Cochlear Blood Flow

Miller, Josef M.; Nuttall, Alfred L.

doi:10.1007/978-1-4757-2083-9_18

Cited by 18 publications

(5 citation statements)

References 65 publications

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“…We also determine the relationship between the alterations of CBF and EP during capsaicin perfusion, inasmuch as the EP depends on the CBF. The CBF was measured using the laser Doppler flowmetry (LDF) technique (Miller and Nuttall 1990). Briefly, the cochlear mucosa was gently removed with a cotton pledget.…”

Section: Extracochlear Current Stimulation and Eeoae Measurement-mentioning

confidence: 99%

Vanilloid Receptors in Hearing: Altered Cochlear Sensitivity by Vanilloids and Expression of TRPV1 in the Organ of Corti

Zheng¹,

Dai²,

Steyger³

et al. 2003

Journal of Neurophysiology

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Capsaicin, the vanilloid that selectively activates vanilloid receptors (VRs) on sensory neurons for noxious perception, has been reported to increase cochlear blood flow (CBF). VR-related receptors have also been found in the inner ear. This study aims to address the question as to whether VRs exist in the organ of Corti and play a role in cochlear physiology. Capsaicin or the more potent VR agonist, resiniferatoxin (RTX), was infused into the scala tympani of guinea pig cochlea, and their effects on cochlear sensitivity were investigated. Capsaicin (20 microM) elevated the threshold of auditory nerve compound action potential and reduced the magnitude of cochlear microphonic and electrically evoked otoacoustic emissions. These effects were reversible and could be blocked by a competitive antagonist, capsazepine. Application of 2 microM RTX resulted in cochlear sensitivity alterations similar to that by capsaicin, which could also be blocked by capsazepine. A desensitization phenomenon was observed in the case of prolonged perfusion with either capsaicin or RTX. Brief increase of CBF by capsaicin was confirmed, and the endocochlear potential was not decreased. Basilar membrane velocity (BM) growth functions near the best frequency and BM tuning were altered by capsaicin. Immunohistochemistry study revealed the presence of vanilloid receptor type 1 of the transient receptor potential channel family in the hair cells and supporting cells of the organ of Corti and the spiral ganglion cells of the cochlea. The results indicate that the main action of capsaicin is on outer hair cells and suggest that VRs in the cochlea play a role in cochlear homeostasis.

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Section: Extracochlear Current Stimulation and Eeoae Measurement-mentioning

confidence: 99%

Vanilloid Receptors in Hearing: Altered Cochlear Sensitivity by Vanilloids and Expression of TRPV1 in the Organ of Corti

Zheng¹,

Dai²,

Steyger³

et al. 2003

Journal of Neurophysiology

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“…For laser Doppler flowmetry, TSI (TSI, Minnesota, USA) and Perimed PF3 (Perimed, Sweden) laser flowmeters were used as described in detail by Miller and Nuttall [6]. The tympanic bullae were exposed surgically using a ventral approach, the mucosa over the second turn of the cochlea was gently removed and petroleum jelly was applied between the laser probe and the bone in order to improve optical coupling.…”

Section: Animals and Preparationmentioning

confidence: 99%

The vascular mechanism of action of betahistine in the inner ear of the guinea pig

