RÉSUMÉ
We report the isolation and initial characterization of a new member of the human nicotinic acetylcholine receptor (nAChR) subunit family, alpha10 (CHRNA10), from both inner-ear neuroepithelium and lymphoid tissue. The cDNA is 1959 nucleotides in length, with a coding region predicting a protein of 451 amino acids that is 90% identical to rat alpha10. The alpha10 gene was localized to chromosome 11p15.5. Human alpha10 was detected in human inner-ear tissue, tonsil, immortalized B-cells, cultured T-cells and peripheral blood lymphocytes using reverse transcriptase-polymerase chain reaction, Northern blot hybridization, and immunohistochemistry. We also detected the expression of the human nAChR alpha9 (CHRNA9) mRNA in these same tissues using RT-PCR and Northern blot hybridization.
Sujet(s)
Chromosomes humains de la paire 11/génétique , Récepteurs nicotiniques/génétique , Séquence d'acides aminés , Animaux , Séquence nucléotidique , Technique de Western , Lignée cellulaire , Clonage moléculaire , Exons/génétique , Humains , Immunohistochimie , Hybridation fluorescente in situ , Introns/génétique , Données de séquences moléculaires , Sous-unités de protéines , ARN messager/analyse , ARN messager/génétique , Cartographie par hybrides de radiation , Rats , Récepteurs nicotiniques/analyse , Récepteurs nicotiniques/composition chimique , Alignement de séquences , Similitude de séquences d'acides aminés , TransfectionRÉSUMÉ
Hair cells of the vertebrate inner ear are subject to efferent control by the release of acetylcholine (ACh) from brainstem neurons. While ACh ultimately causes the hair cell to hyperpolarize through the activation of small conductance Ca(2+)-activated K(+) channels, the initial effect is to open a ligand-gated cation channel that briefly depolarizes the hair cell. The hair cell's ligand-gated cation channel has unusual pharmacology that is well matched to that of the nicotinic subunit alpha9 expressed in Xenopus oocytes. We used sequence-specific amplification to identify the ortholog of alpha9 in the chick's cochlea (basilar papilla). Chick alpha9 is 73% identical to rat alpha9 at the amino acid level. A second transcript was identified that differed by the loss of 132 base pairs coding for 44 amino acids near the putative ligand-binding site. RT-PCR on whole cochlear ducts suggested that this short variant is less abundant than the full length alpha9 mRNA. In situ hybridization revealed alpha9 mRNA in sensory hair cells of the chick cochlea. The pattern of expression was consistent with the efferent innervation pattern. The alpha9 label was strongest in short (outer) hair cells on which large calyciform efferent endings are found. Tall (inner) hair cells receiving little or no efferent innervation had substantially less label. The cochlear ganglion neurons were not labeled, consistent with the absence of axo-dendritic efferent innervation in birds. These findings suggest that alpha9 contributes to the ACh receptor of avian hair cells and supports the generality of this hypothesis among all vertebrates.
Sujet(s)
Poulets , Cochlée/métabolisme , Cellules ciliées auditives/métabolisme , Épissage alternatif , Animaux , Séquence nucléotidique , Clonage moléculaire , Cochlée/cytologie , Cochons d'Inde , Cellules ciliées auditives/cytologie , Hybridation in situ , Données de séquences moléculaires , Neurones efférents/métabolisme , Spécificité d'organe/génétique , ARN messager/biosynthèse , Rats , Récepteurs nicotiniques/biosynthèse , Récepteurs nicotiniques/génétique , RT-PCR , Alignement de séquences , Similitude de séquences d'acides aminésRÉSUMÉ
The efferent cholinergic pathways to the vestibular periphery have yet to be fully characterized. While the nicotinic acetylcholine receptor subunit (nAChR) alpha 9 is now regarded as the principle receptor for efferent cholinergic signaling to the organ of Corti, there is still uncertainty over how the more complex efferent effects of the labyrinth are produced. Recent experimental work has demonstrated that the nAChR alpha 9 is present in the vestibular end-organs of the rat and mouse, suggesting that alpha 9 may be one of the mediators of efferent cholinergic signaling in the vestibular periphery as well. In this experiment, we sought to determine whether alpha 9 was also present in the vestibular end-organs of the chick. A homologue of alpha 9 has been cloned recently from the chick cochlea. Using reverse transcription polymerase chain reaction (RT-PCR), individual vestibular end-organ preparations, including posterior ampulla, combined horizontal and superior ampulla, saccule, utricle, and the vestibular ganglion were screened for alpha 9 messenger RNA expression. In each end-organ and the vestibular ganglion, a cDNA of the expected size was obtained by RT-PCR and was confirmed to be alpha 9 by sequence analysis. Further, alpha 9 mRNA was identified by RT-PCR from individually isolated type I and type II vestibular hair cells (single-cell RT-PCR). Lastly, insitu hybridization using digoxigenin-labeled alpha 9 riboprobes confirmed the presence of alpha 9 in type I and type II hair cells throughout the vestibular periphery. These results demonstrate the expression of alpha 9 in the vestibular end-organs of the chick, and lend further support for the role of alpha 9 as a mediator of efferent cholinergic signaling in vestibular hair cells.
