Improvement In Auditory Function Research Articles

Efficiency of gene therapy for sensorineural hearing loss in mouse model: A meta-analysis.

Sensorineural hearing loss (SNHL) is a disorder characterized by the loss or impairment of cochlear hair cells or the auditory nerve. In recent years, gene therapy has emerged as a promising approach for SNHL treatment. The objective of this study is to evaluate the impact of gene therapy on the restoration or improvement of auditory function in mouse model with loss or impairment of hearing. Studies with clear experimental designs, and auditory brainstem response (ABR) analysis as relevant outcome measures were included by searching PubMed, Scopus, and Web of Science databases. The PRISMA guideline was used for abstracting data and assessing data quality and validity. A quantitative synthesis was performed using a random effects model to examine the effect of gene therapy on auditory function in SNHL. Nine articles including 71 studies meeting the inclusion criteria were identified. These studies explored therapies targeting the TMC1, VGLUT3, USH1C, CLRN1, WHRN, and PJVK genes, with genetic material ranging from 1.8 × 1011 and 1.4 × 1014 gc/mL being delivered to the inner ear through round window membrane, cochleostomy, or posterior semicircular canal injection methods. The hearing test results showed a significant mean difference of 26.91 dB (95% CI: 22.01-31.85) in favor of the experimental group. Although promising results have been obtained regarding the potential success of gene therapy in SNHL, further investigation is needed to explore the long-term effects of gene therapy, treatment response rates, and the relationships between different genetic mutation types.

Guiding Ethical Decisions in Cochlear Implantation for the Hearing Impaired with Comorbid Psychosis.

AbstractCochlear implants can restore hearing in people with severe hearing loss and have a significant impact on communication, social integration, self-esteem, and quality of life. However, whether and how much clinical benefit is derived from cochlear implants varies significantly by patient and is influenced by the etiology and extent of hearing loss, medical comorbidities, and preexisting behavioral and psychosocial issues. In patients with underlying psychosis, concerns have been raised that the introduction of auditory stimuli could trigger hallucinations, worsen existing delusions, or exacerbate erratic behavior. This concern has made psychosis a relative contraindication to cochlear implant surgery. This is problematic because there is a lack of data describing this phenomenon and because the psychosocial benefits derived from improvement in auditory function may be a critical intervention for treating psychosis in some patients. The objective of this report is to provide an ethical framework for guiding clinical decision-making on cochlear implant surgery in the hearing impaired with psychosis.

A Randomised Controlled Trial on the Effect of Hamulectomy on Hearing Outcomes in Cleft Palate Patients - A Comparative Study.

Cleft palate, a common congenital craniofacial defect, requires surgical repair and many surgical approaches have been employed for the same to reduce the risk of post-operative complications and improve outcomes. In order to achieve tension free closure, fracture of pterygoid hamulus has been advised. However, the effect of this manoeuvre on auditory functions remains debatable. The study was designed to evaluate the effect of hamulectomy on auditory function during the post-operative period after palatoplasty. The present study enrolled 100 participants aged 10 months-2 years with isolated cleft palate defect. They were randomly divided into two groups: palatoplasty with hamulectomy (n = 50) and palatoplasty without hamulectomy (n = 50). Hearing outcomes were evaluated using objective measures (otoscopy, tympanometry, and otoacoustic emission [OAE] tests) at 1-month and 6-month post-operative follow-up visits. The Chi-square test was used to analyse the data and significance level was kept at P ≤ 0.05. The findings of otoscopy, tympanometry and OAE tests were statistically similar between the two study groups (P > 0.05; Chi-square test) at both one month and six months follow-up visits. Another noteworthy observation was improvement in auditory function during follow-up period indicating recovery of middle ear function following palatoplasty. The addition of hamulectomy to the palatoplasty treatment may improve the hearing outcomes for cleft palate patients and can be adopted to achieve tension free closure.

Adaptation to Noise in Spectrotemporal Modulation Detection and Word Recognition.

