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Kong L, Domarecka E, Szczepek AJ. Histamine and Its Receptors in the Mammalian Inner Ear: A Scoping Review. Brain Sci 2023; 13:1101. [PMID: 37509031 PMCID: PMC10376984 DOI: 10.3390/brainsci13071101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 07/14/2023] [Accepted: 07/19/2023] [Indexed: 07/30/2023] Open
Abstract
BACKGROUND Histamine is a widely distributed biogenic amine with multiple biological functions mediated by specific receptors that determine the local effects of histamine. This review aims to summarize the published findings on the expression and functional roles of histamine receptors in the inner ear and to identify potential research hotspots and gaps. METHODS A search of the electronic databases PubMed, Web of Science, and OVID EMBASE was performed using the keywords histamine, cochlea*, and inner ear. Of the 181 studies identified, 18 eligible publications were included in the full-text analysis. RESULTS All four types of histamine receptors were identified in the mammalian inner ear. The functional studies of histamine in the inner ear were mainly in vitro. Clinical evidence suggests that histamine and its receptors may play a role in Ménière's disease, but the exact mechanism is not fully understood. The effects of histamine on hearing development remain unclear. CONCLUSIONS Existing studies have successfully determined the expression of all four histamine receptors in the mammalian inner ear. However, further functional studies are needed to explore the potential of histamine receptors as targets for the treatment of hearing and balance disorders.
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Affiliation(s)
- Lingyi Kong
- Department of Otorhinolaryngology, Head and Neck Surgery, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, 10117 Berlin, Germany
| | - Ewa Domarecka
- Department of Otorhinolaryngology, Head and Neck Surgery, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, 10117 Berlin, Germany
| | - Agnieszka J Szczepek
- Department of Otorhinolaryngology, Head and Neck Surgery, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, 10117 Berlin, Germany
- Faculty of Medicine and Health Sciences, University of Zielona Gora, 65-046 Zielona Gora, Poland
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Ernst BP, Heinrich UR, Fries M, Meuser R, Rader T, Eckrich J, Stauber RH, Strieth S. Cochlear implantation impairs intracochlear microcirculation and counteracts iNOS induction in guinea pigs. Front Cell Neurosci 2023; 17:1189980. [PMID: 37448696 PMCID: PMC10336219 DOI: 10.3389/fncel.2023.1189980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 06/06/2023] [Indexed: 07/15/2023] Open
Abstract
Introduction Preservation of residual hearing remains a great challenge during cochlear implantation. Cochlear implant (CI) electrode array insertion induces changes in the microvasculature as well as nitric oxide (NO)-dependent vessel dysfunction which have been identified as possible mediators of residual hearing loss after cochlear implantation. Methods A total of 24 guinea pigs were randomized to receive either a CI (n = 12) or a sham procedure (sham) by performing a cochleostomy without electrode array insertion (n = 12). The hearing threshold was determined using frequency-specific compound action potentials. To gain visual access to the stria vascularis, a microscopic window was created in the osseous cochlear lateral wall. Cochlear blood flow (CBF) and cochlear microvascular permeability (CMP) were evaluated immediately after treatment, as well as after 1 and 2 h, respectively. Finally, cochleae were resected for subsequent immunohistochemical analysis of the iNOS expression. Results The sham control group showed no change in mean CBF after 1 h (104.2 ± 0.7%) and 2 h (100.8 ± 3.6%) compared to baseline. In contrast, cochlear implantation resulted in a significant continuous decrease in CBF after 1 h (78.8 ± 8.1%, p < 0.001) and 2 h (60.6 ± 11.3%, p < 0.001). Additionally, the CI group exhibited a significantly increased CMP (+44.9% compared to baseline, p < 0.0001) and a significant increase in median hearing threshold (20.4 vs. 2.5 dB SPL, p = 0.0009) compared to sham after 2 h. Intriguingly, the CI group showed significantly lower iNOS-expression levels in the organ of Corti (329.5 vs. 54.33 AU, p = 0.0003), stria vascularis (596.7 vs. 48.51 AU, p < 0.0001), interdental cells (564.0 vs. 109.1 AU, p = 0.0003) and limbus fibrocytes (119.4 vs. 18.69 AU, p = 0.0286). Conclusion Mechanical and NO-dependent microvascular dysfunction seem to play a pivotal role in residual hearing loss after CI electrode array insertion. This may be facilitated by the implantation associated decrease in iNOS expression. Therefore, stabilization of cochlear microcirculation could be a therapeutic strategy to preserve residual hearing.