Sujet(s)
Cellules ciliées vestibulaires/composition chimique , Fragments peptidiques/analyse , Récepteurs nicotiniques/composition chimique , Animaux , Poulets , Ganglions/physiologie , Hybridation in situ , Souris , Rats , RT-PCR , Nerf vestibulaire/physiologieRÉSUMÉ
Cochlear frequency selectivity in lower vertebrates arises in part from electrical tuning intrinsic to the sensory hair cells. The resonant frequency is determined largely by the gating kinetics of calcium-activated potassium (BK) channels encoded by the slo gene. Alternative splicing of slo from chick cochlea generated kinetically distinct BK channels. Combination with accessory beta subunits slowed the gating kinetics of alpha splice variants but preserved relative differences between them. In situ hybridization showed that the beta subunit is preferentially expressed by low-frequency (apical) hair cells in the avian cochlea. Interaction of beta with alpha splice variants could provide the kinetic range needed for electrical tuning of cochlear hair cells.
Sujet(s)
Cellules ciliées auditives/physiologie , Ouverture et fermeture des portes des canaux ioniques , Canaux potassiques calcium-dépendants , Canaux potassiques/physiologie , Épissage alternatif , Animaux , Calcium/métabolisme , Lignée cellulaire , Électrophysiologie , Expression des gènes , Humains , Hybridation in situ , Cinétique , Sous-unités bêta des canaux potassiques calcium-dépendants de grande conductance , Canaux potassiques calcium-dépendants de grande conductance , Potentiels de membrane , Techniques de patch-clamp , Canaux potassiques/génétique , Caille , ARN messager/génétique , ARN messager/métabolisme , RT-PCR , TransfectionRÉSUMÉ
There are two tissues in the adult mammalian cochlea that are post-synaptic to cholinergic efferent fibers: The outer hair cells (OHCs) and the dendrites of the afferent fibers of the type I spiral ganglion cells. The unusual nicotinic-like pharmacology of cochlear cholinergic responses and the unique embryonic development of cochlear tissues suggest that the inner-ear nicotinic cholinergic receptor (nAChR) may be different from nAChRs described previously at synapses in the mammalian brain, autonomic ganglia, or skeletal muscle. In this study, we determined the mRNA expression of the alpha2-7, alpha9, and beta2-4 subunits of the nicotinic acetylcholine receptor (nAChR) family in the rat cochlea. In micro-dissected tissue from the organ of Corti, spiral ganglion, and the membranous lateral wall, we found mRNA expression of the alpha7 and alpha9 subunits in the organ of Corti and alpha5-7, and beta2 and beta3 in the spiral ganglion using RT-PCR. Employing in situ hybridization with 35S-riboprobes, we localized alpha9 in hair cells regions and alpha6, alpha7 and beta2 in the type I cells of the spiral ganglion. No evidence of nAChR subunit mRNA expression was found in supporting cells, but beta2 was expressed in type II spiral ganglion cells, which are neither cholinergic nor cholinoceptive.
