated in guinea pig under different experimental conditions by various laboratories14,21,22.
An FIVM method was successfully established for studying the structural and functional changes in the cochlear microcirculation in mouse using fluorescein isothiocyanate (FITC)-dextran as a contrast medium and a fluorescence dye-either DiO (3, 3&#8242;-dioctadecyloxacarbocyanine perchlorate, green) or Dil (1,1-dioctadecyl-3,3,3,3-tetramethylindocarbocyanine perchlorate, red)-for prelabeling blood cells, visualizing vessels, and tracking blood flow velocity. In the present study, the protocol of this method has been described for imaging and quantifying changes in CoBF in mouse under normal and pathological conditions (such as after noise exposure). This technique gives the researcher the tools needed to investigate the underlying mechanisms of CoBF related to hearing dysfunction and pathology in the stria vascularis, especially when applied in conjunction with readily available transgenic mouse models.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.9% Sodium Chloride</td>
			<td>Hospira</td>
			<td>NDC 0409-1966-02</td>
			<td>0.6 mL (for 1 mL)</td>
		</tr>
		<tr>
			<td>1,1&#8242;-Dioctadecyl-3,3,3&#8242;,3&#8242;-tetramethylindocarbocyanine perchlorate</td>
			<td>Sigma Aldrich</td>
			<td>468495</td>
			<td>20 &#181;M</td>
		</tr>
		<tr>
			<td>3,3&#8242;-Dioctadecyloxacarbocyanine perchlorateDio (3,3&#8242;-Dioctadecyloxacarbocyanine perchlorate</td>
			<td>Sigma Aldrich</td>
			<td>D4292</td>
			<td>20 &#181;M</td>
		</tr>
		<tr>
			<td>CODA Monitor system</td>
			<td>Kent scientific</td>
			<td></td>
			<td>CODA Monitor, for monitoring blood pressure and heartbeat</td>
		</tr>
		<tr>
			<td>Coverslip</td>
			<td>Fisher Scientific</td>
			<td>12-542A</td>
			<td></td>
		</tr>
		<tr>
			<td>DC Temperature Controller</td>
			<td>FHC</td>
			<td>40-90-8D</td>
			<td></td>
		</tr>
		<tr>
			<td>Fiji/ImageJ</td>
			<td>NIH</td>
			<td></td>
			<td>Measurement of vessel diameter</td>
		</tr>
		<tr>
			<td>FITC-dextran (2000 kDa)</td>
			<td>Sigma Aldrich</td>
			<td>FD2000s</td>
			<td>40 mg/mL</td>
		</tr>
		<tr>
			<td>Heparin Sodium Injection, USP MDV</td>
			<td>Mylan</td>
			<td>NDC 67457-374-12</td>
			<td>5000 USP units/mL</td>
		</tr>
		<tr>
			<td>Katathesia (100 mg/mL)</td>
			<td>Henry Schein</td>
			<td>NDC 11695-0702-1</td>
			<td>0.2 mL (for 1 mL)</td>
		</tr>
		<tr>
			<td>Microscope Objective</td>
			<td>Mitutoyo</td>
			<td>378-823-5</td>
			<td>Model: M Plan Apo NIR 10x</td>
		</tr>
		<tr>
			<td>ORCA-ER Camera</td>
			<td>Hamamatsu</td>
			<td></td>
			<td>Model: C4742-80-12AG</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Gibco</td>
			<td>2085387</td>
			<td></td>
		</tr>
		<tr>
			<td>Xyzaine (100 mg/ml, 5x diluted for use )</td>
			<td>Lloyd</td>
			<td>LPFL04821</td>
			<td>0.2 mL (for 1 mL)</td>
		</tr>
		<tr>
			<td>Zoom Stereo Microscope</td>
			<td>Olympus</td>
			<td></td>
			<td>Model: SZ61, fluorescent microscope</td>
		</tr>
	</tbody>
</table>

measurement of strial blood flow in mouse cochlea utilizing an open vessel-window and intravital fluorescence microscopy