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Affiliation(s)
| | - Ulf-Rüdiger Heinrich
- Department of Otorhinolaryngology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Mathias Fries
- Department of Otorhinolaryngology, University Medical Center Bonn (UKB), Bonn, Germany
| | - Regina Meuser
- Institute for Medical Biometry, Epidemiology and Informatics (IMBEI), University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Tobias Rader
- Division of Audiology, Department of Otorhinolaryngology, University Hospital, Ludwig-Maximilians-Universität München (LMU), Munich, Germany
| | - Jonas Eckrich
- Department of Otorhinolaryngology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Roland H. Stauber
- Department of Otorhinolaryngology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Sebastian Strieth
- Department of Otorhinolaryngology, University Medical Center Bonn (UKB), Bonn, Germany
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Kloos B, Bertlich M, Spiegel JL, Freytag S, Lauer SK, Canis M, Weiss BG, Ihler F. Low Dose Betahistine in Combination With Selegiline Increases Cochlear Blood Flow in Guinea Pigs. Ann Otol Rhinol Laryngol 2022; 132:519-526. [PMID: 35656811 PMCID: PMC10108341 DOI: 10.1177/00034894221098803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Betahistine is frequently used in the pharmacotherapy for Menière's Disease (MD). Little is known about its mode of action and prescribed dosages vary. While betahistine had an increasing effect on cochlear microcirculation in earlier studies, low dose betahistine of 0.01 mg/kg bw or less was not able to effect this. Selegiline inhibits monoaminooxidase B and therefore potentially the breakdown of betahistine. The goal of this study was to examine whether the addition of selegiline to low dose betahistine leads to increased cochlear blood flow. METHODS Twelve Dunkin-Hartley guinea pigs were anesthetized, the cochlea was exposed and a window opened to the stria vascularis. Blood plasma was visualized by injecting fluoresceinisothiocyanate-dextrane and vessel diameter and erythrocyte velocity were evaluated over 20 minutes. One group received low dose betahistine (0.01 mg/kg bw) and selegiline (1 mg/kg bw) i.v. while the other group received only selegiline (1 mg/kg bw) and saline (0.9% NaCl) as placebo i.v. RESULTS Cochlear microcirculation increased significantly (P < .001) in guinea pigs treated with low dose betahistine combined with selegiline by up to 58.3 ± 38.7% above baseline over a period of up to 11 minutes. In one guinea pig, the increase was 104.6%. Treatment with Selegiline alone did not affect microcirculation significantly. CONCLUSIONS Low dose betahistine increased cochlear microcirculation significantly when combined with selegiline. This should be investigated in further studies regarding dose-effect relation in comparison to betahistine alone. Side effects, in particular regarding circulation, should be considered carefully in view of the clinical applicability of a combination therapy in patients with MD.
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Affiliation(s)
- Benedikt Kloos
- Department of Otorhinolaryngology, University Hospital, LMU Munich, Munich, Germany.,Institute of Surgical Research, Walter-Brendel-Centre of Experimental Medicine, University Hospital, LMU Munich, Munich, Germany.,German Center for Vertigo and Dizziness (DSGZ), LMU Munich, Munich, Germany
| | - Mattis Bertlich
- Department of Otorhinolaryngology, University Hospital, LMU Munich, Munich, Germany.,Department of Dermatology and Allergy, University Hospital, LMU Munich, Munich, Germany
| | - Jennifer L Spiegel
- Department of Otorhinolaryngology, University Hospital, LMU Munich, Munich, Germany
| | - Saskia Freytag
- Molecular Medicine, Harry Perkins Institute of Medical Research, Perth, WA, Australia
| | - Susanne K Lauer
- Clinic for Small Animal Surgery and Reproduction, LMU Munich, Munich, Germany
| | - Martin Canis
- Department of Otorhinolaryngology, University Hospital, LMU Munich, Munich, Germany
| | - Bernhard G Weiss
- Department of Otorhinolaryngology, University Hospital, LMU Munich, Munich, Germany
| | - Friedrich Ihler
- Department of Otorhinolaryngology, University Hospital, LMU Munich, Munich, Germany.,Institute of Surgical Research, Walter-Brendel-Centre of Experimental Medicine, University Hospital, LMU Munich, Munich, Germany.,German Center for Vertigo and Dizziness (DSGZ), LMU Munich, Munich, Germany.,Department of Ear, Nose and Throat Diseases, Head and Neck Surgery, Greifswald, Germany
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Weiss BG, Freytag S, Kloos B, Haubner F, Sharaf K, Spiegel JL, Canis M, Ihler F, Bertlich M. Cannabinoid Receptor 2 Agonism is Capable of Preventing Lipopolysaccharide Induced Decreases of Cochlear Microcirculation - A Potential Approach for Inner Ear Pathologies. Otol Neurotol 2021; 42:e1396-e1401. [PMID: 34267099 DOI: 10.1097/mao.0000000000003280] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
HYPOTHESIS The ability of JWH-133, an agonist at the cannabinoid receptor 2, to abrogate the effects of lipopolysaccharide on cochlear microcirculation was investigated. BACKGROUND Cochlear inflammation and subsequent impairment of microcirculation is part of numerous pathologies affecting inner ear function, including suppurative labyrinthitis, noise trauma, and sudden sensorineural hearing loss. One way of causing cochlear inflammation is exposing the cochlea to lipopolysaccharide, a bacterial endotoxin. METHODS Twenty Dunkin-hartley guinea pigs were divided into four groups of five animals each. Two groups received topic treatment with JWH-133 and two received treatment with placebo. One group that had been treated with JWH-133 and one with placebo were then exposed to lipopolysaccharide or placebo, respectively. Cochlear microcirculation was quantified before, in between and after treatments by in vivo fluorescence microscopy. RESULTS Significantly different changes in cochlear blood flow were only seen in the group that was treated with placebo and subsequently lipopolysaccharide. Every other group showed no significant change in cochlear blood flow. CONCLUSION JWH-133 is capable of abrogating the effects of lipopolysaccharide on cochlear microcirculation. It may therefore be clinical interest in treating numerous inflammation associated cochlear pathologies.