Sujet(s)
Cochlée/métabolisme , Récepteurs nicotiniques/biosynthèse , Animaux , Cochlée/innervation , Amorces ADN/métabolisme , Dendrites/métabolisme , Femelle , Cellules ciliées auditives externes/métabolisme , Hybridation in situ/méthodes , Structures macromoléculaires , Mâle , Souris , Neurofibres/métabolisme , Neurones efférents/métabolisme , Organe spiral/métabolisme , Réaction de polymérisation en chaîne/méthodes , Rats , Rat Sprague-Dawley , Récepteurs nicotiniques/composition chimique , Ganglion spiral/métabolismeRÉSUMÉ
The mRNA expression of the neuronal nicotinic acetylcholine receptor subunits was determined in adult rat vestibular end-organs and in Scarpa's ganglion (SCG) by in situ hybridization with [35S] riboprobes. Neurons in the SCG expressed the alpha 4-7 and beta 2-3 mRNAs, but not alpha 3 or beta 4 mRNAs. Not all SCG neurons expressed every mRNA found in SCG. The alpha 6 and beta 2-3 riboprobes labeled all neurons, but alpha 4, alpha 5, and alpha 7 mRNAs were selectively expressed in one or more subpopulations of SCG neurons. Vestibular sensory hair cells, in contrast, expressed only alpha 9 mRNA.
Sujet(s)
ARN messager/biosynthèse , Récepteurs nicotiniques/génétique , Nerf vestibulaire/métabolisme , Labyrinthe vestibulaire/métabolisme , Animaux , Femelle , Cellules ciliées vestibulaires/métabolisme , Hybridation in situ , Mâle , RatsRÉSUMÉ
The expression of an mRNA encoding a creatine transporter (CRT1) was investigated in the rat auditory system under ambient sound conditions, using radiolabeled and non-radiolabeled oligonucleotide in-situ hybridization. The results indicated that CRT1 mRNA is widely distributed in auditory nuclei, including the fusiform and deep layers of the dorsal cochlear nucleus, the ventral cochlear nucleus, the superior olivary complex, the nuclei of the lateral lemniscus and the inferior colliculus. The molecular layer of the dorsal cochlear nucleus and the medial geniculate have low levels of label. Creatine provides cells with a reservoir of high-energy phosphate. Neurons do not synthesize creatine but accumulate it by a transport mechanism, which is probably the limiting step in the regulation of intracellular creatine. Therefore, the quantity of transporter expressed may reflect the utilization of creatine and could serve as an in-vitro indicator of endogenous high-energy metabolism in some cells. Although most auditory nuclei express CRT1 mRNA, the quantity of CRT1 mRNA varies among auditory nuclei, indicating that many auditory nuclei have high and fluctuating energy requirements. The level of CRT1 transcript or protein may be regulated by chronic metabolic changes in the auditory system that may occur, for example, with damage to the acoustic organ or the aging process.
Sujet(s)
Cortex auditif/métabolisme , Tronc cérébral/métabolisme , Protéines de transport/métabolisme , Créatine/métabolisme , Protéines de transport membranaire , Animaux , Séquence nucléotidique , Transport biologique , Protéines de transport/génétique , Noyau cochléaire/imagerie diagnostique , Noyau cochléaire/métabolisme , Traitement d'image par ordinateur , Hybridation in situ , Colliculus inférieurs/imagerie diagnostique , Colliculus inférieurs/métabolisme , Marquage isotopique , Mâle , Données de séquences moléculaires , Sondes oligonucléotidiques , Noyau olivaire/imagerie diagnostique , Noyau olivaire/métabolisme , Phosphates/métabolisme , ARN messager/métabolisme , Radiographie , Rats , Rat Sprague-Dawley , Coloration et marquageRÉSUMÉ
The neurotransmitter at the synapses between hair cells and spiral ganglion cells in the cochlea is probably L-glutamate or a similar excitatory amino acid. Glutamate uptake by nerve terminals and glial cells is an important component of neurotransmission at glutamatergic synapses of the central nervous system, for providing a reservoir of transmitter or transmitter precursors and the termination of the released glutamate. Hair cell synapses are not surrounded by glial cells, therefore, the uptake mechanism for glutamate in the cochlea may be unique. cDNA was synthesized from total RNA isolated separately from the rat organ of Corti, spiral ganglia, and lateral wall tissues. The expression of a glutamate/aspartate transporter (GLAST) was detected by DNA amplification with the polymerase chain reaction. The other two members of glutamate transporters in this family were not detected by this method. A partial cDNA encoding to GLAST was identified by sequence analysis in a rat cochlear cDNA library. Data concerning the expression and the molecular structure of the glutamate transporter GLAST in the cochlea may provide important information regarding the neurotransmission process at the hair cell-afferent synapses.
