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PubMed1979

Morphometry of the chinchilla organ of Corti and stria vascularis.

This research describes a procedure for a morphometric analysis of the organ of Corti and stria vascularis in the chinchilla. In nine normal cochleae the length of the basilar membrane and the stria vascularis measured 18.47 and 25.22 mm, respectively. An average of 1910 inner and 7501 outer hair cells were present while an average of 15 inner and 90 outer hair cells were absent. In all cochleae examined there were always some missing hair cells in varying numbers even though the animals had no known ototoxic exposure. Stria area, width and thickness increased from the cochlear apex toward the base. Consistency of changes in stria dimensions among animals was enhanced by expressing position in terms of percentage stria length rather than distance as such. Total stria volume was estimated at 0.15 microliter.

Animals↗
PubMed1986

GABA-like immunoreactivity in the squirrel monkey organ of Corti.

The distribution of gamma-aminobutyric acid (GABA)-like immunoreactivity in the squirrel monkey organ of Corti was determined using an antiserum against GABA conjugated to bovine serum albumin. Immunoreactive labeling was seen in the region of the inner spiral bundle, the synaptic region below inner hair cells, in terminals contacting the basal part of outer hair cells, and in tunnel spiral fibers. Examples of each of these immunoreactive components could be observed in all cochlear turns. In the region of inner hair cells, immunoreactive labeling took the form of numerous small puncta randomly distributed below the base of the cells. In the region of outer hair cells, large globular immunoreactive structures reminiscent of terminal endings at the subnuclear level were observed. Since similar structures were seen at the base of outer hair cells in other cochleas processed for AChE, we conclude that GABA-like immunoreactivity was contained in efferent terminals which synapse on outer hair cells. These results strengthen previous evidence for the presence of GABA in the olivocochlear system of the mammalian cochlea.

Acetylcholinesterase↗
PubMed1990

Comparison of low- and high-side two-tone suppression in inner hair cell and organ of Corti responses.

Two-tone interactions were measured from inner hair cells and from the organ of Corti fluid space in the third turn of the guinea pig cochlea. At relatively low stimulus levels, a low-side suppressor caused frequency response functions to become broader. Phase changes exhibited a lag/lead transition around the characteristic frequency in harmony with the change in magnitude. These patterns are similar to those previously documented for a high-side suppressor (Cheatham and Dallos 1989) and suggest that suppression is not simply an attenuation phenomenon since level reductions for single-tone inputs produce response patterns which are mirror images of those obtained for the two-tone conditions. In contrast to the low-level results, data measured at moderately high stimulus levels indicate that the magnitude changes produced by both low- and high-side suppressors are qualitatively similar to changes generated by reducing the input sound level. In other words, ac frequency response functions become narrower, partially reversing the broadening of these functions which occurs as sound level increases. Companion phase measures, however, demonstrate that low- and high-side suppressors, in spite of producing similar changes in filter shape, do not produce similar changes in response phase. In fact, neither of the two-tone conditions produce response patterns similar to the one associated with reducing the input sound level.

Acoustic Stimulation↗
PubMed1995

The localization of taurine-like immunoreactivity in the organ of Corti: a semiquantitative, post-embedding immuno-electron microscopic analysis in the rat with some observations in the guinea pig.

The cellular and subcellular localization of taurine in the organ of Corti was examined by means of postembedding immunocytochemistry. Supporting cells, including border cells, inner phalangeal cells, Deiters cells, pillar cells, and Böttcher cells are enriched in taurine-like immunoreactivity, contrasting sharply with inner and outer hair cells which did not show noteworthy immunolabelling. Immunogold cytochemistry indicated an even distribution of taurine throughout the cytoplasm and karyoplasm of the labelled supporting cells. Rats and guinea pigs showed similar labelling patterns. The present immunocytochemical findings indicate that supporting cells are the plausible sources of the reported potassium-induced taurine release in the cochlea. The distribution of taurine in the organ of Corti is not compatible with a transmitter or neuromodulatory action of this amino acid, but rather suggests an involvement in osmoregulatory functions.

Animals↗
PubMed2004

Organ of Corti potentials and the motion of the basilar membrane.