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Affiliation(s)
- Bernhard G Weiss
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Marchioninistr. 15
- Walter Brendel Centre of Experimental Medicine, University of Munich Hospital, Marchioninistr. 27, 81377 Munich, Germany
| | - Saskia Freytag
- Population Health and Immunity Division, Walter and Eliza Hall Institute, 1G Royal Parade
- Department of Medical Biology, University of Melbourne, 3052, Parkville, Australia
| | - Benedikt Kloos
- Walter Brendel Centre of Experimental Medicine, University of Munich Hospital, Marchioninistr. 27, 81377 Munich, Germany
| | - Frank Haubner
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Marchioninistr. 15
| | - Kariem Sharaf
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Marchioninistr. 15
- Walter Brendel Centre of Experimental Medicine, University of Munich Hospital, Marchioninistr. 27, 81377 Munich, Germany
| | - Jennifer Lee Spiegel
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Marchioninistr. 15
| | - Martin Canis
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Marchioninistr. 15
- Walter Brendel Centre of Experimental Medicine, University of Munich Hospital, Marchioninistr. 27, 81377 Munich, Germany
| | - Friedrich Ihler
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Marchioninistr. 15
- Walter Brendel Centre of Experimental Medicine, University of Munich Hospital, Marchioninistr. 27, 81377 Munich, Germany
| | - Mattis Bertlich
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Marchioninistr. 15
- Walter Brendel Centre of Experimental Medicine, University of Munich Hospital, Marchioninistr. 27, 81377 Munich, Germany
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Ihler F, Freytag S, Kloos B, Spiegel JL, Haubner F, Canis M, Weiss BG, Bertlich M. Lipopolysaccharide decreases cochlear blood flow dose dependently in a guinea pig animal model via TNF signaling. Microcirculation 2021; 28:e12681. [PMID: 33501679 DOI: 10.1111/micc.12681] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/15/2021] [Accepted: 01/20/2021] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To evaluate the effect of Lipopolysaccharide (LPS), a bacterial endotoxin on cochlear microcirculation, and its mode of action. METHODS Twenty-five Dunkin-Hartley guinea pigs were divided into five groups of five animals each. After surgical preparation, cochlear microcirculation was quantified by in vivo fluorescence microscopy. Placebo or LPS (1 mg, 10 µg, and 100 ng) was applied topically, and microcirculation was measured before and twice after application. A fifth group was pretreated with etanercept, a tumor necrosis factor (TNF) antagonist, and afterward the lowest LPS concentrations that yielded significant results (10 µg) were applied. RESULTS In the groups that had been treated with 1 mg and 10 µg LPS, a significant drop in cochlear microcirculation was observed after 30 (.791 ± .089 Arbitrary Units (AU), compared to baseline, and .888 ± .071AU) and 60 (.756 ± .101 AU and .817 ± .124 AU, respectively) minutes. The groups that had been treated with 100 ng LPS and that had been pretreated with etanercept showed no significant change in cochlear blood flow compared to placebo. CONCLUSION Lipopolysaccharide shows a dose-dependent effect on cochlear microcirculation; this effect can already be observed after 30 min. Pretreatment with etanercept can abrogate this effect, indicating that TNF mediates the effect of LPS on cochlear microcirculation.
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Affiliation(s)
- Friedrich Ihler
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Munich, Germany.,Walter Brendel Centre of Experimental Medicine, University of Munich Hospital, Munich, Germany
| | - Saskia Freytag
- Population Health and Immunity Division, Walter and Eliza Hall Institute, Parkville, Vic., Australia.,Department of Medical Biology, University of Melbourne, Melbourne, Vic., Australia
| | - Benedikt Kloos
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Munich, Germany.,Walter Brendel Centre of Experimental Medicine, University of Munich Hospital, Munich, Germany
| | - Jennifer Lee Spiegel
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Munich, Germany
| | - Frank Haubner
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Munich, Germany
| | - Martin Canis
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Munich, Germany.,Walter Brendel Centre of Experimental Medicine, University of Munich Hospital, Munich, Germany
| | - Bernhard G Weiss
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Munich, Germany.,Walter Brendel Centre of Experimental Medicine, University of Munich Hospital, Munich, Germany
| | - Mattis Bertlich
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University of Munich, Munich, Germany.,Walter Brendel Centre of Experimental Medicine, University of Munich Hospital, Munich, Germany
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Espinosa-Sanchez JM, Lopez-Escamez JA. The pharmacological management of vertigo in Meniere disease. Expert Opin Pharmacother 2020; 21:1753-1763. [DOI: 10.1080/14656566.2020.1775812] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Juan Manuel Espinosa-Sanchez
- Department of Otolaryngology, Instituto de Investigación Biosanitaria Ibs.GRANADA, Hospital Universitario Virgen de las Nieves, Universidad de Granada, Granada, Spain
- Otology & Neurotology Group CTS 495, Department of Genomic Medicine, GENYO. Centre for Genomics and Oncological Research: Pfizer/University of Granada/Andalusian Regional, Government PTS Granada, Granada, Spain
| | - José A. Lopez-Escamez
- Department of Otolaryngology, Instituto de Investigación Biosanitaria Ibs.GRANADA, Hospital Universitario Virgen de las Nieves, Universidad de Granada, Granada, Spain
- Otology & Neurotology Group CTS 495, Department of Genomic Medicine, GENYO. Centre for Genomics and Oncological Research: Pfizer/University of Granada/Andalusian Regional, Government PTS Granada, Granada, Spain
- Department of Surgery, Division of Otolaryngology, Universidad de Granada, Granada, Spain
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Basura GJ, Adams ME, Monfared A, Schwartz SR, Antonelli PJ, Burkard R, Bush ML, Bykowski J, Colandrea M, Derebery J, Kelly EA, Kerber KA, Koopman CF, Kuch AA, Marcolini E, McKinnon BJ, Ruckenstein MJ, Valenzuela CV, Vosooney A, Walsh SA, Nnacheta LC, Dhepyasuwan N, Buchanan EM. Clinical Practice Guideline: Ménière's Disease. Otolaryngol Head Neck Surg 2020; 162:S1-S55. [PMID: 32267799 DOI: 10.1177/0194599820909438] [Citation(s) in RCA: 127] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