Noise adaptation is the improvement in auditory function as the signal of interest is delayed in the noise. Here, we investigated if noise adaptation occurs in spectral, temporal, and spectrotemporal modulation detection as well as in speech recognition. Eighteen normal-hearing adults participated in the experiments. In the modulation detection tasks, the signal was a 200ms spectrally and/or temporally modulated ripple noise. The spectral modulation rate was two cycles per octave, the temporal modulation rate was 10 Hz, and the spectrotemporal modulations combined these two modulations, which resulted in a downward-moving ripple. A control experiment was performed to determine if the results generalized to upward-moving ripples. In the speech recognition task, the signal consisted of disyllabic words unprocessed or vocoded to maintain only envelope cues. Modulation detection thresholds at 0 dB signal-to-noise ratio and speech reception thresholds were measured in quiet and in white noise (at 60 dB SPL) for noise-signal onset delays of 50 ms (early condition) and 800 ms (late condition). Adaptation was calculated as the threshold difference between the early and late conditions. Adaptation in word recognition was statistically significant for vocoded words (2.1 dB) but not for natural words (0.6 dB). Adaptation was found to be statistically significant in spectral (2.1 dB) and temporal (2.2 dB) modulation detection but not in spectrotemporal modulation detection (downward ripple: 0.0 dB, upward ripple: -0.4 dB). Findings suggest that noise adaptation in speech recognition is unrelated to improvements in the encoding of spectrotemporal modulation cues.

The Effects of Music-Based Auditory Training on Hearing-Impaired Older Adults With Mild Cognitive Impairment.

The present study aimed to determine the effect of music-based auditory training on older adults with hearing loss and decreased cognitive ability, which are common conditions in the older population. In total, 20 older adults diagnosed with both mild-to-moderately severe hearing loss and mild cognitive impairment (MCI) participated. Half of this group were randomly assigned to the auditory training group (ATG), and the other half were designated as the control group (CG). For the ATG, a 40-minute training session (10 minutes for singing a song, 15 minutes for playing instruments, and 15 minutes for playing games with music discrimination) was conducted twice a week for 8 weeks (for a total of 16 sessions). To confirm the training effects, all participants were given tests pre- and post-training, and then a follow-up test was administered 2 weeks after the training, using various auditory and cognitive tests and a self-reporting questionnaire. The ATG demonstrated significant improvement in all auditory test scores compared to the CG. Additionally, there was a notable enhancement in cognitive test scores post-training, except for the digit span tests. However, there was no statistically significant difference in the questionnaire scores between the two groups, although the ATG did score higher post-training. The music-based auditory training resulted in a significant improvement in auditory function and a partial enhancement in cognitive ability among elderly patients with hearing loss and MCI. We anticipate that this music-based approach will be adopted for auditory training in clinical settings due to its engaging and easy-to-follow nature.

Reversal of an existing hearing loss by gene activation in Spns2 mutant mice

Hearing loss is highly heterogeneous, but one common form involves a failure to maintain the local ionic environment of the sensory hair cells reflected in a reduced endocochlear potential. We used a genetic approach to ask whether this type of pathology can be reversed, using the Spns2tm1a mouse mutant known to show this defect. By activating Spns2 gene transcription at different ages after the onset of hearing loss, we found that an existing auditory impairment can be reversed to give close to normal thresholds for an auditory brainstem response (ABR), at least at low to mid stimulus frequencies. Delaying the activation of Spns2 led to less effective recovery of ABR thresholds, suggesting that there is a critical period for intervention. Early activation of Spns2 not only led to improvement in auditory function but also to protection of sensory hair cells from secondary degeneration. The genetic approach we have used to establish that this type of hearing loss is in principle reversible could be extended to many other diseases using available mouse resources.

Acromegaly in the differential diagnosis of hearing loss

Acromegaly is a multifactorial neuroendocrine disease caused by hyperproduction of growth hormone (GH). In more than 95% of cases the reason of acromegaly the GH-secreting pituitary adenoma. In patients with this neuroendocrine disease, a slowly developing complex of symptom can manifest with concomitant pathological conditions, including auditory function disordersDiagnostic difficulties of acromegaly at the ambulatory stage determine the importance of doctor`s awareness in different medical specialties.Here we demonstrate a clinical case of the improvement of the auditory function due to combined surgical and medical treatment of a patient with the pituitary macroadenoma, acromegaly and hearing loss.Anamnesis features: a patient with an active stage of acromegaly and a pituitary macroadenoma measuring 57x35x32 mm with ante-, supra-, infra-, parasellar spread, (Knosp III(D), Knosp IV(S) noted a violation of auditory function. She was consulted by an otolaryngologist, sensorineural hearing loss on the right of the 3rd degree was diagnosed, on the left of the 1st degree. The patient underwent surgical treatment of pituitary adenoma, noted a significant improvement in auditory function in the early postoperative period. Six months later, repeated audiometry was performed, marked regression of hearing damage was noted.The case described by us indicates the reversibility of a rare complication of acromegaly - hearing loss and the importance of an interdisciplinary approach in the management of patients with this pathology.