Transduction of sound is metabolically demanding, and the normal function of the microvasculature in the lateral wall is critical for maintaining endocochlear potential, ion transport, and fluid balance. Different forms of hearing disorders are reported to involve abnormal microcirculation in the cochlea. Investigation of how cochlear blood flow (CoBF) pathology affects hearing function is challenging due to the lack of feasible interrogation methods and the difficulty in accessing the inner ear. An open vessel-window in the lateral cochlear wall, combined with fluorescence intravital microscopy, has been used for studying CoBF changes in vivo, but mostly in guinea pig and only recently in the mouse. This paper and the associated video describe the open vessel-window method for visualizing blood flow in the mouse cochlea. Details include 1) preparation of the fluorescent-labeled blood cell suspension from mice; 2) construction of an open vessel-window for intravital microscopy in an anesthetized mouse, and 3) measurement of blood flow velocity and volume using an offline recording of the imaging. The method is presented in video format to show how to use the open window approach in mouse to investigate structural and functional changes in the cochlear microcirculation under normal and pathological conditions.

After surgical exposure of the cochlear capillaries in the lateral wall (Figure 1), intravital high-resolution fluorescence microscopic observation of Dil-labeled blood cells in FITC-dextran-labeled vessels was feasible through an open vessel-window. Figure 2A is a representative image taken under FIVM that shows the capillaries of the mouse cochlear apex-middle turn lateral wall. The lumina of these vessels is made visible by th...

Watch this Scientific Journal Video about Measurement of Strial Blood Flow in Mouse Cochlea Utilizing an Open Vessel-Window and Intravital Fluorescence Microscopy at JoVE.com

Measurement of Strial Blood Flow in Mouse Cochlea Utilizing an Open Vessel-Window and Intravital Fluorescence Microscopy

An open vessel-window approach using fluorescent tracers provides sufficient resolution for cochlear blood flow (CoBF) measurement. The method facilitates the study of structural and functional changes in CoBF in mouse under normal and pathological conditions.

Transduction of sound is metabolically demanding, and the normal function of the microvasculature in the lateral wall is critical for maintaining ...