OBJECTIVE Ménière's disease (MD) is a clinical condition defined by spontaneous vertigo attacks (each lasting 20 minutes to 12 hours) with documented low- to midfrequency sensorineural hearing loss in the affected ear before, during, or after one of the episodes of vertigo. It also presents with fluctuating aural symptoms (hearing loss, tinnitus, or ear fullness) in the affected ear. The underlying etiology of MD is not completely clear, yet it has been associated with inner ear fluid (endolymph) volume increases, culminating in episodic ear symptoms (vertigo, fluctuating hearing loss, tinnitus, and aural fullness). Physical examination findings are often unremarkable, and audiometric testing may or may not show low- to midfrequency sensorineural hearing loss. Conventional imaging, if performed, is also typically normal. The goals of MD treatment are to prevent or reduce vertigo severity and frequency; relieve or prevent hearing loss, tinnitus, and aural fullness; and improve quality of life. Treatment approaches to MD are many and typically include modifications of lifestyle factors (eg, diet) and medical, surgical, or a combination of therapies. PURPOSE The primary purpose of this clinical practice guideline is to improve the quality of the diagnostic workup and treatment outcomes of MD. To achieve this purpose, the goals of this guideline are to use the best available published scientific and/or clinical evidence to enhance diagnostic accuracy and appropriate therapeutic interventions (medical and surgical) while reducing unindicated diagnostic testing and/or imaging.
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Affiliation(s)
| | | | | | | | | | | | - Matthew L Bush
- University of Kentucky Medical Center, Lexington, Kentucky, USA
| | - Julie Bykowski
- University of California San Diego, San Diego, California, USA
| | - Maria Colandrea
- Duke University School of Nursing and Durham Veterans Affairs Medical Center, Durham, North Carolina, USA
| | | | | | - Kevin A Kerber
- University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | | | | | - Evie Marcolini
- Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Brian J McKinnon
- Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
| | | | | | | | - Sandra A Walsh
- Consumers United for Evidence-Based Healthcare, Baltimore, Maryland, USA
| | - Lorraine C Nnacheta
- American Academy of Otolaryngology-Head and Neck Surgery, Alexandria, Virginia, USA
| | - Nui Dhepyasuwan
- American Academy of Otolaryngology-Head and Neck Surgery, Alexandria, Virginia, USA
| | - Erin M Buchanan
- American Academy of Otolaryngology-Head and Neck Surgery, Alexandria, Virginia, USA
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Canis M, Bertlich M. Cochlear Capillary Pericytes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1122:115-123. [PMID: 30937866 DOI: 10.1007/978-3-030-11093-2_7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Capillary pericytes in the cochlea of mammals are-compared to pericytes in other tissues, like the CNS-relatively poorly researched. To begin with, there is still a considerable debate as to whether the very last precapillary arterioles should-due to their contractile properties-may be considered to be pericytes.However, cochlear capillary pericytes have shifted into the center of attention in the past decade. Most mammals show a considerable number of pericytes in the stria vascularis of the cochlea-up to 1300 in a mouse alone. This high number may be explained by the observation that cochlear capillary pericytes may be differentiated into different subgroups, depending on the immune markers that are expressed by them. Corresponding with these subpopulations, cochlear pericytes fulfill three core functions in the physiology of the cochlea: Formation of the intrastrial blood-fluid barrier-Pericytes monitor the ion, fluid, and nutrient household and aid in the homeostasis thereof. Regulation of cochlear blood flow-By contraction on relaxation, pericytes contribute to the regulation of cochlear blood flow, a paramount function parameter of the cochlea. Immune response-Pericytes actually contribute to the immune response in inflammation of the cochlea. Due to these central roles in the physiology of the cochlea, pericytes actually play a major role in numerous cochlear pathologies, including, but not limited to, sudden sensorineural hearing loss, acoustic trauma, and inflammation of the cochlea.
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Affiliation(s)
- Martin Canis
- The Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital, Munich, Germany
| | - Mattis Bertlich
- The Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital, Munich, Germany.
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Zyryanov SK, Butranova OI, Ramenskaya GV, Gildeeva GN, Shohin IE. [In vitro equivalence evaluation of betahistine generic medicinal products as a tool potentially determining the efficacy of pharmacotherapy]. Zh Nevrol Psikhiatr Im S S Korsakova 2018; 118:43-48. [PMID: 30585603 DOI: 10.17116/jnevro201811811143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
AIM To compare release parameters of various betahistine drugs in vitro using a comparative dissolution kinetics test. MATERIAL AND METHODS Objects of research are solid dosage forms (tablets) containing betahistine in a dose of 24 mg permitted for medical use in the Russian Federation. A method of comparative dissolution kinetics test was carried out as follows. The study was performed on a paddle stirrer at a speed of 50 rpm in three different pH dissolution media (pH 1.2, 4.5, 6.8), simulating the main sections of the digestive tract in which the active ingredient was decomposed, released and absorbed. This was performed in a quality controlled environment using a citrate buffer solution with pH 6.8. The time points for sampling the medium were 10 min, 15 min, 20 min and 30 min. RESULTS The results of betahistine release were significant (RSD<10%) for all time points, except the first time point (RSD<20%). Regardless of pH, there was a complete release (≥85% over 15 minutes, <10%) of betahistine from betaserc, 24 mg, tablets (manufactured by Mylan Laboratories SAS). The dissolution profiles of betahistine in other investigational drugs did not show complete drug release (parameter <85% in 15 minutes, <10%) in different pH media. Therefore, dissolution profiles of the studied drugs were not comparable to the reference profile. CONCLUSION Starting from 10 minutes, the reference drug of betahistine (betaserc, 24 mg) has a consistently higher release at different pH levels (representing the various stages of gastric digestion), vs. other studied generic analogues showing significantly lower levels of betahistine release. None of the studied drugs were found to be equivalent in vitro.
