[Hearing rehabilitation in postmeningitis deafness in the context of the time factor]. / Agyhártyagyulladás okozta súlyos fokú sensorineuralis halláscsökkenés rehabilitációs esélyei az idofaktor tekintetében.

INTRODUCTION: Postmeningitis deafness appears in 0-11% of the meningitis cases. Cochlear ossification can develop in these patients, which may make the hearing rehabilitation impossible with cochlear implantation. Due to ossification, it is critical to refer patients to the implant centre without any delay. OBJECTIVE: The aim of this study was to examine the time factor between the appearance of deafness and the first examination in a cochlear implant centre, the possibilities and effectivity of hearing rehabilitation. METHOD: In our tertial referral centre, postmeningitis deafened patients were examined between 2014 and 2022 retrospectively. Hearing results, imaging, possibilities of rehabilitation, complications of cochlear implantations and the hearing results were investigated. RESULTS: 8 patients (3 children, 5 adults) were investigated. The time between the start of deafness and the first appearance varied between 3 weeks to 9 years. Bilateral profound hearing loss was measured in all patients. In 6 cases, cochlear ossification was observed (4 patients bilateral). Cochlear implantation was conducted in 5 patients (4 bilateral, 1 unilateral). In 3 cases, implantation was impossible due to severe ossification. Hearing results showed good hearing levels with poor speech perception in all cases. DISCUSSION: The rehabilitation of severe hearing loss caused by meningitis can present many challenges to clinicians. A critical point in the care is the urgent referral of patients to a cochlear implantation centre as soon as possible after the life-threatening condition has passed. The implementation of further diagnostic and the earliest possible implantation is the responsibility of the implantation centre itself. CONCLUSION: It is recommended to develop a new protocol with the involvement of allied professions to clear patient pathways for an effective treatment strategy. Orv Hetil. 2023; 164(19): 729-738.

Changes in the cochlear and retrocochlear parts of the auditory system in 19-39 and 40-60 years old patients with type 1 diabetes mellitus.

Pathophysiological alterations in the cochlea and functional tests of the auditory pathway support that in diabetes both vasculopathy and neural changes could be present. The aim of our research was to study the differential effect of type 1 diabetes mellitus (T1DM) on two different age groups. Audiological investigation was carried out in 42 patients and 25 controls at the same age groups. Investigation of the conductive and sensorineural part of the hearing system by pure tone audiometry, distortion product otoacoustic emission measurement and acoustically evoked brainstem response registration were evaluated. Among the 19-39-year-old people the incidence of hearing impairment was not different in the diabetes and control groups. Among the 40-60-year-old people hearing impairment was more common in the diabetes group (75%) than in the control group (15,4%). Among patients with type 1 diabetes, the mean threshold values were higher in both age groups at all frequencies although significant difference was in 19-39 years old group: 500-4000Hz right ear, 4000Hz left ear, in 40-60 years old group: 4000-8000 Hz both ears. In the 19-39 years old diabetes group only at 8000 Hertz on the left side was a significant (p<0,05) difference in otoacoustic emissions. In the 40-60 years old diabetes group significantly less otoacoustic emissions at 8000 Hz on the right side (p<0,01) and at 4000-6000-8000 Hertz on the left side, (p<0,05, p<0,01, p<0,05 respectively) was present compared to the control group. According to ABR (auditory brainstem response) latencies and wave morphologies, a possible retrocochlear lesion arose in 15% of the 19-39 years old and 25% of the 40-60 years old diabetes group. According to our results, T1DM affects negatively the cochlear function and the neural part of the hearing system. The alterations are more and more detectable with aging.

[Recognition and complex diagnostics of functional hearing loss]. / A funkcionális halláscsökkenés felismerése és komplex diagnosztikája.