The most informative otoacoustic emission indicators for prognostication the course and solving expert issues in the participants of the joint forces operation with combat acutrauma

Introduction: Registration of otoacoustic emission is the general objective method in diagnostics of receptor defeats of the auditory system, first of all the organ of Corti outer hair cells. At an acutrauma the receptive field of auditory system suffers. The purpose: to determine the possible prognostic criteria of progression of perceptual hearing disorders according to distortion-product otoacoustic emission (DPOAE) in servicemen who received acutrauma in real combat conditions. Material and methods: In the this work indicators for distortion-product otoacoustic emission (DPOAE) in servicemen who received acutrauma in the area of the joint forces operation have been investigated. We had examined 2 groups of people: 1st group – 30 persons who had shown improvement in auditory function and general condition after treatment, 2nd group – 30 persons in whom disease progression had observed, they had no positive dynamics after treatment. The investigation of otoacoustic emission (OAE) was conducted by analyzing system “Eclipse” of the “Interacoustics” Company (Denmark). Was used the generally accepted methodology. The recording has performed in the frequency band (1 - 6) kHz. Results. The complete adequate response of OAE across the entire frequency spectrum has been registered in only one patient with combat acutrauma from group 1. In most of the surveyed patients in whom the OAE was registered, a partially positive test was obtained as already mentioned. The response was considered as registered when the signal-to-noise ratio exceeded or was equal to 3 dB. The decision on a partially positive test was made when only one or more of the tested frequency bands had an adequate response. A positive response was registered in 42.6% of fighters of group 1 and 31.25% of group 2. According to our data, in patients of group 1 in 57.4% of cases the DPOAE was not registered at any of the frequencies, the same situation in patients of group 2 were in 68.75%. Thus in group 1 positive, including in part, the DPOAE was recorded at one frequency in 16.7% of cases, at twо frequencies - at 18.5%, at three frequencies - 7.4% and at four frequencies -1 . 8%. In group 2, a positive test was registered at one frequency in 16.7% of cases, at twо frequencies - 4.2% at three frequencies - 6.2%. At four frequencies, a positive test (complete response) was not registered in any patient of group 2. We analyzed at which frequencies the response was most often recorded with partially positive DPOAE results in surveyed patients. The corresponding percentages were calculated from the total number of received responses. At the same time, in patients of group 1 partial response of DPOAE have been registered more often than in group 2. In group 1, DPOAE was recorded at frequencies of 1 kHz in 52.2% of cases, 2 kHz - 34.8%, 4 kHz - 78.3%, 6 kHz - 21.7%. In persons from group 2, with a progressive course of sensorineural hearing loss, the DPOAE response was observed at frequencies of 1 kHz - 38.5%, 2 kHz - 46.1%, 4 kHz - 53.8%, 6 kHz - 23.1%. Thus, in both groups, the DPOAE response have been most often recorded at 4 kHz: (78.3%) and (53.8%), respectively. It is followed by the frequency of registration in 1 group with a frequency of 1 kHz (52.2%), and in group 2 with 2 kHz (46.1%). Thus, registration of the DPOAE will promote objectification of sensorineural hearing loss course at a combat acutrauma. Conclusions: The conducted researches have shown the importance of DPOAE definition at patients with a combat acutrauma that promotes timely and objective detection of receptor structures defeats of the auditory system at such patients. The results of DPOAE registration can be used to predict the course of sensorineural hearing loss and assess adverse factors in combat acutrauma. Complete absence of registration of DPOAE at servicemen with a combat acutrauma can serve as an objective sign of prognostically unfavorable course of sensorineural hearing loss at such patients.

Single-stage open tympanoplasty in the form of tympanosclerosis with fixation of the stapes

We used several variants of one-stage tympanoplasty, including our own method, according to which, in the absence of an anvil and malleus after mobilisation of the stapes, ossiculoplasty with partial or complete ossicular prosthesis and myringoplasty simultaneously preventively created a support (neo-malleus) in the thickness of the neotympanic membrane. To assess the effectiveness of different variants of single-stage tympanoplasty, the long-term functional results were compared in terms of 6 to 12 months after the intervention with preoperative indicators. Standard methods of statistical estimation with calculation of descriptive statistics and methods of statistical hypothesis testing based on nonparametric Wilcoxon criterion for related samples were used. All the variants of one-stage tympanoplasty used in the fixation of the stapes are effective and, in general, make it possible to achieve an improvement in auditory function. In the present study, this result was achieved in 61 of 86 patients with tympanosclerosis (71% (65%; 74%) of 95% CI). The functional results of tympanoplasty according to the developed method do not differ from the results of traditional variants with the use of prostheses, but the implementation of this variant of tympanoplasty in the absence of an anvil and hammer allows for the fixation of the stapes during the reoperative stapedotomy using a prosthesis of the piston type without additional surgical stage of the formation of the neomaleus.