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Affiliation(s)
- S K Zyryanov
- Peoples' Friendship University of Russia, Medical Institute, Department of General and Clinical Pharmacology. Moscow, Russia
| | - O I Butranova
- Peoples' Friendship University of Russia, Medical Institute, Department of General and Clinical Pharmacology. Moscow, Russia
| | - G V Ramenskaya
- Sechenov First Moscow State Medical University, Moscow, Russia
| | - G N Gildeeva
- Sechenov First Moscow State Medical University, Moscow, Russia
| | - I E Shohin
- Center of Pharmaceutical Analytic Ltd., Moscow, Russia
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Nitrosalicylatocopper(II) complexes with chelating pyridine derivatives. ACTA CHIMICA SLOVACA 2018. [DOI: 10.2478/acs-2018-0004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
Three new nitrosalicylatocopper(II) complexes have been prepared and characterized. Compounds of the composition Cu(5-NSal)2(2-ampy)2 (1), Cu(5-NSal)2(2-hmpy)2 (2) and Cu(3,5-DNSal)2(2-hmpy)2 (3), where 2-ampy = (2-aminomethyl)pyridine, 2-hmpy = (2-hydroxymethyl)pyridine, 5-NSal = 5-nitrosalicylate anion and 3,5-DNSal = 3,5-dinitrosalicylate anion, were characterized by elemental analyses, EPR and IR spectroscopy. EPR spectra are consistent with the dx2-y2ground electronic state. Spectral properties have shown “classic” monodentate coordination of 5-nitrosalicylate anion. Similarly, bonding mode of the 3,5‑dinitrosalicylate anion in (3) is assumed to be unidentate via the carboxyl group, which is surprising compared with the previously studied complex, where the preferred coordination via the phenolate group anion was observed.
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Tighilet B, Léonard J, Watabe I, Bernard-Demanze L, Lacour M. Betahistine Treatment in a Cat Model of Vestibular Pathology: Pharmacokinetic and Pharmacodynamic Approaches. Front Neurol 2018; 9:431. [PMID: 29942281 PMCID: PMC6005348 DOI: 10.3389/fneur.2018.00431] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 05/22/2018] [Indexed: 11/13/2022] Open
Abstract
This study is a pharmacokinetic (PK) and pharmacodynamics (PD) approach using betahistine doses levels in unilateral vestibular neurectomized cats (UVN) comparable to those used in humans for treating patients with Menière's disease. The aim is to investigate for the first time oral betahistine administration (0.2 and 2 mg/kg/day) with plasma concentrations of betahistine and its major metabolite 2-pyridylacetic acid (2-PAA) (N = 9 cats), the time course of posture recovery (N = 13 cats), and the regulation of the enzyme synthesizing histamine (histidine decarboxylase: HDC) in the tuberomammillary nuclei (TMN) of UVN treated animals (N = the same 13 cats plus 4 negative control cats). In addition the effect of co-administration of the lower betahistine dose (0.2 mg/kg/day) and selegiline (1 mg/kg/day), an inhibitor of the monamine oxidase B (MAOBi) implicated in betahistine catabolism was investigated. The PK parameters were the peak concentration (Cmax), the time when the maximum concentration is reached (Tmax) for both betahistine and 2-PAA and the area under the curve (AUC). The PD approach consisted at quantifying the surface support area, which is a good estimation of posture recovery. The plasma concentration-time-profiles of betahistine and 2-PAA in cats were characterized by early Cmax-values followed by a phase of rapid decrease of plasma concentrations and a final long lasting low level of plasma concentrations. Co administration of selegiline and betahistine increased values of Cmax and AUC up to 146- and 180-fold, respectively. The lowest dose of betahistine (0.2 mg/kg) has no effects on postural function recovery but induced an acute symptomatic effect characterized by a fast balance improvement (4–6 days). The higher dose (2 mg/kg) and the co-administration treatment induced both this acute effect plus a significant acceleration of the recovery process. The histaminergic activity of the neurons in the TMN was significantly increased under treatment with the 2 mg/kg betahistine daily dose, but not with the lower dose alone or in combination with selegiline. The results show for the first time that faster balance recovery in UVN treated cats is accompanied with high plasma concentrations of betahistine and 2-PAA, and upregulation of HDC immunopositive neurons in the TMN. The higher betahistine dose gives results similar to those obtained with the lower dose when co-administrated with an inhibitor of betahistine metabolism, selegiline. From a clinical point of view, the study provides new perspectives for Menière's disease treatment, regarding the daily betahistine dose that should be necessary for fast and slow metabolizers.