Sujet(s)
Protéines de transport/biosynthèse , Cochlée/métabolisme , Régulation de l'expression des gènes/génétique , Acide glutamique/métabolisme , Glycoprotéines/biosynthèse , Transmission synaptique/génétique , Séquence d'acides aminés , Système X-AG de transport d'acides aminés , Animaux , Séquence nucléotidique , Protéines de transport/composition chimique , Protéines de transport/génétique , Amorces ADN/composition chimique , ADN complémentaire/biosynthèse , ADN complémentaire/composition chimique , ADN complémentaire/génétique , Électrophorèse sur gel d'agar , Banque de gènes , Glycoprotéines/composition chimique , Glycoprotéines/génétique , Cellules ciliées auditives/métabolisme , Techniques in vitro , Données de séquences moléculaires , Névroglie/physiologie , Cadres ouverts de lecture , Organe spiral/métabolisme , Réaction de polymérisation en chaîne , ARN/biosynthèse , ARN/génétique , Rats , Rat Sprague-Dawley , Ganglion spiral/métabolisme , Transmission synaptique/physiologieRÉSUMÉ
Confocal laser scanning microscopy and immunofluorescence were used to detect gentamicin at the single cell level in the sensory cells of the guinea-pig hearing organ after a chronic systemic treatment. Gentamicin uptake by the hair cells precedes largely the manifestation of hearing impairment. We demonstrate that for a non-ototoxic treatment the captured gentamicin is eliminated in two phases: one rapid and one slow with approximate half-life of 2 days and 5-6 months, respectively. These novel observations should be of primary importance for new rational approaches to both the mechanism of ototoxicity and therapeutic strategies for the treatment of infectious diseases requiring the aminoglycoside antibiotics.
Sujet(s)
Gentamicine/pharmacocinétique , Cellules ciliées auditives/métabolisme , Organe spiral/cytologie , Animaux , Femelle , Technique d'immunofluorescence , Cochons d'Inde , Techniques in vitro , Lasers , Microscopie électronique à balayage/méthodesRÉSUMÉ
Recent experiments using autoradiographic and immunohistochemical labelling of gentamicin have demonstrated that GM penetrates specifically into the sensory cells of the inner ear, with a good correlation between the intensity of the labelling and the respective degrees and localisations of ototoxic damages. In the sensory hair cells GM ils localised below the cuticular plate, in an area rich in lysosomes during the ototoxic treatment. This penetration precedes the development of ototoxicity and there seems to be a threshold of intracellular concentration of GM for development of intracellular ototoxic processes. Clearance is very slow since GM can still be observed 11 months after the end of a non toxic treatment (60 mg/kg/day for 6 consecutive days). This observation is of clinical interest, in view of the delayed development of ototoxicity often observed clinically, and with respect to other hazards, including new ototoxic treatments, to which the cells can be exposed while loaded with the aminoglycoside molecule.
Sujet(s)
Antibactériens/effets indésirables , Cochlée/effets des médicaments et des substances chimiques , Gentamicine/pharmacocinétique , Cellules ciliées auditives internes/effets des médicaments et des substances chimiques , Autoradiographie , Gentamicine/effets indésirables , Cellules ciliées auditives internes/ultrastructure , Troubles de l'audition/induit chimiquement , Humains , Immunohistochimie , Taux de clairance métabolique , Microscopie de fluorescenceRÉSUMÉ
Immunodetection of gentamicin (GM) was carried out on surface preparations of the whole organ of Corti from cochleas of guinea pigs treated daily with GM at a dose of 60 mg/kg/day and sacrificed at the end of different treatment periods. Cochlear function was determined just before sacrifice, 24 h after the last injection. Threshold elevations, mainly at high frequencies, were noted only after 10-14 days of treatment. However, the presence of GM was observed much earlier, as early as after the second injection, and specifically in the sensory hair cells. GM labelling was essentially observed in the outer hair cells (OHC) and increased from the apex to the base of the cochlea and from the third to the first row of OHC. GM labelling of inner hair cells was less pronounced and was observed only after the 8th day of treatment. These observations demonstrate that GM specifically enters and accumulates in the sensory hair cells and that the uptake precedes the development of functional and cellular damage which may result from a long-term intracellular cytotoxic action of the molecule.