During sound stimulation, receptor potentials are generated within the sensory hair cells of the cochlea. Prevailing theory states that outer hair cells use the potential-sensitive motor protein prestin to convert receptor potentials into fast alterations of cellular length or stiffness that boost hearing sensitivity almost 1000-fold. However, receptor potentials are attenuated by the filter formed by the capacitance and resistance of the membrane of the cell. This attenuation would limit cellular motility at high stimulus frequencies, rendering the above scheme ineffective. Therefore, Dallos and Evans (1995a) proposed that extracellular potential changes within the organ of Corti could drive cellular motor proteins. These extracellular potentials are not filtered by the membrane. To test this theory, both electric potentials inside the organ of Corti and basilar membrane vibration were measured in response to acoustic stimulation. Vibrations were measured at sites very close to those interrogated by the recording electrode using laser interferometry. Close comparison of the measured electrical and mechanical tuning curves and time waveforms and their phase relationships revealed that those extracellular potentials indeed could drive outer hair cell motors. However, to achieve the sharp frequency tuning that characterizes the basilar membrane, additional mechanical processing must occur inside the organ of Corti.

Acoustic Stimulation↗
PubMed1980

Organ of Corti: observation technique in the living animal.

This paper describes a new technique for visualizing the organ of Corti in the living guinea pig. The various cell types and blood supply can be viewed at magnifications up to 625X through a microscope, as seen reflected by a tiny mirror in scala vestibuli. Glass microelectrodes can also be seen as they penetrate the tissues, and can be accurately localized.

Animals↗
PubMed1985

Electron microscopic localization of N-terminal proenkephalin (synenkephalin) immunostaining in the guinea pig organ of Corti.

Using a pre-embedding immunoelectron microscopic technique, anti-synenkephalin immunostaining has been demonstrated within efferent varicosities (originating from the brainstem) of the inner spiral bundle and the tunnel spiral bundle of the organ of Corti. Axodendritic synapses were observed between the anti-synenkephalin immunostained varicosities and auditory dendrites connected to inner hair cells. No anti-synenkephalin immunostaining was found in any efferents at the outer hair cell level. We suggest that this immunolocalization of synenkephalin in the organ of Corti allows a better differentiation of the cochlear efferent systems on a neurochemical basis. The whole lateral system, or at least a significant part of it, could be referred to as the 'enkephalin-containing efferent system'.

Animals↗
PubMed1990

Lectin staining of saccharides in the normal and hypothyroid developing organ of Corti.

Lectin staining has been used to detect mono- and oligosaccharides in normal and hypothyroid developing organs of Corti in the rat. Eight developmental stages were studied (1, 5, 8, 10, 15, 20, 50 and 60 days after birth). Congenital hypothyroidism was induced by oral administration of propylthyouracil to pregnant rats. Labelling of the tectorial membrane with 3 lectins, Ulex europaeus agglutinin-I (UEA-I), Lens culinaris agglutinin (LCA) and Ricinus communis agglutinin-I (RCA-I) showed no significant differences between normal and hypothyroid animals. Staining with peanut agglutinin (PNA) showed that the hypothyroid adult tectorial membrane (but not the normal one) possesses the disaccharide galactose + N-acetyl galactosamine. Phaseolus vulgaris agglutinin-L (PHA-L) labels the whole tectorial membrane in both groups of animals, but the staining is more intense in the hypothyroid one for a narrow band of oligosaccharide located just between the tectorial membrane and the underlying organ of Kölliker. Both soybean agglutinin (SBA) and succinylated wheat germ agglutinin (WGA) stain the tectorial membrane as well as the cytoplasm of the cells constituting the inner portion of the organ of Kölliker; this latter feature disappears in the normal animals about the 8th postnatal day, but it is abnormally preserved until the 60th postnatal day in the hypothyroid ones. In the adult hypothyroid animals, 3 of the lectins (LCA, PHA-L and WGA) stain extracellular conglomerates located under the synaptic pole of the outer hair cells.

Animals↗
PubMed1999

Application of a platinum replica method to the study of the cytoskeleton of isolated hair cells, supporting cells and whole mounts of the organ of Corti.