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Affiliation(s)
- Brahim Tighilet
- Aix-Marseille Université - Centre National de la Recherche Scientifique, Laboratoire de Neurosciences Sensorielles et Cognitives, UMR 7260, Physiopathologie et Thérapie des Désordres Vestibulaires, Centre Saint-Charles, Marseille, France
| | - Jacques Léonard
- Aix-Marseille Université - Centre National de la Recherche Scientifique, Laboratoire de Neurosciences Sensorielles et Cognitives, UMR 7260, Physiopathologie et Thérapie des Désordres Vestibulaires, Centre Saint-Charles, Marseille, France
| | - Isabelle Watabe
- Aix-Marseille Université - Centre National de la Recherche Scientifique, Laboratoire de Neurosciences Sensorielles et Cognitives, UMR 7260, Physiopathologie et Thérapie des Désordres Vestibulaires, Centre Saint-Charles, Marseille, France
| | - Laurence Bernard-Demanze
- Aix-Marseille Université - Centre National de la Recherche Scientifique, Laboratoire de Neurosciences Sensorielles et Cognitives, UMR 7260, Physiopathologie et Thérapie des Désordres Vestibulaires, Centre Saint-Charles, Marseille, France.,Service ORL et de Chirurgie Cervico-Faciale Hôpital de la Conception Marseille, Marseille, France
| | - Michel Lacour
- Aix-Marseille Université - Centre National de la Recherche Scientifique, Laboratoire de Neurosciences Sensorielles et Cognitives, UMR 7260, Physiopathologie et Thérapie des Désordres Vestibulaires, Centre Saint-Charles, Marseille, France
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Bertlich M, Ihler F, Weiss BG, Freytag S, Strupp M, Canis M. Cochlear Pericytes Are Capable of Reversibly Decreasing Capillary Diameter In Vivo After Tumor Necrosis Factor Exposure. Otol Neurotol 2018; 38:e545-e550. [PMID: 29135875 DOI: 10.1097/mao.0000000000001523] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
OBJECTIVE The aim of this work was to evaluate the effect of tumor necrosis factor (TNF) and its neutralization with etanercept on the capability of cochlear pericytes to alter capillary diameter in the stria vascularis. METHODS Twelve Dunkin-Hartley guinea pigs were randomly assigned to one of three groups. Each group was treated either with placebo and then placebo, TNF and then placebo, or TNF and then etanercept. Cochlear pericytes were visualized using diaminofluorescein-2-diacetate and intravasal blood flow by fluorescein-dextrane. Vessel diameter at sites of pericyte somas and downstream controls were quantified by specialized software. Values were obtained before treatment, after first treatment with tumor necrosis factor or placebo and after second treatment with etanercept or placebo. RESULTS Overall, 199 pericytes in 12 animals were visualized. After initial treatment with TNF, a significant decrease in vessel diameter at sites of pericyte somas (3.6 ±4.3%, n = 141) compared with placebo and downstream controls was observed. After initial treatment with TNF, the application of etanercept caused a significant increase (3.3 ±5.5%, n = 59) in vessel diameter at the sites of pericyte somata compared with placebo and downstream controls. CONCLUSION We have been able to show that cochlear pericytes are capable of reducing capillary diameter after exposition to TNF. Moreover, the reduction in capillary diameter observed after the application of TNF is revertible after neutralization of tumor necrosis factor by the application of etanercept. It seems that contraction of cochlear pericytes contributes to the regulation of cochlear blood flow.
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Affiliation(s)
- Mattis Bertlich
- *Department of Otorhinolaryngology-Head and Neck Surgery, University Medical Center Göttingen, Göttingen, Germany †Population Health and Immunity Division, Walter and Eliza Hall Institute ‡Department of Medical Biology, University of Melbourne, Parkville, Australia §Department of Neurology, Munich University Hospital, Munich, Germany
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High-resolution MRI of the inner ear enables syndrome differentiation and specific treatment of cerebellar downbeat nystagmus and secondary endolymphatic hydrops in a postoperative ELST patient. J Neurol 2018; 265:48-50. [PMID: 29644399 DOI: 10.1007/s00415-018-8858-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 04/03/2018] [Accepted: 04/03/2018] [Indexed: 10/17/2022]
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Bertlich M, Ihler F, Weiss BG, Freytag S, Strupp M, Jakob M, Canis M. Role of capillary pericytes and precapillary arterioles in the vascular mechanism of betahistine in a guinea pig inner ear model. Life Sci 2017; 187:17-21. [DOI: 10.1016/j.lfs.2017.08.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 08/03/2017] [Accepted: 08/14/2017] [Indexed: 10/19/2022]
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Fingolimod (FTY-720) is Capable of Reversing Tumor Necrosis Factor Induced Decreases in Cochlear Blood Flow. Otol Neurotol 2017; 38:1213-1216. [DOI: 10.1097/mao.0000000000001510] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Adrion C, Fischer CS, Wagner J, Gürkov R, Mansmann U, Strupp M. Efficacy and safety of betahistine treatment in patients with Meniere's disease: primary results of a long term, multicentre, double blind, randomised, placebo controlled, dose defining trial (BEMED trial). BMJ 2016; 352:h6816. [PMID: 26797774 PMCID: PMC4721211 DOI: 10.1136/bmj.h6816] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