Sujet(s)
Cochlée/effets des médicaments et des substances chimiques , Gentamicine/pharmacocinétique , Cellules ciliées auditives/effets des médicaments et des substances chimiques , Surdité neurosensorielle/induit chimiquement , Animaux , Test ELISA , Potentiels évoqués auditifs , Femelle , Gentamicine/administration et posologie , Cochons d'Inde , Surdité neurosensorielle/diagnostic , Immunoglobuline G/pharmacologie , Organe spiral/immunologieRÉSUMÉ
Guinea pigs (GPs) receiving one intra-muscular injection of gentamicin (GM) (150 mg/kg) in which 2 mg of tritiated GM (2 mCi) were incorporated, followed 1.5 h later by an intra-cardiac injection of ethacrynic acid (EA) (30 mg/kg) were sacrificed 25 min, 1, 4 and 24 h after the EA injection. Other GPs were treated with one injection of GM or EA alone and sacrificed 24 h later. Cochlear function was monitored by recording VIIIth nerve compound action potential (CAP) responses to clicks at 70 dB peak-equivalent Sound Pressure Level (pe SPL) and CAP audiograms. At 24 h thresholds were significantly elevated for high frequencies only in GPs treated with the GM/EA combination. GM was revealed in the cochlea and kidney by autoradiography using light and electron microscopy. In the kidney GM was already detected in the proximal tubule cells at 25 min and at 24 h. In the cochlea GM was systematically not observed at 25 min. At 1 h a weak labelling was detected in vessels of the stria vascularis and in sensory cells at the base of the cochlea. At 4 h the labelling disappeared in stria vascularis but increased in the hair cells. At 24 h GM labelling was found exclusively in hair cells, particularly outer hair cells, with a gradient from base to apex and from first to 3rd row, this distribution pattern correlating well with the pattern of threshold changes prominent at high frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)
Sujet(s)
Cochlée/métabolisme , Gentamicine/pharmacocinétique , Potentiels d'action/effets des médicaments et des substances chimiques , Animaux , Seuil auditif/effets des médicaments et des substances chimiques , Transport biologique actif , Cochlée/effets des médicaments et des substances chimiques , Cochlée/anatomopathologie , Interactions médicamenteuses , Acide étacrynique/administration et posologie , Acide étacrynique/toxicité , Femelle , Gentamicine/administration et posologie , Gentamicine/toxicité , Cochons d'Inde , Cellules ciliées auditives/métabolisme , Histocytochimie , Rein/métabolisme , Fractions subcellulaires/métabolismeRÉSUMÉ
Presence of gentamicin (GM) in cochlear hair cells was detected by immunohistochemistry in guinea pigs (GPs) cochlea 1, 9 and 41 days after a 6-day treatment with GM at 60 mg/kg/day (s.c.). The number of GPs in each group was respectively 7, 12 and 6. Twelve other non-treated GPs served as controls. Cochlear function was measured, just before sacrifice, by VIIIth nerve compound action potential (CAP) audiograms. Functional and immunohistological evaluations were performed by two independent naïve observers respectively. Functional changes were minimal: only one out of the 25 treated GPs, from the 41-day group, showed significant threshold elevations on high frequencies. Meanwhile GM labelling was observed in most outer hair cells (OHCs) from the three rows of all the treated GPs, with radial and longitudinal gradients, and found similar in the 3 groups. These results 1) confirm that GM is significantly present in OHCs before the development of ototoxicity and 2) indicate that GM accumulates and is maintained inside the OHCs for very long periods of time, i.e. that its clearance from the hair cells, if any, would be very slow.
Sujet(s)
Gentamicine/pharmacocinétique , Cellules ciliées auditives/métabolisme , Animaux , Potentiels microphoniques cochléaires/effets des médicaments et des substances chimiques , Relation dose-effet des médicaments , Gentamicine/toxicité , Cochons d'Inde , Cellules ciliées auditives/effets des médicaments et des substances chimiques , Techniques immunoenzymatiquesRÉSUMÉ
The in vitro motility and viability of outer hair cells isolated from cochleae of normal control guinea pigs have been compared to that of guinea pigs exposed, just before sacrifice, to low-frequency high-intensity noise inducing acute 30 dB thresholds shifts at all frequencies below 10 kHz. The results indicate that the cells' viability is shortened, their contractile response to Ca2+/ATP reduced, while their electrically-induced motility is not modified. These experiments demonstrate that in vivo cochlear dysfunction can correlate with changes in in vitro outer hair cell's properties. Thus the morphological and "functional" investigation of hair cells in vitro can be a valuable approach to the study of cochlear physiopathology. Here the acoustic overstimulation seems to have modified the outer hair cells' Ca2+/ATP dependent slow contractile apparatus in a way which could modify in turn their mechanical excitation by the noise.