INTRODUCTION: Hearing loss is a sensory impairment that impairs speech understanding, communication and therefore the quality of life. Sometimes the patient's perceived loss of function is exaggerated; subjective and objective test results are inconsistent, the subjectively reported hearing loss is more significant, and in these cases functional hearing loss is considered. OBJECTIVE: Our aim was to collect and retrospectively analyze cases with the diagnosis of functional hearing loss, in order to draw conclusions about the characteristics of functional hearing loss, the signs and conditions that may be of attention and the consideration of appropriate rehabilitation. METHODS: Subjective tests were performed with pure-tone auditory threshold, speech understanding and communication tests, which were compared with the results obtained with objective impedance measurements, stapedial reflex tests, otoacoustic emission measurements, and brainstem evoked response recordings. Imaging studies, psychologist, psychiatrist, neurologist, neurologist and other co-specialists were involved as needed. We excluded cases of deception deliberately intended to obtain financial or other benefits. RESULTS: Between 2007 and 2022, 19 patients were diagnosed with functional hearing loss. The majority (17 cases) were female, the complaints were prevalent at a young age (10-41 years); the average age in the study population was 19.6 years, and the majority of patients (13 cases) were children aged 10-17 years. No organic cause was found in 11 cases, and in the remaining cases no detectable organic abnormality explained the extent of the hearing loss experienced by the patient. The degree of functional hearing loss varied (35-120 dB), with an average of 60,2 dB. CONCLUSION: Recognizing and diagnosing functional hearing loss is very difficult and requires a complex series of tests and professional cooperation. Without recognition, the patient may receive unjustified, even harmful and financially burdensome care, which may lead to the deterioration of his condition. Orv Hetil. 2023; 164(8): 283-292.

Revision Stapedotomies: The Role of Periprosthetic Scar Tissue Formation in the Development of Unsatisfactory Hearing Results after Stapedotomy

Abstract Introduction Revision stapes surgeries are difficult to perform, and their audiological results are inferior to primary surgeries. Objective Our goal was to identify the most common and most influential postoperative reasons that cause persistent air-bone gap (ABG) after the primary surgery. Our focus was concentrated on the mechanical dysfunctions in the middle ear, with special regard to postoperative adhesion formation. Methods We performed a retrospective case series study with 23 cases that underwent revision stapedotomies. Results A significant improvement was seen in ABG and air conduction levels after surgery. The periprosthetic adhesion formation was seen in 65% of the cases, and it was the primary cause behind the unsatisfactory hearing result in 30% of cases. There was no significant difference in the level of persistent ABGs after the primary surgery, in case of the intratympanic adhesion presence, compared with the presence of other surgical failures. Concerning hearing and ABG gain after revision surgery, the non-inferiority of the negative effect associated with adhesion was shown compared with the other reasons. Conclusion The revision stapedotomy is an efficient treatment option in case of persistent ABG. Periprosthetic adhesions are the most common intratympanic reasons for compromised audiological outcomes after stapedotomy.

Revision Stapedotomies: The Role of Periprosthetic Scar Tissue Formation in the Development of Unsatisfactory Hearing Results after Stapedotomy.

Introduction Revision stapes surgeries are difficult to perform, and their audiological results are inferior to primary surgeries. Objective Our goal was to identify the most common and most influential postoperative reasons that cause persistent air-bone gap (ABG) after the primary surgery. Our focus was concentrated on the mechanical dysfunctions in the middle ear, with special regard to postoperative adhesion formation. Methods We performed a retrospective case series study with 23 cases that underwent revision stapedotomies. Results A significant improvement was seen in ABG and air conduction levels after surgery. The periprosthetic adhesion formation was seen in 65% of the cases, and it was the primary cause behind the unsatisfactory hearing result in 30% of cases. There was no significant difference in the level of persistent ABGs after the primary surgery, in case of the intratympanic adhesion presence, compared with the presence of other surgical failures. Concerning hearing and ABG gain after revision surgery, the non-inferiority of the negative effect associated with adhesion was shown compared with the other reasons. Conclusion The revision stapedotomy is an efficient treatment option in case of persistent ABG. Periprosthetic adhesions are the most common intratympanic reasons for compromised audiological outcomes after stapedotomy. Adhesion formations have the same negative effect on ABG development as any other surgical failure, and the revision could be more challenging in these cases. These findings highlight the use of the most atraumatic surgical technique and preservation of intact intratympanic mucosa during middle ear surgery.