STUDY QUESTION What is the long term efficacy of betahistine dihydrochloride on the incidence of vertigo attacks in patients with Meniere's disease, compared with placebo? METHODS The BEMED trial is a multicentre, double blind, randomised, placebo controlled, three arm, parallel group, phase III, dose defining superiority trial conducted in 14 German tertiary referral centres (for neurology or ear, nose, and throat). Adults aged 21-80 years (mean age 56 years) with definite unilateral or bilateral Meniere's disease were recruited from March 2008 to November 2012. Participants received placebo (n=74), low dose betahistine (2 × 24 mg daily, (n=73)), or high dose betahistine (3 × 48 mg daily, (n=74)) over nine months. The primary outcome was the number of attacks per 30 days, based on patients' diaries during a three month assessment period at months seven to nine. An internet based randomisation schedule performed a concealed 1:1:1 allocation, stratified by study site. Secondary outcomes included the duration and severity of attacks, change in quality of life scores, and several observer-reported parameters to assess changes in audiological and vestibular function. STUDY ANSWER AND LIMITATIONS Incidence of attacks related to Meniere's disease did not differ between the three treatment groups (P=0.759). Compared with placebo, attack rate ratios were 1.036 (95% confidence interval 0.942 to 1.140) and 1.012 (0.919 to 1.114) for low dose and high dose betahistine, respectively. The overall monthly attack rate fell significantly by the factor 0.758 (0.705 to 0.816; P<0.001). The population based, mean monthly incidence averaged over the assessment period was 2.722 (1.304 to 6.309), 3.204 (1.345 to 7.929), and 3.258 (1.685 to 7.266) for the placebo, low dose betahistine, and high dose betahistine groups, respectively. Results were consistent for all secondary outcomes. Treatment was well tolerated with no unexpected safety findings. Without a control group of patients who did not receive any intervention to follow the natural course of the disease, the placebo effect could not be accurately assessed and differentiated from spontaneous remission and fluctuation of symptoms. WHAT THIS STUDY ADDS Current evidence is limited as to whether betahistine prevents vertigo attacks caused by Meniere's disease, compared with placebo. The trial provides information on symptom relief on placebo intervention which is relevant for the design of future studies on potential disease modifying treatments in patients with Meniere's disease. FUNDING, COMPETING INTERESTS, DATA SHARING Support from the German Federal Ministry of Education and Research (BMBF support code 01KG0708). Potential competing interests have been reported in full at the end of the paper on thebmj.com. Data are available from the corresponding author (Michael.Strupp@med.uni-muenchen.de) or biostatistician (mansmann@ibe.med.uni-muenchen.de). Study registration EudraCT no 2005-000752-32; ISRCTN no ISRCTN44359668.
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Affiliation(s)
- Christine Adrion
- German Center for Vertigo and Balance Disorders, University Hospital Munich, Campus Grosshadern, Munich, Germany Institute for Medical Informatics, Biometry, and Epidemiology, University of Munich, Campus Grosshadern
| | - Carolin Simone Fischer
- German Center for Vertigo and Balance Disorders, University Hospital Munich, Campus Grosshadern, Munich, Germany
| | - Judith Wagner
- Department of Neurology, University Hospital Munich, 81377 Munich
| | - Robert Gürkov
- Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Munich
| | - Ulrich Mansmann
- Institute for Medical Informatics, Biometry, and Epidemiology, University of Munich, Campus Grosshadern
| | - Michael Strupp
- German Center for Vertigo and Balance Disorders, University Hospital Munich, Campus Grosshadern, Munich, Germany Department of Neurology, University Hospital Munich, 81377 Munich
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Abstract
Menière's disease (MD) is a chronic multifactorial disorder of the inner ear characterized by episodic vestibular symptoms associated with sensorineural hearing loss, tinnitus, and aural pressure. Epidemiologic and genomic evidence supports a genetic susceptibility with multiple biochemical pathways involved, including the endocrine system, innate immune response, and autonomic nervous system. Allergens, infectious agents, vascular events, or genetic factors could modify inner-ear homeostasis and trigger MD. The diagnosis of MD is based on clinical criteria and requires the observation of an episodic vertigo syndrome associated with low- to medium-frequency sensorineural hearing loss and fluctuating aural symptoms (hearing loss, tinnitus, and/or fullness) in the affected ear. Headache is also found during the attacks and bilateral involvement is found in 25-40% of cases. Audiologic and vestibular assessment is recommended to monitor the clinical course. The treatment of MD is symptomatic to obtain relief of vestibular episodes and preventive to limit hearing loss progression. Treatment options include sodium restriction, betahistine, intratympanic gentamicin, or steroids and eventually surgery, such as cochlear implantation.
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Affiliation(s)
- J M Espinosa-Sanchez
- Otology and Neurotology Group, Department of Genomic Medicine, Centre for Genomics and Oncological Research (GENYO), Pfizer-University of Granada-Junta de Andalucia, Granada, Spain; Department of Otolaryngology, Hospital San Agustin, Linares, Jaen, Spain
| | - J A Lopez-Escamez
- Otology and Neurotology Group, Department of Genomic Medicine, Centre for Genomics and Oncological Research (GENYO), Pfizer-University of Granada-Junta de Andalucia, Granada, Spain; Department of Otolaryngology, Complejo Hospitalario Universitario de Granada, Granada, Spain.
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Strupp M, Dieterich M, Zwergal A, Brandt T. [Peripheral, central and functional vertigo syndromes]. DER NERVENARZT 2015; 86:1573-84; quiz 1585-6. [PMID: 26643594 DOI: 10.1007/s00115-015-4425-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Depending on the temporal course, three forms of vertigo syndrome can be differentiated: 1) vertigo attacks, e.g. benign paroxysmal positional vertigo (BPPV), Menière's disease and vestibular migraine, 2) acute spontaneous vertigo lasting for days, e.g. acute unilateral vestibulopathy, brainstem or cerebellar infarction and 3) symptoms lasting for months or years, e.g. bilateral vestibulopathy and functional vertigo. The specific therapy of the various syndromes is based on three principles: 1) physical treatment with liberatory maneuvers for BPPV and balance training for vestibular deficits, 2) pharmacotherapy, e.g. for acute unilateral vestibulopathy (corticosteroids) and Menière's disease (transtympanic administration of gentamicin or steroids and high-dose betahistine therapy); placebo-controlled pharmacotherapy studies are currently being carried out for acute unilateral vestibulopathy, vestibular paroxysmia, prophylaxis of BPPV, vestibular migraine, episodic ataxia type 2 and cerebellar ataxia; 3) psychotherapy for functional dizziness.
