A rapid simultaneous antigen detection of Haemophilus influenzae and Streptococcus pneumoniae for predicting the prognosis of acute otitis media.

BACKGROUND: Rapid identification of causative bacteria in treatment of acute otitis media (AOM) is of paramount importance for appropriate antibiotic use. MATERIALS AND METHODS: This prospective observational study was conducted in 15 hospitals and clinics in Japan between 2018 and 2020. A new rapid antigen test kit (AOS-116), which simultaneously detects antigens for Streptococcus pneumoniae (Sp) and Haemophilus influenzae (Hi), was applied for middle ear fluids (MEFs) and nasopharyngeal secretions (NPSs) in patients with moderate to severe AOM. We investigated relationship between the results of rapid test, severity at initial visit, and clinical course. RESULTS: Regarding performance accuracy based on culture results, AOS-116 showed 1) high (>80%) sensitivity, specificity, and negative predictive value (NPV) in MEFs for both antigens, 2) high sensitivity, specificity, and positive predictive value (PPV) in NPSs for Hi antigen, and 3) high specificity, and PPV in NPSs for Sp antigen. Regarding predictive value of nasopharyngeal culture and antigen detection for causative middle ear pathogens, similar results were observed between AOS-116 and culture, which was characterized with high sensitivity and NPV for both pathogens. MEFs/NPSs positive for Hi antigen were significantly associated with eardrum findings, and severity. MEFs/NPSs positive for pneumococcal antigen were significantly associated with severity of otalgia, fever, and otorrhea. Among patients with prior antimicrobial treatment, improvement tended to be slower in cases positive for Hi than in cases negative. CONCLUSION: The rapid antigen detection test is useful as a decision-making tool for prescribing antimicrobial agents and may play an important role in promoting appropriate antimicrobial use.

Microbiology of Acute Maxillary Sinusitis in Children.

OBJECTIVES/HYPOTHESIS: Acute rhinosinusitis is a frequent common cold-related complication in children. Despite the need for appropriate treatment, its underlying microbiology remains unclear. This study aimed to investigate the microbiology of acute rhinosinusitis in children. STUDY DESIGN: Prospective non controlled study. METHODS: Thirty-one pediatric acute maxillary sinusitis patients with severe symptoms were assessed. The subjects were 17 males and 14 females aged 5 to 14 years (mean age, 9.1 years). Maxillary sinus aspirates were collected and cultured, with subsequent viral and bacterial polymerase chain reaction (PCR) analysis. Bacteria were analyzed using culturing and PCR, and viruses were analyzed using PCR. The PCR kits used identify 18 types of respiratory viruses and 13 types of bacteria. RESULTS: At least one pathogen was detected in 30 of 31 aspirates (97%) using PCR, and none of the aspirates contained respiratory viruses alone. Ten aspirates (32%) contained both viruses and bacteria. The most common viruses detected were rhinovirus (13%) and influenza virus (10%). The most common bacteria were Haemophilus influenzae (45%), Streptococcus pneumoniae (32%), Moraxella catarrhalis (16%), and Chlamydophila pneumoniae (13%). Bacteria were found in 21 of 31 cases (68%) via bacterial culturing. Culturing revealed that H influenzae was the most common pathogen (42%). CONCLUSIONS: In pediatric acute maxillary sinusitis, respiratory bacteria were detected in 65% of the sinus aspirates and both bacteria and viruses in 32%. The most common viruses were rhinovirus and influenza virus, and the most common bacteria were H influenzae and S pneumoniae. Viral and bacterial PCR is useful for accurately investigating the microbiology in pediatric sinusitis. LEVEL OF EVIDENCE: 3 Laryngoscope, 131:E2705-E2711, 2021.

Features predicting treatment failure in pediatric acute otitis media.