Early postoperative gustatory dysfunction after middle ear surgery / Korai posztoperatív ízérzészavar középfülsebészeti beavatkozásokat követoen

Introduction: Preserving maximal quality of life is an important factor in middle ear surgery according to current standards. Taste disturbance is a common postoperative complication, which can be explained with the risk of injury due to the localisation of chorda tympani. The knowledge about this complication is mandatory for optimal surgical decision-making and for patient education as well. Objective: Investigation of early postoperative taste disturbances, to clarify the differences between the impact of different surgical interventions, and the impact of nerve manipulation. Methods: 15 stapes surgeries and 28 tympanoplasties were investigated. Patients answered subjective questionnaires before surgery and on the first postoperative day. Visual analogue scale (VAS) was used to measure the degree of disturbances (0-10). Degree of nerve manipulation was classified into 5 groups. Results: No significant differences between the impact of stapes surgeries and tympanoplasties could be found (9, 9.1; p = 0.861). In groups '0', '1' and '2', the VAS scores were 10, 9.26, and 8.5. Between the groups no manipulation (0) and significant manipulation without macroscopic injury (2), the difference was significant (10, 8.5; p = 0.039). In the stapes surgery group, no severe taste disturbance (VAS<5) was found. Discussion: In the case of adequate microscopic surgical technique, the rate of postoperative taste disturbances is relatively low. Conclusions: The rate of postoperative taste disturbance could be kept at a low level while the continuity of the chorda tympani could be preserved in the majority of cases. The postoperative morbidity rate is primarily influenced by the degree of nerve manipulation and not by the type of surgery.

Universal newborn hearing screening with automated auditory brainstem response (AABR) in Hungary: 5-year experience in diagnostics and influence on the early intervention.

PURPOSE: In 2015 a new regulation and guidelines for the universal newborn hearing screening by AABR measurement have been implemented in Hungary. The aim of our study was to analyse (1) the past 5 years of data from our diagnostic centre about the incidence and types of congenital hearing losses, and (2) the first experiences with the National Newborn Hearing Screening Registry, started in 2019, and (3) the influence of the screening on the pediatric cochlear implant program. METHODS: 1269 children referred to our diagnostic centre between 2017 and 2021 were investigated. A third AABR measurement and full audiological evaluation were performed. Furthermore, one-year period data of the screening registry, and the number of implanted children at or under the age of 3 were analysed using the national databases. RESULTS: Altogether 276 newborns (22% of the referred cases after the two-stage screening) had hearing loss, 134 (49%) out of them was conductive origin, almost twice frequent in male as in female. Permanent sensorineural hearing impairment was found in 142 (51%), 58 (40%) of them had bilateral, severe to profound hearing loss, occurring more frequently in male as in female. The national digital registration of the screening data within 12 months concerned 68%. The number of early cochlear implantation in one year increased from 1 to 23 children in the past 15 years. CONCLUSION: A third AABR after the two-stage screening increased the efficiency and filtered the 78% false-positive cases. The audiological diagnostics verified and typed the hearing losses ensuring the early intervention.

Comparative Study Between the Auditory and Vestibular Functions in Ménière's Disease.

OBJECTIVES: To evaluate the relationship between the loss of the cochleovestibular functions in Ménière's disease (MD). METHODS: Forty-three patients with definite MD underwent pure-tone audiometry (PTA) and caloric test. Canal paresis (CP%), dPTA (interaural difference), and average PTA results were contrasted. IBM SPSS V24 was used for statistical analysis. RESULTS: According to PTA, most patients were in stage C, and caloric weakness was found in 29 patients. Linear (R2 = 0.06) and nonlinear correlation tests (rho = 0.245, P = .113) between canal paresis (CP%) and dPTA showed no correlation, as well as between CP% and PTA analysis (R2 = 0.007, rho = 0.11, P = .481). As per the categorial analysis, no correlation was detected between the groups either (κ = 0.174, 95% CI: 0.0883 - 0.431). Based on the results of the analysis, it was concluded that a more advanced stage determined by audiometry does not indicate increasing values in the CP% parameter. CONCLUSIONS: Audiometric changes do not directly correspond with the vestibular ones; therefore, no specific correlation exists between them. Thus, for therapy planning and diagnosis, both tests are necessary.

Chronic Oral Selegiline Treatment Mitigates Age-Related Hearing Loss in BALB/c Mice.

Age-related hearing loss (ARHL), a sensorineural hearing loss of multifactorial origin, increases its prevalence in aging societies. Besides hearing aids and cochlear implants, there is no FDA approved efficient pharmacotherapy to either cure or prevent ARHL. We hypothesized that selegiline, an antiparkinsonian drug, could be a promising candidate for the treatment due to its complex neuroprotective, antioxidant, antiapoptotic, and dopaminergic neurotransmission enhancing effects. We monitored by repeated Auditory Brainstem Response (ABR) measurements the effect of chronic per os selegiline administration on the hearing function in BALB/c and DBA/2J mice, which strains exhibit moderate and rapid progressive high frequency hearing loss, respectively. The treatments were started at 1 month of age and lasted until almost a year and 5 months of age, respectively. In BALB/c mice, 4 mg/kg selegiline significantly mitigated the progression of ARHL at higher frequencies. Used in a wide dose range (0.15-45 mg/kg), selegiline had no effect in DBA/2J mice. Our results suggest that selegiline can partially preserve the hearing in certain forms of ARHL by alleviating its development. It might also be otoprotective in other mammals or humans.