We adapted a method of platinum replica to study the cytoskeleton of isolated cells of the guinea pig organ of Corti. This technique combined high image resolution with the ability to visualize the three-dimensional organization of the cytoskeleton of a whole cell. The procedure includes: isolation of hair cells and supporting cells using collagenase digestion, attachment of the cells to a coverslip, detergent extraction, chemical fixation, critical point drying, platinum/carbon coating, and transmission electron microscopy analysis. By using the method of platinum replica, we confirmed the existence of structural domains in the cortical lattice of outer hair cells. Based on the analysis of the partly destroyed cortical lattice, we propose that circumferential filaments are underlined with a thin flexible network. In addition, we established that the base of each stereocilium had a cone-like expansion of actin filaments and was surrounded by a thin bundle of filaments. We also produced replicas of the protrusion of the cuticular plate into the cytoplasm (infracuticular network) and the reticular lamina cytoskeleton. Our data indicated that the platinum replica method is useful for studying structural interactions among different cytoskeletal elements in the reticular lamina, as well as the cortex of outer hair cells and the cytoskeleton of supporting cells.

Animals↗
PubMed1985

Localization of calcitonin gene-related peptide in the organ of Corti of the rat: an immunohistochemical study.

The localization of calcitonin gene-related peptide (CGRP)-like immunoreactive (CGRPI) structures in the cochlea was examined in the rat using immunocytochemistry. Numerous CGRPI fibers entered the organ of Corti in the intraganglionic spiral bundle and formed a dense fiber patch at the base of the inner hair cells. Much fewer, but still a significant number of CGRPI fibers were seen at the synaptic region of the outer hair cells. Since no immunoreactive cells were seen in the organ of Corti and spinal ganglion, these fibers may be one of the major components of the olivocochlear bundles originated from the superior olivary complex.

Animals↗
PubMedDate not supplied

Incidence of reciprocal synapses on outer hair cells of the human organ of Corti.

The incidence of reciprocal synapses at the base of outer hair cells of the human organ of Corti was studied by electron-microscopic serial section reconstruction. Reciprocal synapses were found in each of six ears from five individuals. A total of 1,386 serial sections and the neural poles of 25 outer hair cells in two individuals were examined. Fourteen of the 25 outer hair cells (56%) possessed reciprocal synapses. The incidence of reciprocal synapses increased from the first to the third rows of outer hair cells, as determined by the percentage of outer hair cells and afferent nerve terminals of each row demonstrating reciprocal synapses and the average number of reciprocal synapses per hair cell in each row. Hair cells with reciprocal synapses had more afferent and fewer efferent terminals per hair cell than hair cells without reciprocal synapses.

Afferent Pathways↗
PubMed1982

Intracellular and extracellular responses in the organ of Corti of the gerbil.

Techniques have been developed for recording from and staining cells in the organ of Corti of the Mongolian gerbil. Using physiological criteria as in the guinea pig, the cells were classified as either supporting cells or inner hair cells (IHCs). In addition, several IHCs were stained using HRP and identified in surface preparations. Extracellular responses in the vicinity of IHCs were tuned as sharply as auditory-nerve fibers. Intracellular tuning curves of IHCs were equally sharp near their tips. However, the tip-to-tail distances and sensitivities appeared to be somewhat reduced, presumably due to trauma caused by the recording electrode. Intensity functions, relating receptor depolarization to stimulus intensity level, were obtained for the IHCs. The functions have a consistent quantitative form for frequencies equal to or less than the characteristic frequency of a cell. At low stimulus levels the response increases in proportion to energy, i.e. the square of the sound pressure level. At high levels the response increases more slowly, but shows a greater operating range, and smaller effects of saturation, than do the steady-state responses of single auditory-nerve fibers.

Animals↗
PubMed1988

Cation distribution in the organ of Corti of the guinea pig.

Cations were precipitated with potassium antimonate in the cochlea of the guinea pig and the distribution of the formed precipitates was studied by electron microscopy. The precipitate density in different cells of the organ of Corti was determined on electron micrographs by counting numbers of precipitates per unit area. The spatial distribution of the precipitates was also determined by electron spectroscopic imaging (ESI). Significant differences were found among the cells of the same tissue being analyzed. These precipitate-rich cells may play a role in a postulated current flow in the organ of Corti.

Animals↗
PubMed1987

Differences in the distribution of F-actin in outer hair cells along the organ of Corti.