OBJECTIVES: To facilitate better antibiotic stewardship, we conducted this clinical trial to identify the prognostic features of treatment failure in pediatric acute otitis media (AOM). STUDY: Design: This is a randomized, parallel-group, open-label, comparative clinical trial. SUBJECTS AND METHODS: Children with AOM and aged between 1 month and 5 years were enrolled. Patients were randomly assigned to receive either amoxicillin alone (70 mg/kg) for five days, or the same with additional clarithromycin (15 mg/kg) for the initial three days. The clinical course of AOM was evaluated based on tympanic membrane scores. Failure of treatment for AOM was confirmed on day 14. Nasal conditions were also assessed by a clinical scoring system for acute rhinosinusitis. RESULTS: Treatment failures occurred in 25 out of 129 (19.4%) children. The ratio of treatment failures by age was significantly higher in children younger than 2 years than in children older than 2 years. The tympanic membrane scores on day 3 (P = 0.0334) and day 5 (P < 0.0001) and acute rhinosinusitis scores on day 5 (P = 0.0004) were higher in failure cases than in cured cases. Multivariate logistic regression analysis indicated significant associations between the treatment failure with tympanic membrane scores and acute rhinosinusitis scores on day 5, and the antimicrobial treatment regimen. CONCLUSIONS: Improvement of acute rhinosinusitis and tympanic membrane scores on day five were important predictive features in failure of treatment for pediatric AOM. These results will be useful when discussing the treatment decisions with the patient's parents.

Clinical practice guidelines for the diagnosis and management of acute otitis media in children-2018 update.

OBJECTIVE: "Clinical Practice Guidelines for the Diagnosis and Management of Acute Otitis Media in Children-2018 update (2018 Guidelines)" aim to provide appropriate recommendations about the diagnosis and management of children with acute otitis media (AOM), including recurrent acute otitis media (recurrent AOM), in children under 15 years of age. These evidence-based recommendations were created with the consensus of the subcommittee members, taking into consideration unique characteristics of bacteriology and antimicrobial susceptibilities of AOM pathogens in Japan, as well as global advances in vaccines. METHODS: The subcommittee re-evaluated key clinical issues based on SCOPE (a master plan of the guidelines) and created clinical questions (CQ) about the diagnosis and management of AOM patients. A literature search of the publications from 2013 to 2016 were added to the Guidelines 2013, not only to assess the evidence on the effectiveness of vaccines, but also to provide up to date information of the bacteriology and antimicrobial susceptibilities of AOM causative pathogens in Japan. RESULTS: We have proposed guidelines for disease severity-based management of AOM patients, after classifying AOM severity into mild, moderate, and severe, based on age, clinical manifestations, and otoscopic findings. CONCLUSIONS: Precise otoscopic findings are essential for judging AOM severity, which can lead to appropriate management of AOM patients.

Comprehensive Detection of Respiratory Bacterial and Viral Pathogens in the Middle Ear Fluid and Nasopharynx of Pediatric Patients With Acute Otitis Media.

BACKGROUND: Acute otitis media (AOM) is a common ear infection caused by respiratory viruses and bacteria of the nasopharynx. The present study aimed to detect various respiratory viruses and bacteria in middle ear fluid (MEF) and nasopharyngeal aspirates (NPA) using polymerase chain reaction (PCR). METHODS: We collected MEF and NPA samples from 122 pediatric patients with AOM. Real-time PCR detected 11 types of respiratory viruses (respiratory syncytial virus A/B, parainfluenza virus 1/2/3, human metapneumovirus, influenza virus A/B, adenovirus, human bocavirus and rhino virus) and 7 types of bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydia pneumoniae, Streptococcus pyogenes, Legionella pneumophila and Moraxella catarrhalis). MEF specimens were also examined using bacterial culture. RESULTS: At least 1 respiratory viral or bacterial pathogen was detected in MEF of 120 cases (98%) by viral and bacterial PCR and of 93 cases (76%) by viral PCR and bacterial culture. Respiratory viruses were detected in NPA of 84 cases (69%) and MEF of 67 cases (55%). The most common virus detected in MEF was respiratory syncytial virus (21%), followed by parainfluenza virus (15%). All the viruses present in MEF were also detected in NPA specimens. Bacteria were detected by PCR in MEF of 109 cases (89%); H. influenzae was the most frequently detected (65%). CONCLUSIONS: In many cases, pediatric AOM was found to constitute a respiratory polymicrobial infection. Multiplex PCR was useful to detect multiple respiratory viruses and bacteria in AOM. To understand intractable AOM, further studies regarding the clinical features of each viral and bacterial coinfection are required.