Anti-PD-1 Therapy Does Not Influence Hearing Ability in the Most Sensitive Frequency Range, but Mitigates Outer Hair Cell Loss in the Basal Cochlear Region.

The administration of immune checkpoint inhibitors (ICIs) often leads to immune-related adverse events. However, their effect on auditory function is largely unexplored. Thorough preclinical studies have not been published yet, only sporadic cases and pharmacovigilance reports suggest their significance. Here we investigated the effect of anti-PD-1 antibody treatment (4 weeks, intraperitoneally, 200 µg/mouse, 3 times/week) on hearing function and cochlear morphology in C57BL/6J mice. ICI treatment did not influence the hearing thresholds in click or tone burst stimuli at 4-32 kHz frequencies measured by auditory brainstem response. The number and morphology of spiral ganglion neurons were unaltered in all cochlear turns. The apical-middle turns (<32 kHz) showed preservation of the inner and outer hair cells (OHCs), whilst ICI treatment mitigated the age-related loss of OHCs in the basal turn (>32 kHz). The number of Iba1-positive macrophages has also increased moderately in this high frequency region. We conclude that a 4-week long ICI treatment does not affect functional and morphological integrity of the inner ear in the most relevant hearing range (4-32 kHz; apical-middle turns), but a noticeable preservation of OHCs and an increase in macrophage activity appeared in the >32 kHz basal part of the cochlea.

Intratympanic gentamycine for Ménière's disease: is there a selective vestibulotoxic effect?

PURPOSE: The aim of our study is to investigate the effectiveness and safety of the treatment, based on vertigo diaries and pure tone audiograms. METHODS: The complete medical documentation of 105 definite patients suffering from Ménière's disease was analyzed. In the studied group, nine patients were treated with intratympanic gentamycine. Long-term follow-up of the patients was carried out, using vertigo diaries, medical letters, anamnestic data, and pure tone audiograms. Audiometric results and vertigo complaints before and after treatment were contrasted using IBM SPSS V24 software. RESULTS: Based on our analysis, vertigo attacks appeared significantly less often after gentamycine treatment [p < 0.001; Odds ratio 0.003 (95% CI 0.001-0.012)], which confirms the efficacy of the therapy. Pure tone stages before and after the application of gentamycine were contrasted using the Mann-Whitney U test. When comparing the audiometric results of long-term follow-ups by using the logistic regression, a statistically significant difference was observed between the treated and not treated groups [p = 0.001; Odds ratio 0.141 (95% CI 0.064-0.313)], and based on the survivorship curve hearing impairment was more common in the not treated group which also supports our results. Based on the non-parametric test, there was no significant difference (p = 0.84) between the pure-tone stages of the control group and of those treated with gentamycine. CONCLUSION: Our results indicate that intratympanic gentamycine is effective in controlling vertigo attacks, and there is no higher risk for hearing loss than in case of spontaneous progression of the disorder.

[Verification results of objective newborn hearing screening]. / Az újszülöttkori objektív hallásszurés utánvizsgálatának eredményei.

Sufficient hearing is the cornerstone of the development of children's complex sensory perception, sound recognition, speech development and optimal communication skills. Hearing screening of newborns is necessary to detect congenital hearing disorders. Compulsory objective hearing screening in Hungary is a significant improvement in early diagnosis. The Audiological Department of Otorhinolaryngology, Head and Neck Surgery Clinic at Semmelweis University serves as a verification center for children identified via the compulsory objective newborn hearing screening and necessitates more detailed assessment. The goal of this study was to summarize the verification results of the year 2018. Case history, ENT examination, electric response measurement, impedance tests, otoacoustic emission measurement, surdopedagogical examination, and genetic examination are the basics of the diagnosis and the therapy as well. Altogether 261 newborns were examined in 2018 and 164 were subjected to audiological tests during the analyzed seven-month period. Normal hearing was detected in both ears in 77% of the cases, while hearing loss has been verified in 37 patients (23% of cases). Permanent hearing loss has been diagnosed in 19 cases, 4 unilateral and 15 bilateral. Hearing loss of sensorineural origin was confirmed in 17, conductive in 2 children. Temporary hearing loss caused by otitis media with effusion was found in further 18 children which healed spontaneously in most cases. Organized neonatal objective hearing examination has been established in Hungary in 2015. As a result, we can diagnose and provide care for children with hearing loss at the earliest stage. The National Newborn Hearing Screening Registry ensures a well-coordinated and smooth process. Orv Hetil. 2019; 160(47): 1850-1855.