The Antioxidant Effect of Rosmarinic Acid by Different Delivery Routes in the Animal Model of Noise-Induced Hearing Loss.

Trans-tympanic Rosmarinic Acid (RA), as compared with the systemic administration, protects against noise-induced auditory hair cell and hearing losses in rats in vivo. ROS production, lipoperoxidative damage, and an imbalance of antioxidant defences play a significant role in noise-induced hearing loss. Several molecules with antioxidant properties have been tested to restore redox homeostasis; however, drug delivery system represents a challenge for their effectiveness. In our model, acute and intense noise exposure induces hearing loss, hair cell death, and oxidative stress, with an increase in superoxide production and over-expression of lipid peroxidation in cochlear structures. RA was administrated in male Wistar rats by trans-tympanic (20 μl) and systemic (10 mg/kg) modality. In systemic administration, RA was injected 1 hour before noise exposure and once daily for the following 3 days. ABRs were measured before and at days 1, 3, 7, and 30 after noise exposure. Rhodamine-phalloidin staining, dihydroethidium and 8-isoprostane immunostainings were performed to assess and quantify outer hair cells loss, superoxide production, and lipid peroxidation in the different experimental groups. Systemic RA administration significantly decreased noise-induced hearing loss and the improvement of auditory function was paralleled by a significant reduction in cochlear oxidative stress. The trans-tympanic modality of drug administration showed a similar degree of protection both at the functional and morphological levels. The effectiveness of RA given via trans-tympanic injection could be interesting for the future application of this minimally-invasive procedure in the treatment of ROS-induced hearing loss.

Predicting the degree of hearing loss in ear-surgery in chronic otitis media

The article provides a comprehensive method for predicting the degree of hearing loss in reconstructive and sanitizing otosurgery in patients with chronic otitis media using scoring system criteria, determining the degree of hearing loss: 1 point is given in case of absence or minor manifestation of the criterion, 2 points – for moderately severe criterion manifestation, 3 points – for significantly expressed criterion manifestation. The total score less or equal to 25 is evaluated as a favorable prognosis for preservation or improvement of auditory function in reconstructive and sanitizing otosurgery, and the total score above 25 points is evaluated as unfavorable prognosis, indicating socially significant hearing loss in the postoperative period of otosurgery in patients with chronic otitis media. The method for predicting the hearing loss degree is implemented before the planned otosurgery in a patient with chronic otitis media in both outpatient and inpatient conditions.

Efficacy of different routes of administration for Coenzyme Q10 formulation in noise-induced hearing loss: Systemic versus transtympanic modality

Conclusion: The effectiveness of a coenzyme Q10 formulation, Q-ter, given via transtympanic injection is interesting for the future application of this minimally invasive procedure in the treatment of reactive oxygen species (ROS)-induced hearing loss. Objective: We focused on antioxidant therapy in noise-induced hearing loss (NIHL). Our study was designed to evaluate the effectiveness of Q-ter for different schedules of drug administration to establish the best modality for treatment. Methods: Rats were exposed to acoustic trauma (10 kHz at 120 dB for 60 min) and received Q-ter according to two modalities: systemic (Q-ter 100 mg/kg for 4 days 1 h before and 3 days post noise exposure) and transtympanic (Q-ter 20 and 40% concentration 1 h before noise exposure). Auditory brainstem response (ABR), immunohistochemical and morphological studies were performed. Results: Q-ter administration significantly decreased NIHL at day 21 from noise exposure. The improvement of auditory function by Q-ter was paralleled by a significant reduction in oxidative stress. The transtympanic and systemic routes of drug administration showed a similar degree of protection.

Improvement in neonatal hearing loss following treatment with thyroxin

AimConsideration of how treatment for hypothyroidism may lead to an improvement in hearing, illustrated by two cases of hearing loss identified by neonatal screening.MethodTwo babies referred for Audiological assessment and...