There is evidence of differences in the structure, innervation and physiological responses between outer hair cells (OHCs) of the basal and apical turns of the mammalian cochlea. In this study we have used rhodamine-labelled phalloidin to investigate the differential distribution of F-actin in OHCs along the organ of Corti of the guinea pig. Isolated OHCs and surface preparations and cryosections of the organ of Corti were studied. F-actin was observed in stereocilia and the cuticular plate of all OHCs. In addition, some OHCs had a network of F-actin extending from the cuticular plate towards the nucleus. This infracuticular network was observed in most OHCs of the apical cochlear turns but was not seen in any OHCs of the basal turn. These microstructural differences between OHCs of the base and apex could be related to differences in OHC function between the apical and basal portions of the cochlea.

Actins↗
PubMed2001

[Study on voltage-sensitive current of spiral ganglion cells in mice organ of Corti culture].

OBJECTIVE: To investigate the property of voltage-sensitive current in cochlear spiral ganglion cells of the C57BL/10J mice, an inbred strain which develops early onset hearing loss. METHODS: Organotypic cultures of organ of Corti were prepared from neonatal mice 0-5 days of age. Whole-cell current and voltage clamp techniques were used to study Na+, K+ and Ca2+ currents of the spiral ganglion cells in culture. RESULTS: Cultures were maintained for 8-48 hours before use. Ganglion cells were identified first through their anatomical positions and finally through fast negative Na+ current. Spontaneous action potentials were recorded from some ganglion cells (4 out of 39). When present, spontaneous rates were around 20 spikes/sec, and might be as high as 135 spikes/sec. The mean resting potential was (-55 +/- 5) mV (n = 39). Under voltage clamp conditions, transient inward currents (negative) and outward (positive), steady-state voltage-dependent currents were recorded in normal HBSS. Rapid inward currents were totally blocked by 300 nM TTX applied locally to the culture. Inward currents recovered quickly after TTX wash out suggesting that the transient inward current was carried by Na+. The mean maximum amplitude of Na+ current was (-2.0 +/- 1.1) nA (n = 39) recorded in HBSS. Adding TEA (10 mmol/L) and 4-AP (0.15 mmol/L) to the bath solution or replacing K+ with Ca+ in the pipette solution partly blocked the sustained outward current. This suggests that the outward current was carried by K+. The mean maximum amplitude of K+ was (3.0 +/- 1.3) nA (n = 39) with 140 mM K+ in the pipette. Inward Ca2+ current was recorded in Ba2+ solution which mean peak amplitude was (-1.0 +/- 0.7) nA (n = 20). Ca2+ currents were reversibly blocked by 100 microM Cd2+. CONCLUSION: Whole cell recordings from spiral ganglion neurons can be obtained from organotypic cultures of the organ of Corti. Fast Na+ current, sustained K+ current and L-type Ca2+ current were recorded in the spiral ganglion cells cultured for 1-2 days. Whole cell recording showed that cochlea spiral ganglion cells can generate spontaneous action potential one day after birth and the firing rates could reach levels equal to those recorded in vivo.

Action Potentials↗
PubMed1995

Patch clamped responses from outer hair cells in the intact adult organ of Corti.

Outer hair cells (OHCs) from the mammalian cochlea act as both sensory cells and motor cells. We report here whole-cell tight seal recordings of OHC activity in their natural embedding tissue, the intact organ of Corti, using a temporal bone preparation. The mean cell resting potential, -76 +/- 4 mV (n = 19) and input conductance (10 +/- 3 nS at -70 mV) of third turn hair cells were significantly lower than have been found in isolated cells. Two main K+ currents in the cell were identified. One current, activated positive to -100 mV, was reduced by 5 mM BaCl2. The other current, activated above -40 mV, was reduced by 100 microM 4-aminopyridine (4-AP) and by 30 mM tetraethylammonium (TEA). Both of these currents have been also identified in recordings reported from isolated cells. On stepping to different membrane potentials, cells imaged in the organ of Corti changed length by an amount large enough to cause visible distortions in neighbouring cells. By quantifying such distortions we estimate that the forces generated by OHCs can account for the enhanced response to sound required by the cochlear amplifier.

Animals↗