[Etiological factors of sensorineural hearing loss in children after cochlear implantation]. / Halláscsökkenést okozó etiológiai tényezok cochlearis implantáción átesett gyermekekben.

Introduction: Congenital sensorineural hearing loss is one of the most common sensory defects affecting 1-3 children per 1000 newborns. There are a lot of causes which result in congenital hearing loss, the most common is the genetic origin, but infection, cochlear malformation or other acquired causes can be reasons as well. Aim: The aim of this study was to establish the etiological factors of congenital profound sensorineural hearing loss in children who underwent cochlear implantation. Results: Our results show that the origin of the hearing loss was discovered in 62.9% of our patients. The most common etiological factor was the c.35delG mutation of the gap junction protein ß-2 gene, the allele frequency was 38.7% in our cohort. Infection constituted to 10.1%, and meningitis and cytomegalovirus infection were the second most common cause. 79.9% of our patients received sufficient hearing rehabilitation before the end of the speech development's period (6 years old), but 11.2% of our cases were still diagnosed late. Conclusions: Based on our data we can state that genetic evaluation is crucial in the diagnostic process of congenital profound sensorineural hearing loss. Sufficient hearing rehabilitation affects the whole life of the child, and by late cochlear implantation the speech development falls behind. We can decrease the ratio of the late implantation with the new protocol of newborn hearing screening, and with sufficient information provided to the colleagues, so the children may be referred to the proper center for rehabilitation without delay. Orv Hetil. 2019; 160(21): 822-828.

Cochlear implantation under local anesthesia: a possible alternative for elderly patients.

INTRODUCTION: As average life-expectancy increases, a sufficient hearing rehabilitation for elderly patients with severe-to-profound sensorineural hearing loss becomes more important. Cochlear implantation is a relatively safe surgical procedure also for elderly patients, the higher risk is caused by general anesthesia. We report on four patients who underwent cochlear implantation under local anesthesia. METHODS: After detailed preoperative examinations (audiological tests, imaging, genetic tests, evaluation of motivation and compliance of the patient), four patient with severe-to-profound hearing loss were selected for cochlear implantation under local anesthesia. For the electrode insertion, we used the posterior suprameatal approach technique. Pre- and postoperative pure tone audiometry and speech-perception tests were conducted to prove the success of the procedure. RESULTS: The mentioned technique was applied; the average length of the operation was 52 min. The intraoperative measurements showed normal impedance and normal neuronal response telemetry, all the patients had sound experience during the intraoperative examination of the engineer. No complications were observed. The postoperative audiological tests showed a significant increase in the hearing perception. CONCLUSION: Cochlear implantation under local anesthesia is a safe and fast procedure for elderly patients. The intraoperative sound experience can give an extra motivation in the postoperative rehabilitation. Our results prove that by carefully selected elderly patients cochlear implantation can assure a significant increase in speech perception. We can establish that the new posterior suprameatal approach technique combined with local anesthesia presents a viable future option for those patients who were inoperable beforehand because of high risks of general anesthesia.

Analysis of GJB2 mutations and the clinical manifestation in a large Hungarian cohort.