Safety and efficacy of adenotonsillectomy for obstructive sleep apnea in infants, toddlers and preschool children.

OBJECTIVE: To investigate and compare the safety and efficacy of adenotonsillectomy (AT) on obstructive sleep apnea (OSA) in infants and toddlers (IT) with preschool children (PS), and charts of 147 children between the ages of 11 months and 6 years were reviewed. METHODS: Harmonic Scalpel (HS) was introduced into AT to reduce the operative duration and intraoperative hemorrhage. Preoperative and postoperative apnea-hypopnea indices (AHI) values obtained by the type 3 portable monitoring device, and the change achieved by AT were statistically compared between IT group (N=50) and PS group (N=97). The mean operative duration, the mean amount of intraoperative hemorrhage, the incidence of postoperative hemorrhage, the frequency of abnormal postoperative chest X-ray findings, and the length of hospital stay were also compared between the two groups. All statistical analyses were conducted using either the Student's t test or Fischer's exact test, and p-values <0.05 were considered statistically significant. RESULTS: In the IT group, the mean preoperative AHI value was 13.5±7.1 and decreased to 4.7±3.4 postoperatively. In the PS group, the mean AHI value changed from 16.0±10.2 to 4.4±2.4. There were statistically significant differences between the preoperative and postoperative AHI values in both the IT and PS groups, but there were no statistically significant differences between the IT and PS groups. The mean operative durations in the IT group for tonsillectomy and adenoidectomy were 12.8±6.7 min and 19.5±8.1 min, respectively. The corresponding values in the PS group were 14.5±6.6 min and 22.9±9.7 min, respectively. The mean tonsillectomy durations were comparable, but the adenoidectomy duration was statistically shorter in the IT group. In the IT group, the mean amounts of intraoperative hemorrhage during tonsillectomy and during adenoidectomy were 6.0±5.1 and 18.9±10.6 g, respectively. The corresponding values in the PS group were 6.4±5.4 g and 26.2±13.4 g, respectively. The mean tonsillectomy blood loss was comparable between the groups but was statistically less during adenoidectomy in the IT group. There were no statistical differences between the two groups in the incidence of postoperative hemorrhage and of abnormal findings in the postoperative chest X-ray, and in the length of hospital stay. CONCLUSION: AT in IT can be performed without major perioperative complications and should be considered the primary treatment of OSA from infancy to early childhood. Ultrasonic devices may contribute to increasing the safety of this surgical treatment.

An application of outer membrane protein p6-specific enzyme-linked immunosorbent assay for detection of haemophilus influenzae in middle ear fluids and nasopharyngeal secretions.

An enzyme-linked immunosorbent assay specific to outer membrane protein P6 (P6-ELISA) was applied for detecting Haemophilus influenzae in middle ear fluids (MEFs) from acute otitis media (AOM) patients and in nasopharyngeal secretions (NPSs) from acute rhinosinusitis patients. P6-ELISA had a sensitivity of 83.3% for MEFs and 71.5% for NPSs and a specificity of 85.6% for MEFs and 92.5% for NPSs, respectively. Real-time PCR exhibited significant differences in the number of ompP1 gene copies among samples determined by P6-ELISA to be positive and negative for H. influenzae. However, because the P6-ELISA test has the reactivity in Haemophilus species include two commensals H. haemolyticus and H. parainfluenzae, it is thus a weak method in order to detect only NTHi correctly. Consequently, diagnosis using the P6-ELISA should be based on an overall evaluation, including the results of other related examinations and clinical symptoms to prevent misleading conclusions in clinical setting.

Evaluation of a rapid immunochromatographic ODK-0901 test for detection of pneumococcal antigen in middle ear fluids and nasopharyngeal secretions.