Laurikainen

Miller

Nuttall

et al. 1998

European Archives of Oto-Rhino-Laryngology

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The aim of this study was to investigate the mechanism and site of action of betahistine dihydrochloride in the inner ear of the guinea pig. Betahistine-evoked increases in cochlear blood flow (CBF) have been presumed to be due to the drug effect on the later wall capillary bed or larger feeding vessels in the cochlea vascular system. As such, the mechanism of action could be due to inhibition of H3 receptors. Betahistine may also have a direct effect on postsynaptic H1/H2 receptors and/or an effect modulated by other autonomic receptors. Betahistine-evoked CBF responses were assessed by laser Doppler flowmetry in the presence of an H3 agonist (alpha N-methyl-histamine dihydrochloride), an H3 antagonist (thioperamide), an H2 antagonist (cimetidine) or an alpha 2 antagonist (idazoxan). The effects of betahistine on circulation in the anterior inferior cerebellar artery (AICA) and ipsilateral stria vascularis (SV) were assessed using intravital microscopy (IVM). Findings showed that betahistine increased CBF and reduced systemic blood pressure (BP). In contrast, alpha N-methylhistamine dihydrochloride had no effect on baseline CBF or BP and did not influence betahistine-induced increases in CBF. Thioperamide reversed the effects of betahistine on CBF, but had no effect on baseline CBF or BP. Cimetidine had no marked effect on baseline CBF or betahistine-induced increases in CBF Idazoxan had no consistent effects on baseline CBF, but abolished the effect of betahistine on CBF. The mean increase of red blood cell velocity in SV capillaries was 15% and occurred without a demonstrable change in capillary diameters. In contrast, the diameter of the AICA increased by 17-20%, indicating that betahistine-evoked increases in CBF resulted primarily from vasodilatation of the AICA. We suggest that this effect may be mediated via presynaptic H3 heteroreceptors and autonomic alpha 2 receptors.

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“…The technique has many attractive features including (1) ease of operation, (2) continuous measurement, and (3) noninterference with btood flow in the microcircutation, since the technique involves illuminating the tissue with monochromatic light. These attributes of LDF have led several research groups to utilize the tech-nique in the assessment of tissue perfusion in various vascular beds, including skin (Johnson,19X4), the gas-troint~stina~ system (Shepherd and Redel, 19821, skeletal muscle (Tyml et al, 1990), kidney (Roman and Smits, 1985), brain (Haberl et al, 19891, bone (Hellem et al, 1983), nose CDruce et al, 1984), eye (Riva et al, 19901, and cochlea (Miller and Nuttall, 1990).…”

Section: Introductionmentioning

confidence: 99%

Cochlear blood flow measured by averaged laser Doppler flowmetry (ALDF)

et al. 1994

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This report describes a new approach to estimate the hydromechanical properties of a vascular system. Averaged laser Doppler flowmetry (ALDF) was developed by averaging the flux signal of a laser Doppler flowmeter (LDF) synchronized to the heart cycle. The usefulness of this method was verified by manipulation of the cochlear microvasculature. Twelve pigmented guinea pigs under pentobarbital/fentanyl anesthesia were used. The cochlea was surgically exposed and the LDF probe placed on the bony surface of the first turn to monitor cochlear blood flow (CBF). The LDF flux signal (0.2 s time constant) was sampled by an A/D board at 2 kHz for 255 ms and averaged with synchronization to the heart beat. The mean blood flow, peak to peak amplitude, and time (phase) delay of pulsatile flow were measured from the averaged signal. According to a transmission line model of the vascular system, under a given perfusion pressure, mean flow reflects resistance while amplitude and time delay of the pulsatile flow are related to the reactance component of the impedance of the vascular system. During the formation of photochemically-induced thrombosis in the cochlear microvasculature, there was a dramatic mean flux decrease (90.1 +/- 3.4% from baseline (BL), N = 6). Additionally, a time-dependent decrease in amplitude and time delay of pulsatile flow were indicated by ALDF. These results suggest a large increase in vascular resistance and significant decrease in compliance.(ABSTRACT TRUNCATED AT 250 WORDS)

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Cochlear Blood Flow

Cited by 18 publications

References 65 publications

Vanilloid Receptors in Hearing: Altered Cochlear Sensitivity by Vanilloids and Expression of TRPV1 in the Organ of Corti

Vanilloid Receptors in Hearing: Altered Cochlear Sensitivity by Vanilloids and Expression of TRPV1 in the Organ of Corti

The vascular mechanism of action of betahistine in the inner ear of the guinea pig

Cochlear blood flow measured by averaged laser Doppler flowmetry (ALDF)

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