PURPOSE: Pathogenic variants of the gap junction beta 2 (GJB2) gene are responsible for about 50% of hereditary non-syndromic sensorineural hearing loss (NSHL). In this study, we report mutation frequency and phenotype comparison of different GJB2 gene alterations in Hungarian NSHL patients. METHODS: The total coding region of the GJB2 gene was analyzed with Sanger or NGS sequencing for 239 patients with NSHL and 160 controls. RESULTS: Homozygous and compound heterozygous GJB2 mutations were associated with early onset serious clinical phenotype in 28 patients. In 24 patients, two deletion or nonsense mutations were detected in individuals with mainly prelingual NSHL. In compound heterozygous cases, a combination of deletion and missense mutations associated with milder postlingual NSHL. A further 25 cases harbored single heterozygous GJB2 mutations mainly associated with later onset, milder clinical phenotype. The most common mutation was the c.35delG deletion, with 12.6% allele frequency. The hearing loss was more severe in the prelingual groups. CONCLUSION: The mutation frequency of GJB2 in the investigated cohort is lower than in other European cohorts. The most serious cases were associated with homozygous and compound heterozygous mutations. In our cohort the hearing impairment and age of onset was not altered between in cases with only one heterozygous GJB2 mutation and wild type genotype, which may exclude the possibility of autosomal dominant inheritance. In early onset, severe to profound hearing loss cases, if the GJB2 analysis results in only one heterozygous alteration further next generation sequencing is highly recommended.

[ACOUSTIC CR®-NEUROMODULATION -- FIRST EXPERIENCIES IN HUNGARY WITH A NOVEL METHOD IN THE THERAPY OF CHRONIC SUBJECTIVE TINNITUS]. / AKUSZTIKUS CR®-NEUROMODULÁCIÓ -- EGY ÚJ KEZELÉSI ELJÁRÁS MAGYARORSZÁGI BEVEZETÉSE SORÁN SZERZETT ELSO TAPASZTALATOK KRÓNIKUS SZUBJEKTIV FÜLZÚGÁSBAN SZENVEDO BETEGEKNÉL.

OBJECTIVE: Acoustic CR®-neuromodulation is a novel patented method for the therapy of chronic subjective tinnitus and has been tested in Hungary, as one of the first European countries introducing this procedure. It can be used for the treatment of monaural or binaural tonal tinnitus. Suitability of patients for this therapy was assessed by the help of an appropriate set of criteria. Aim of our study was to analyze 6-month therapy and related measurement data of patients first treated with this method in Hungary and evaluate the results. METHOD: 27 outpatients (20 males, seven females) with a minimum of 6-month long history of subjective tinnitus were assessed (four detected on the right side, six on the left side, 17 on both sides) who were treated for six months by Acoustic CR®-neuromodulation. On 44 treated ears (21 right, 23 left), changes of tinnitus frequency and loudness were measured and analysed, using Visual Analogue Scale (VAS) loudness/annoyance/pitch scores and Tinnitus Handicap Inventory tests, which were performed at defined intervals during the treatment period. RESULTS: During this 6-month treatment period, significant decrease was detected in tinnitus frequency and loudness by tinnitometry (irrespective of the affected side), and an improvement in VAS annoyance/pitch scores and THI test results. VAS loudness did not show any significant changes. CONCLUSION: Acoustic CR®-neuromodulation therapy may be a useful treatment of subjective chronic tinnitus, but its efficacy should be proved in controlled clinical trials.

Simultaneous measurement of glutamate and dopamine release from isolated guinea pig cochlea.

Glutamate is proved to be a neurotransmitter in the mammalian cochlea, transmitting signals between the inner hair cells and the afferent cochlear nerve terminals. The transmission in this synapse is modulated by the lateral olivocochlear efferent fibers by releasing dopamine and other neurotransmitters. This study undertakes to measure simultaneously the release of dopamine and glutamate from isolated guinea pig cochleae. We combined the in vitro microvolume superfusion method, that uses liquid scintillation analysis, to measure [3H]dopamine with high pressure liquid chromatography (HPLC) to determine the glutamate content of the superfusate at rest and during stimulation. The release of both neurotransmitters was significantly increased when electrical field stimulation was applied at a 10 Hz rate. The nonselective sodium-channel inhibitor tetrodotoxin (TTX) at 1 microM completely blocked the effect of stimulation, indicating the neural origin of both dopamine and glutamate. The dopamine receptor antagonist sulpiride at 100 microM and the dopamine receptor agonist bromocriptine at 20 microM did not change the release of glutamate. In contrast, both bromocriptine and sulpiride significantly increased the stimulation-evoked release of dopamine. The effect of sulpiride is most likely due to the blockade of dopamine autoreceptor. Possible explanations why bromocriptine increased the release include: (1) its partional agonist activity; (2) desensitizations of dopamine autoreceptors; or (3) the higher D1 receptor activity of bromocriptine than sulpiride. This study could provide further insights about the role of dopamine and glutamate in cochlear neurotransmission.