Since the incidence of penicillin-resistant Streptococcus pneumoniae has been increasing at an astonishing rate throughout the world, the need for accurate and rapid identification of pneumococci has become increasingly important to determine the appropriate antimicrobial treatment. We have evaluated an immunochromatographic test (ODK-0901) that detects pneumococcal antigens using 264 middle ear fluids (MEFs) and 268 nasopharyngeal secretions (NPSs). A sample was defined to contain S. pneumoniae when optochin and bile sensitive alpha hemolytic streptococcal colonies were isolated by culture. The sensitivity and specificity of the ODK-0901 test were 81.4% and 80.5%, respectively, for MEFs from patients with acute otitis media (AOM). In addition, the sensitivity and specificity were 75.2% and 88.8%, respectively, for NPSs from patients with acute rhinosinusitis. The ODK-0901 test may provide a rapid and highly sensitive evaluation of the presence of S. pneumoniae and thus may be a promising method of identifying pneumococci in MEFs and NPSs.

Diagnostic value of plasma antidiuretic hormone, electrocochleography, and glycerol test in patients with endolymphatic hydrops.

OBJECTIVE: To investigate the relationship between the plasma antidiuretic hormone (p-ADH) level, electrocochleogram (ECoG), and the glycerol test in patients with endolymphatic hydrops (ELH). PATIENTS AND METHODS: The subjects were 60 patients, including 51 with Ménière's disease (except for cochlear Ménière's disease), 7 with delayed ELH, and 2 with syphilitic ELH. The time period for measurements of the p-ADH level, ECoG and the glycerol test was within 4 weeks. RESULTS: 13 patients showed positive results for all tests. 58 patients showed positive results for at least one of three tests. Only 2 patients showed negative results for all tests. CONCLUSION: The p-ADH level, ECoG and the glycerol test show different selectivity of ELH detection. It is useful to perform all three tests to diagnose ELH.

Ouabain-induced vacuolar formation in marginal cells in the stria vascularis is dependent on perilymphatic Na(+).

In the stria vascularis (SV), it is known that the Na(+)-K(+)-ATPase is expressed abundantly and its activity in the basolateral membrane of marginal cells is high. Ouabain, an inhibitor of the Na(+)-K(+)-ATPase, causes not only a decline in the endocochlear DC potential but also acute vacuolar formation in marginal cells. We studied the ionic mechanisms underlying the ouabain-induced vacuolar formation in marginal cells using perilymphatic perfusion in guinea pigs. Perilymphatic perfusion with 1 mM ouabain dissolved in the artificial perilymph for 50 min caused many vacuoles of a wide range of sizes in the apical cytoplasm of marginal cells, the bulging of marginal cells into the scala media and strial volume increase. Removal of K(+) from the perilymph reduced the proportion of vacuoles and strial thickening, but the bulging of marginal cells remained. In contrast, the sizes of vacuoles were drastically reduced and extrusion of marginal cells into the scala media could not be observed in the absence of perilymphatic Na(+). Furthermore, the total volume of SV was obviously reduced in comparison with the control. These results indicate that perilymphatic Na(+) and K(+) are responsible for these morphological changes caused by ouabain, and that perilymphatic Na(+) plays an important role in the cellular volume regulation in SV in the presence of ouabain. It is supposed that the transport system of perilymphatic Na(+) and K(+) into marginal cells may contribute to vacuolar formation when ouabain is administered. Regarding Na(+), we hypothesize two possibilities for the perilymphatic Na(+) transporting pathway as follows. Na(+) in the perilymph could enter the endolymph via Reissner's membrane or the basilar membrane; Na(+) in the endolymph would then be taken up by marginal cells via the apical membrane and secreted into the intrastrial space by Na(+)-K(+)-ATPase in the basolateral membrane. Another, less likely, possibility is that Na(+) in the perilymph is transported into basal cells or fibrocytes in the spiral ligament, then into intermediate cells via gap junctions, and finally secreted into the intrastrial space via Na(+)-K(+)-ATPase of intermediate cells. Regarding K(+), it is expected that the K(+) recycling pathway plays a role in ouabain-induced vacuolar formation in marginal cells.