Normal blood supply to cochlea is critically important for cochlea Meniere's Disease especially for maintaining indoor cochlear potential which is the essential driving force for hair cells transaction. This function of blood circulation has been closely associated with different forms of hearing loss. Better understanding of cochlear blood flow will enable more effective management of hearing disorders resulting from blood flow dysfunction.However, direct blood flow measurement is very very challenging due to difficulty to assess the inner ear. Techniques for assessing cochlear blood flow is currently still under development. Here we demonstrate one of the recent methods established in our lab open muscle window in accommodation with high resolution fluorescence microscope to narrow cochlear blood flow in small animal species such as mouse.Application of this technique with transgenetic mass models has the potential for advancing research to unravel the links between hearing function and the pathology related to cochlear blood flow in intravascular risk. Our procedures should be conducted with caution. In addition to momentary body hemorrhage, animal's vital signs, including blood pressure and heartbeat, must be monitored during your surgery.Begin by collecting approximately one millimeter of blood in heparin by cardiac puncture. Centrifuge the blood at 3000 times G for three minutes at four degrees Celsius. Remove the plasma, then wash the blood cell pellet with one milliliter of PBS three times by centrifugation at 3000 times G for three minutes at four degrees Celsius.Label the blood cells with one milliliter of 20 micromolar DiO or Dil in PBS, and incubate in the dark for 30 minutes at room temperature. Wash the labeled blood cells with one milliliter of PBS and centrifuge three times at 3000 times G for three minutes. Resuspend the cell pellet in 30%hematocrit with approximately 0.9 milliliters of PBS before injection.Prepare sterile surgical instruments and imaging platform and place a heating pad beneath the drape. Monitor the poor reflex and general muscle tone of the anesthetized mice to check the depth of the anesthesia. Place the animal on the warm heating pad and its tail in the monitor system for monitoring blood pressure and heartbeat.Maintain the rectal temperature at 37 degrees Celsius and record the animal's systolic blood pressure, diastolic blood pressure, and mean blood pressure in the anesthetized condition. Open the left tympanic bulla via a lateral and vental approach under a stereo microscope leaving the tympanic membrane and ossicles intact. Make an incision along the midline of the animal's neck with its head immobilized to minimize movement.Remove the left sub mandibular gland and posterior belly of the digastric muscle and cauterize. Locate and expose the bony bulla by identifying the sternocleidomastoid muscle and facial nerve extending anterior toward the bulla. Open the bony bulla with a 30 gauge needle and carefully remove the surrounding bone with surgical tweezers to provide a clear view of the cochlear and stapedial artery with its medial margin lying over the edge of the round window niche and causing anterior superior towards the oval window.Use a small knife blade to scrape the lateral wall bone at the apex middle turn of the mouse cochlea approximately 1.25 millimeters from the apex until a thin spot is cracked. Remove the bone chips with small wire hooks. Cover the vessel window with a cut cover slip to preserve normal physiological conditions and provide an optical view for recording vessel images.Make a one centimeter incision along the right saphenous vein to expose the vessel. Successively infuse 100 microliters each of the FITC-Dextran solution and the blood cell suspension into the animal through the saphenous vein to enable visualization of the blood vessels and tracking of blood flow. Observe the blood flow in real time on a video monitor five minutes after the injection.Image the blood vessels using a fluorescence microscope equipped with a long working distance objective and a lamp housing containing a multiple band excitation filter and compatible emission filter. Record the video using a high resolution digital black and white charge coupled device camera acquiring more than 350 images per video. To ensure successful analysis of the flow velocity.Measure the vessel diameter using appropriate software and determine the distance between two fixed points across the vessel in the acquired images. Open the video of blood flow in the software and set the scale of the images. Track the selected DiO stained blood cells using the tracking function.Then use the distance the cells have moved and the interval of time between image frames in the video for auto calculation of the flow velocity. Calculate the volumetric flow using the equation given in the text manuscript. To create the noise exposure model before blood flow recording, place the animals in wire mesh cages and expose them to broadband noise at 120 decibels sound pressure level in a sound exposure booth for three hours.Then for an additional three hours on the next day. Record blood flow two weeks after noise exposure. After surgical exposure of the cochlear capillaries in the lateral wall, intravital high resolution fluorescence microscopic observation of DiL labeled blood cells in FITC Dextran labeled vessels was performed through an open vessel window.DiL labeled blood cells in Stria vessels labeled with FITC Dextran are shown here. Dio labeled blood cells labeled with FITC Dextran show that the vessel density of the spiral ligament is sparser than that of the denser Stria vascularis. High resolution IVM shows the blood flow patterns in control and noise exposed groups.The disturbed pattern of blood circulation can be seen in the noise exposed groups. Anomalies included reduced vessel diameter and increased variation in vessel diameter. The blood flow velocities in the control and noise exposed groups were calculated by tracking the roots of the DiO labeled blood cells.The blood velocity and volume in the noise exposed group were significantly lower than in the control group. The successful establishment of the open vessel window requires a high degree of surgical skill. Care must be exercised in removing the bone of the cochlear lateral wall.

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JoVE Journal

Medicine

2.2K Views.  Oregon Health & Science University. Normal blood supply to cochlea is critically important for cochlea Meniere's Disease especially for maintaining indoor cochlear potential which is the essential driving force for hair cells transaction. This function of blood circulation has been closely associated with different forms of hearing loss. Better understanding of cochlear blood flow will enable more effective management of hearing disorders resulting from blood flow dysfunction.However, direct blood flow measurement is ver...