Therapeutic window for ferulic acid protection against noise-induced hearing loss in the guinea pig

Conclusion: Our results are in agreement with the general idea that natural antioxidants achieve their best cytoprotective capacity if given before and soon after the stressor. Objective: We focused on ferulic acid (FA, 4-hydroxy 3-methoxycinnamic acid), a phenolic compound that is known to exhibit antioxidant properties. Our study was designed to evaluate the effectiveness of FA for different schedules of treatment to establish the ‘therapeutic window’ for FA protection. Methods: Guinea pigs were exposed to acoustic trauma (6 kHz at 120 dB for 60 min) and received a total dose of 600 mg/kg of FA. Group I, noise control; group II, noise + FA (150 mg/kg) for 4 days starting 24 h post exposure; group III, noise + FA (60 mg/kg) 1 h before and 9 days post exposure; group IV, noise + FA (60 mg/kg) given 3 days before and 7 days post exposure; group V, noise + FA (150 mg/kg) 1 h before and 3 days post noise exposure. Auditory brainstem response (ABR) test and immunohistochemical and morphological studies were performed. Results: Group V had significantly decreased noise-induced hearing loss at day 21 from noise exposure. The improvement of auditory function by FA was paralleled by a significant reduction in oxidative stress marker. The other schedules of drug administration showed a minor degree of protection.

Sodium enoxaparin and venovenous hemofiltration for treatment of SNHL

Objectives: Immune-mediated sensorineural hearing loss (IMSNHL) can be caused by immune-mediated disorders localized to the inner ear or secondary to systemic immune diseases: positive test results and beneficial response to therapy support a presumptive diagnosis of immune inner ear disease. Treatment include corticosteroids, cytotoxics agents, and plasmapheresis. These drugs can be effective in reversing such hearing loss, although at the cost of side-effects. Prompted by such observations, we implemented a protocol using sodium enoxaparin associated with a venovenous hemofiltration for treatment of IMSNHL. Methods: Hemofiltration was performed at the first and last day of the protocol while, to begin since the second day of the protocol, sodium enoxaparin was administered subcutaneously at a dose of 4000 IU once a day for 10 days. Every day all patients underwent: liminar tonal audiometry; otoacoustic emission; otoacoustic products of distortion. Blood tests where performed at the beginning, after the fist day, and at the end of the treatment. Specifically excluded were patients with abnormal known coagulation. Results: On discharge, the 89% of patients treated showed an improvement in auditory function. No patient experienced side effects from this treatment. Conclusions: The venovenous hemofiltration selectively eliminates dangerous macromolecules from the blood plasma: the reduction of these macromolecules improves the hemorheological situation. Sodium enoxaparin exerts its effects on capillary blood viscosity, erythrocyte deformability, thrombocyte aggregation, and antiphospholipid antibody activity. The drug shows an anti-inflammatory action in subcutaneus administration. This study suggests further studies but this kind of therapy appears to give encouraging results in the treatment and diagnosis of IMSNHL.

Management of far advanced otosclerosis in the era of cochlear implantation.

To evaluate issues pertaining to cochlear implantation in patients with far advanced cochlear otosclerosis. Prospective cohort. Tertiary care referral center. Eight adult patients (18 years of age or older) referred for management of profound hearing loss, the cause of which was determined to be otosclerosis. Cochlear implantation with multichannel cochlear implant device. Benefit from cochlear implant as measured by CID sentence scores, incidence and management of facial nerve stimulation, and technical issues pertaining to cochlear implantation in this patient population. All patients demonstrated significant improvement in auditory function as measured by performance on CID sentence scores and ability to engage in telephone conversation. Facial nerve stimulation was present in two of eight patients and was managed with deactivation of the stimulating electrodes. Ossification in the basal turn of the cochlea, detected on preoperative computed tomography, necessitated placement of the electrode into the scala vestibuli in two patients and use of a thinner electrode (Nucleus 24) in a third patient. Patients with profound hearing loss secondary to otosclerosis derive excellent benefits from cochlear implantation. Surgical implantation may be complicated by ossification of the cochlea, which can be detected on preoperative computed tomography. Electrode activation may be complicated by facial nerve stimulation, which can be addressed with programming strategies.

Audiologic evaluation of neonates with severe hyperbilirubinemia using transiently evoked otoacoustic emissions and auditory brainstem responses.