Modification of surgical procedures of type 1 tympanoplasty for non-cholesteatomatous chronic otitis media.

OBJECTIVE: To introduce our modified procedures of type 1 tympanoplasty and to assess their efficacy. METHODS: We modified the surgical procedures of type 1 tympanoplasty and have used these procedures since September 1999. The modified points are enlargement of the facial recess approach, no elevation of the posterior meatal skin and the tympanic annulus, and endoaural repair of tympanic membrane perforation. 51 patients with simple chronic otitis media have undergone this modified type 1 tympanoplasty. Postoperative hearing was evaluated according to the criteria proposed by the Otological Society of Japan. RESULTS: The average follow-up period was 15 months (range 6-35). The hearing result was considered successful when the postoperative hearing level satisfied with at least one of three conditions as follows: (1) air-bone gap <15 dB, (2) hearing gain >15 dB, or (3) hearing level >30 dB. The success rate was 94.1%. The average postoperative air-bone gap, hearing gain and hearing level were 3.9, 10.0 and 29.3 dB, respectively. CONCLUSION: Our modified tympanoplasty is useful to achieve better postoperative hearing results.

Antidiuretic hormone and osmolality in isosorbide therapy and glycerol test.

Changes in plasma antidiuretic hormone (p-ADH) and plasma osmolality (p-Osm) levels were studied in 63 patients with Ménière's disease before and after isosorbide administration and a glycerol test. Increments in both p-ADH and p-Osm levels were observed after isosorbide administration and the glycerol test. The p-ADH secretion appeared to be secondarily stimulated by an increase in the p-Osm level. This p-ADH level increase affects cochlear fluid homeostasis. Based on these results, we must consider both the p-Osm and p-ADH levels when treating patients with Ménière's disease by osmotic diuretics.

The effects of basic fibroblast growth factor on postoperative mastoid cavity problems.

OBJECTIVES: To present the effects of basic fibroblast growth factor on intractable cavity problems and discuss the mechanisms of its effects. METHODS: We treated three ears with postoperative open cavities. All three cases had suffered from chronic discharge of the ear for 7, 10, and 30 years, respectively; 100 microg/ml of trafermin (genetic recombination) solution, as basic fibroblast growth factor, was dropped into the open cavity once daily. If bacterial and/or fungal infection was observed, antibiotics and/or antifungal agents were administered locally twice daily. RESULTS: The cavities epithelialized and were cured within 2 months using this treatment. CONCLUSION: Our results suggest that basic fibroblast growth factor stimulates the proliferation and differentiation of keratinocytes, fibroblasts, and endothelial cells, leading to accelerated wound healing. The basic fibroblast growth factor agent appears to be highly effective in treating intractable cavity problems.

Immunohistochemical localization of histamine receptors in rat cochlea.

OBJECTIVE: Histamine may have physiologic functions in the inner ear. The locations of histamine receptors, however, have not yet been identified in the mammalian cochlea. The aim of this study was to investigate the localization of histamine receptor subtypes (H1, H2, and H3 receptors) in rat cochlea. METHODS: Immunohistochemistry was performed with antibodies specific for each of the histamine receptors (H1, H2, and H3). To identify the type I and II spiral ganglion cells in the cochlea, some cryostat sections were double stained with antibodies to both a histamine receptor and neurofilament 200 kD, which predominantly stains type II spiral ganglion cells in the cochlea. RESULTS: All H1, H2, and H3 receptor immunoreactive staining was limited to the spiral ganglion cells of the cochlea. Spiral ganglion cells with positive immunoreactivity to the neurofilament 200 kD antibody were stained only slightly by histamine H1, H2, and H3 receptor antibodies, indicating that histamine receptor immunoreactivity is specific to type I ganglion cells. CONCLUSIONS: These findings indicate that histamine receptors are present in the cochlea and support the hypothesis that histamine plays a physiologic role in the cochlea.