Sujet(s)
Cellules ciliées auditives/physiologie , Son (physique) , Adénosine triphosphate/pharmacologie , Animaux , Seuil auditif , Calcium/pharmacologie , Mouvement cellulaire , Séparation cellulaire , Survie cellulaire , Stimulation électrique , Cochons d'Inde , Cellules ciliées auditives/cytologie , Cellules ciliées auditives/effets des médicaments et des substances chimiques , Potassium/pharmacologieRÉSUMÉ
Regional selectivity of gentamicin (GM) ototoxicity was studied in guinea pigs (GPs) using electrophysiological, morphological, autoradiographic and immunohistological observations following combined treatment with GM (150 mg/kg i.m.) and ethacrynic acid (EA) (30 mg/kg i.c. or i.v., 1.5 h after GM injection). The GPs were either continuously stimulated every 5 min with a series of 256 clicks (70 dB peSPL, 10/s) during 3 h for monitoring fast changes in VIII nerve compound action potential (CAP) after the EA injection, and thereafter kept in the animal quarters (background noise of 60 dB SPL) (group I), or similarly monitored for only 10 min after the EA injection and thereafter kept in a soundproof room (around 0 dB SPL) (group II). Whenever GM labelling was observed it was localized only in the sensory hair cells. From 3 h after EA injection, the GPs in group I presented threshold elevations in the high-frequency region, which progressed to 60-80 dB at all frequencies at and after 48 h. Parallel to the threshold pattern, GM uptake in outer hair cells (OHCs) was seen with an increasing concentration from apex toward base from 3 to 24 h, while after 48 h almost all OHCs were destroyed and inner hair cells (IHCs) were marked by GM. In group II no changes in CAP thresholds were observed until more than 24 h, although GM was detected in the hair cells from 6 h on. At this early stage, the distribution of GM lacked a clear pattern, particularly without a clear apex-base gradient, and GM deposits were found only around the basal body. However in both groups, in late stage (greater than 24 h), the base-apex gradient was more pronounced and GM was found throughout the cell body, with a marked concentration below the cuticular plate. These results suggest that GM may penetrate hair cells around the basal body and that activating the cells by sound potentiates both GM uptake and its intracellular toxicity.
Sujet(s)
Cochlée/effets des médicaments et des substances chimiques , Acide étacrynique/toxicité , Gentamicine/toxicité , Nerf vestibulocochléaire/effets des médicaments et des substances chimiques , Stimulation acoustique , Potentiels d'action/effets des médicaments et des substances chimiques , Animaux , Autoradiographie , Cochlée/physiopathologie , Interactions médicamenteuses , Acide étacrynique/pharmacocinétique , Gentamicine/pharmacocinétique , Cochons d'Inde , Cellules ciliées auditives/effets des médicaments et des substances chimiques , Cellules ciliées auditives/métabolisme , Cellules ciliées auditives/ultrastructure , Cellules ciliées auditives internes/effets des médicaments et des substances chimiques , Cellules ciliées auditives internes/ultrastructure , Immunohistochimie , Microscopie électronique à balayage , Monitorage physiologique , Nerf vestibulocochléaire/physiopathologieRÉSUMÉ
VIII nerve compound action potentials evoked by electrical stimulation are decomposed in series of pure-tone derived potentials using masking. These potentials are in turn decomposed in a series of contributions from various frequency bands by adding high-pass masking noises. The amplitudes of the derived signals are thought to be proportional to the number of fibres activated by the masking acoustical stimulations. Thus the density of nerve fibres stimulated along the basilar membrane by pure tones as a function of frequency and intensity can be estimated.
Sujet(s)
Audiométrie tonale , Audiométrie , Masquage perceptif/physiologie , Nerf vestibulocochléaire/physiologie , Animaux , Stimulation électrique , Cochons d'IndeRÉSUMÉ
Electrically-evoked VIIIth nerve CAP responses evoked by electrical stimulation and derived by masking with sounds are recorded in the guinea pig, using different masking paradigms (pure tones and high-pass filtered white noise). CAP frequency threshold curves correlate with threshold curves determined by other means, in normal as well as in pathological guinea pigs. Amplitudes of the responses as a function of pure tones frequency and intensity are also measured. Such measurements provide an estimate of the number of fibers activated by the pure tones. These responses can be further analysed using masking with high-pass filtered white noise.