To audiologically clarify the lesion site and to test the reliability of transiently evoked otoacoustic emissions (TEOAEs) in hearing screening of hyperbilirubinemic neonates. Eleven neonates with severe hyperbilirubinemia who had exchange transfusion in the neonatal intensive care unit of an academic hospital over a 3-year period were included in this study. They were tested with auditory brainstem response (ABR) and TEOAEs after exchange transfusion during hospitalization or at an immediate follow-up visit after discharge. Follow-up ABR tests were performed when infants showed significant hearing loss. ABR and TEOAE tests were performed on the 11 neonates with severe hyperbilirubinemia after exchange transfusion. Follow-up ABR tests were carried out in 3-month intervals in the four neonates who showed abnormal or no response on initial ABR. Four neonates showed abnormal or no response and the other seven demonstrated normal response in ABR. All 11 neonates passed TEOAEs. Two neonates showed improvement in auditory function at 3- or 6-month follow-up ABR. The results of this study indicate that the site of lesion in hearing loss caused by hyperbilirubinemia may be at the retrocochlear location while the cochlea remains intact. TEOAEs may have limitations in evaluation of hearing in the neonates with hyperbilirubinemia.

Effects of tibolone on auditory brainstem responses in postmenopausal women—a randomized, double-blind, placebo-controlled trial

Objective: To investigate the influence of tibolone, a synthetic steroid, in modifying auditory brainstem response (ABR) in postmenopausal women. Design: Prospective, randomized, double-blind, placebo-controlled trial. Setting: Outpatient menopausal clinic in a university hospital. Patient(s): Twenty-four healthy postmenopausal women. Intervention(s): Administration of either tibolone or placebo for 12 weeks; evaluation of ABR and hormone levels before and after treatment. Main Outcome Measure(s): Changes in auditory brainstem response latencies. Result(s): Comparison of the ABR latency data from the two treatment groups showed a significant decrease in wave II, III, and V peak latencies in women receiving tibolone. No significant differences in pretreatment and posttreatment circulating hormone concentrations were observed between the tibolone and placebo group. Furthermore, there was no significant increase in hormone levels in either of the groups at 12 weeks. Conclusion(s): Our findings show an improvement in auditory function via brainstem auditory neural pathways sensitive to tibolone in postmenopausal women. Tibolone may offer new therapeutic strategies in otologic disorders.

Induction of an inner-ear-specific autoreactive T-cell line for the diagnostic evaluation of an autoimmune disease of the inner ear.

Different patterns of sensorineural hearing loss with a potential improvement in auditory function following immunosuppressive therapy might be caused by an isolated autoimmune disease of the inner ear. Because of the lack of well-defined detection methods to identify autoimmune processes within the inner ear and the fact that the human inner ear is one of the few organs of the body not amenable to diagnostic biopsy, there has been great interest in developing animal models. Previous studies found evidence that this entity might be cellular mediated. By heterologeous immunization of inbred Lewis rats with inner-ear tissue, an autoreactive inner-ear-specific T-cell line was established. After passive transfer of these cells, a labyrinthitis was induced in recipient animals. The experimental design can serve as an animal model for a cellular-mediated autoimmune disease of the inner ear. Further studies have to split the cochlear proteins and to identify the protein with the strongest autoimmunological potency. After biotechnical production of this protein, a clinical test to diagnose an autoimmune disease of the inner ear in man should be possible.

Improvement in Auditory Function Following Pentazocine Suggests a Role for Dynorphins in Auditory Sensitivity

The pharmacologic specificity of potentially beneficial drug effects on the auditory system were investigated. Changes in auditory sensitivity were evaluated in chinchillas following the infusion of an opioid narcotic. This drug (pentazocine) mimics endogenous opioid peptides (dynorphins), postulated to be chemical neurotransmitters (or neuromodulators) within the mammalian cochlea. In this study, two pentazocine enantiomers were investigated over a range of stimulus intensities. Significant baseline-relative changes in compound action potential (CAP) amplitudes were observed following intravenous administration of the kappa-opioid agonist (-)pentazocine (8 mg/kg). The sigma-receptor drug agonist (+)pentazocine (8 mg/kg) produced no measurable auditory effects. The magnitude of the (-)pentazocine effects were inversely related to stimulus intensity, up to 10 dB above threshold (i.e., 10 dB SL). Consistent with the observed amplitude doubling, auditory sensitivity was also improved an average 5-7 dB sound pressure level (SPL) following the administration of (-)pentazocine, while CAP response latencies and cochlear microphonic (CM) amplitudes remained unchanged. Results indicate stereospecific kappa-receptor mediated actions of pentazocine at the auditory nerve, and suggest an auditory role for neuroactive dynorphin peptides contained within the lateral efferent olivocochlear neurons.