Time course of dehydrating effects of isosorbide on experimentally induced endolymphatic hydrops in guinea pigs.

Osmotic diuretics are therapeutic agents used to reduce endolymphatic hydrops. However, glycerol-induced change in endolymph volume is followed by a rebound phenomenon. In this study, we investigated the rebound phenomenon occurring with isosorbide, an osmotic diuretic used as a therapeutic agent for Ménière's disease in Japan. Forty guinea pigs underwent surgical obliteration of the endolymphatic sac. Thirty received isosorbide orally 1 month after surgery. These animals were sacrificed 3, 6, or 12 h after isosorbide intake. The remaining 10 animals served as controls. Quantitative assessment of changes in the endolymphatic space was performed light-microscopically. Isosorbide reduced cochlear endolymph volume, with a peak reduction 6 h after intake. Thereafter, no prominent rebound phenomenon was noted. Clinically, since isosorbide is orally administered every 8 h, rebound phenomenon need not be considered in the treatment with isosorbide.

Bumetanide-induced enlargement of the intercellular space in the stria vascularis critically depends on Na+ transport.

The intercellular space in the stria vascularis (intrastrial space) is a closed space and isolated from both the endolymph and the perilymph in normal tissue. Loop diuretics such as bumetanide and furosemide cause an acute enlargement of the intrastrial space in association with a decline in the endocochlear potential. It is known that bumetanide inhibits the Na+-K+-2Cl- cotransporter, which is expressed abundantly in the basolateral membrane of marginal cells. We studied ionic mechanisms underlying the bumetanide-induced enlargement of the intrastrial space using perilymphatic perfusion in guinea pigs. Perilymphatic perfusion with artificial perilymph containing 100 microM bumetanide caused marked enlargement of the intrastrial space, as reported previously. Removal of K+ from the perilymph did not affect the bumetanide-induced enlargement, whereas removal of Na+ from the perilymph inhibited it almost completely. Perilymph containing 1 mM amiloride also inhibited the enlargement of the intrastrial space almost completely. These results indicate that perilymphatic Na+, but not K+, and amiloride-sensitive pathways are essential to the bumetanide-induced enlargement of the intrastrial space. Two possible pathways could yield these results. Na+ in the perilymph could enter the endolymph via Reissner's membrane or the basilar membrane; Na+ in the endolymph would then be taken up by marginal cells via the apical membrane and secreted into the intrastrial space by Na+-K+-ATPase in the basolateral membrane of them. Another, less likely possibility is that Na+ in the perilymph is transported into basal cells or fibrocytes in the spiral ligament, then into intermediate cells via gap junctions, and finally secreted into the intrastrial space via Na+-K+-ATPase of intermediate cells.

Electrocochleographic findings in cases of autoimmune disease with sensorineural deafness.

OBJECTIVES: To present electrocochleographic findings in patients with autoimmune disease (AD) with sensorineural deafness (ADSD), and to discuss the etiologies of sensorineural hearing loss (SNHL) in cases of ADSD. METHODS: Study design is a retrospective review of electrocochleographic results of 26 patients with ADSD. To evaluate the electrocochleographic results, average SP/AP ratios were compared between ADSD and normal subjects. In the ADSD group, audiologic pattern, fluctuations in hearing and results of the glycerol test were also reviewed. Electrocochleography (ECoG) was recorded using the extratympanic method, and the SP to AP ratio (SP/AP ratio) was analyzed. RESULTS: The mean of average SP/AP ratios in the ADSD groups (0.46) was significantly higher than that in normal subjects (0.27). Further, 17 of 29 affected ears in patients with ADSD showed fluctuating hearing loss. Eighteen ears showed low tone loss (rising and peak audiologic patterns). Only 5 of 26 ears (19.2%) showed positive results on glycerol test. There was no correlation between glycerol test results and hearing fluctuation or between glycerol test results and the SP/AP ratio on chi(2)-test. There was no tendency between audiologic pattern and glycerol test results or between audiologic pattern and the SP/AP ratio. CONCLUSION: These results suggest the etiologies of SNHL in cases of ADSD remain unclear. However, some cases showed clinical findings similar to endolymphatic hydrops. We should bear in mind that clinical Meniere's syndrome involves ADSD. Further investigation is needed to resolve the etiology of SNHL of ADSD.