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Affiliation(s)
- M Strupp
- Neurologische Klinik, Klinikum der Universität München, Campus Großhadern, Marchioninistr. 15, 81377, München, Deutschland. .,Deutsches Schwindel- und Gleichgewichtszentrum, Klinikum der Universität München, Campus Großhadern, München, Deutschland.
| | - M Dieterich
- Neurologische Klinik, Klinikum der Universität München, Campus Großhadern, Marchioninistr. 15, 81377, München, Deutschland.,Deutsches Schwindel- und Gleichgewichtszentrum, Klinikum der Universität München, Campus Großhadern, München, Deutschland.,SyNergy, Munich Cluster for Systems Neurology, München, Deutschland
| | - A Zwergal
- Neurologische Klinik, Klinikum der Universität München, Campus Großhadern, Marchioninistr. 15, 81377, München, Deutschland.,Deutsches Schwindel- und Gleichgewichtszentrum, Klinikum der Universität München, Campus Großhadern, München, Deutschland
| | - T Brandt
- Deutsches Schwindel- und Gleichgewichtszentrum, Klinikum der Universität München, Campus Großhadern, München, Deutschland.,Institut für Klinische Neurowissenschaften, Klinikum der Universität München, Campus Großhadern, München, Deutschland
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Strupp M, Zwergal A, Feil K, Bremova T, Brandt T. Pharmacotherapy of vestibular and cerebellar disorders and downbeat nystagmus: translational and back-translational research. Ann N Y Acad Sci 2015; 1343:27-36. [PMID: 25903394 DOI: 10.1111/nyas.12774] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
There are currently eight groups of drugs for the pharmacotherapy of vertigo, nystagmus, and cerebellar disorders: antiemetics; anti-inflammatories, antimenieres, and antimigraineous medications; antidepressants, anticonvulsants, aminopyridines, and acetyl-DL-leucine ("the eight A's"). In acute unilateral vestibulopathy, corticosteroids improve the recovery of peripheral vestibular function, but there is not sufficient current evidence for a general recommendation. There is also insufficient evidence that 48 or 144 mg/day betahistine has an effect in Ménière's disease. Therefore, higher dosages are currently recommended; in animal studies, it was shown that betahistine increases cochlear blood flow. In vestibular paroxysmia, oxcarbazepine was effective (one yet not randomized controlled trial (RCT)). Aminopyridines are recommended for the treatment of downbeat nystagmus (two RCTs) and episodic ataxia type 2 (EA2, one RCT). There are so far no RCTs on vestibular migraine, so currently no treatment can be recommended. Acetyl-dl-leucine improves cerebellar ataxia (three observational studies); it also accelerates central compensation in an animal model of acute unilateral lesion, but RCTs were negative. There are ongoing RCTs on vestibular paroxysmia with carbamazepine (VESPA), acute unilateral vestibulopathy with betahistine (BETAVEST), vestibular migraine with metoprolol (PROVEMIG), benign paroxysmal positional vertigo with vitamin D (VitD@BPPV), EA2 with 4-aminopyridine versus acetazolamide (EAT-2-TREAT), and cerebellar ataxias with acetyl-DL-leucine (ALCAT).
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Affiliation(s)
- Michael Strupp
- Department of Neurology, German Center for Vertigo and Balance Disorders and Institute for Clinical Neurosciences, University Hospital Munich, Campus Grosshadern, Munich, Germany
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Two-photon microscopy allows imaging and characterization of cochlear microvasculature in vivo. BIOMED RESEARCH INTERNATIONAL 2015; 2015:154272. [PMID: 25883941 PMCID: PMC4390612 DOI: 10.1155/2015/154272] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 02/26/2015] [Accepted: 03/02/2015] [Indexed: 11/18/2022]
Abstract
Impairment of cochlear blood flow has been discussed as factor in the pathophysiology of various inner ear disorders. However, the microscopic study of cochlear microcirculation is limited due to small scale and anatomical constraints. Here, two-photon fluorescence microscopy is applied to visualize cochlear microvessels. Guinea pigs were injected with Fluorescein isothiocyanate- or Texas red-dextrane as plasma marker. Intravital microscopy was performed in four animals and explanted cochleae from four animals were studied. The vascular architecture of the cochlea was visualized up to a depth of 90.0±22.7 μm. Imaging yielded a mean contrast-to-noise ratio (CNR) of 3.3±1.7. Mean diameter in vivo was 16.5±6.0 μm for arterioles and 8.0±2.4 μm for capillaries. In explanted cochleae, the diameter of radiating arterioles and capillaries was measured with 12.2±1.6 μm and 6.6±1.0 μm, respectively. The difference between capillaries and arterioles was statistically significant in both experimental setups (P<0.001 and P=0.022, two-way ANOVA). Measured vessel diameters in vivo and ex vivo were in agreement with published data. We conclude that two-photon fluorescence microscopy allows the investigation of cochlear microvessels and is potentially a valuable tool for inner ear research.
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