The effects of V2 antagonist (OPC-31260) on endolymphatic hydrops.

In the present study, two experiments were performed to investigate the influence of OPC-31260 on experimentally induced endolymphatic hydrops in guinea pigs and the regulation of aquaporin-2 (AQP2) mRNA expression in the rat inner ear. In morphological studies, the increases in the ratios of the length of Reissner's membrane (IR-L) and the cross-sectional area of the scala media (IR-S) were quantitatively assessed among normal guinea pigs (normal ears) and three groups with hydropic ears: hydropic ears with no infusion (non-infusion hydropic ears), hydropic ears with an infusion of physiological saline into the scala tympani (saline-infused hydropic ears) and hydropic ears with infusion of 0.3% OPC-31260 into the scala tympani (OPC-infused hydropic ears). IR-Ls in the experimental groups were markedly larger than in the normal ear group, but there was no significant difference among the groups of non-infusion hydropic ears, saline-infused hydropic ears and OPC-infused hydropic ears. The IR-Ss of non-infusion hydropic ears and saline-infused hydropic ears (48.8-49.3%) were statistically different from that of normal ears (6.5%) (Dunnet multiple comparison test, P<0.01). However, IR-S of the OPC-infused hydropic ears (-14.8%) was significantly smaller than those of non-infusion hydropic ears and saline-infused hydropic ears (one-way ANOVA, P<0.01). In the quantitative polymerase chain reaction study, a comparison of the ratio of AQP2 and beta-actin mRNA (MAQP2/Mbeta-actin) was made between water-injected and OPC-31260-injected rats. An intravenous injection of OPC-31260 resulted in a significant decrease in MAQP2/Mbeta-actin both in the cochlea and in the endolymphatic sac (t-test, P<0.001). These results indicate that water homeostasis in the inner ear is regulated via the vasopressin-AQP2 system, and that the vasopressin type-2 antagonist OPC-31260 is a promising drug in the treatment of Meniere's disease.

Aquaporin-1 (AQP1) is expressed in the stria vascularis of rat cochlea.

Cochlea endolymph, produced by the stria vascularis, is essential for normal inner ear function. Abnormal endolymphatic volumes correlate closely with pathological conditions such as Ménière's disease. The critical roles played by aquaporins, which facilitate osmotic movement of water molecules, are known in a variety of tissues. We investigated the expression of aquaporin-1 (AQP1) in the rat inner ear using reverse transcription polymerase chain reaction and immunohistochemical methods. We obtained novel data showing that not just AQP1 mRNA but also AQP1 protein is expressed in the stria vascularis, in addition to other data confirming previous reports. AQP1 immunoreactivity localized to the intermediate cells in the stria vascularis. The above finding suggests that AQP1 may play a role in the water distribution associated with vigorous ion transport in the stria vascularis since the intermediate part of the stria vascularis contains both intermediate cells and the basolateral parts of marginal cells, both of which express ion transporters abundantly.

Expression of mRNA encoding the H1, H2, and H3 histamine receptors in the rat cochlea.

Histamine may have physiological functions in the inner ear. Histamine receptors, however, have not yet been identified in the mammalian cochlea. We determined, using reverse transcription polymerase chain reaction (RT-PCR), that H1, H2, and H3 histamine receptor mRNA is expressed in the rat cochlea. To investigate the distribution of each receptor, the cochlea was divided into three parts: the lateral portion, the medial portion, and the modiolus. The mRNA for each receptor subtype was detected in the modiolus but not in the lateral and medial portions of the cochlea. This is the first evidence of H1, H2, and H3 histamine receptor mRNA in the rat cochlea. These findings support the suggestion that histamine may play a physiological role in the cochlea.