scholarly journals Axodendritic versus axosomatic cochlear efferent termination is determined by afferent type in a hierarchical logic of circuit formation

2021 ◽  
Vol 7 (4) ◽  
pp. eabd8637
Author(s):  
Jemma L. Webber ◽  
John C. Clancy ◽  
Yingjie Zhou ◽  
Natalia Yraola ◽  
Kazuaki Homma ◽  
...  
Keyword(s):  
Hair Cells ◽  
Fiber Type ◽  
Afferent Fiber ◽  
Outer Hair Cells ◽  
Type I ◽  
Type Ii ◽  
Efferent Neurons ◽  
Distinct Pair ◽  
Mechanosensory Hair Cells ◽  
Circuit Formation

Hearing involves a stereotyped neural network communicating cochlea and brain. How this sensorineural circuit assembles is largely unknown. The cochlea houses two types of mechanosensory hair cells differing in function (sound transmission versus amplification) and location (inner versus outer compartments). Inner (IHCs) and outer hair cells (OHCs) are each innervated by a distinct pair of afferent and efferent neurons: IHCs are contacted by type I afferents receiving axodendritic efferent contacts; OHCs are contacted by type II afferents and axosomatically terminating efferents. Using an Insm1 mouse mutant with IHCs in the position of OHCs, we discover a hierarchical sequence of instructions in which first IHCs attract, and OHCs repel, type I afferents; second, type II afferents innervate hair cells not contacted by type I afferents; and last, afferent fiber type determines if and how efferents innervate, whether axodendritically on the afferent, axosomatically on the hair cell, or not at all.

scholarly journals Unmyelinated type II afferent neurons report cochlear damage

2015 ◽  
Vol 112 (47) ◽  
pp. 14723-14727 ◽  
Author(s):  
Chang Liu ◽  
Elisabeth Glowatzki ◽  
Paul Albert Fuchs
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Outer Hair Cell ◽  
Cell Damage ◽  
Large Diameter ◽  
Outer Hair Cells ◽  
Type I ◽  
Type Ii ◽  
Inner Hair Cell ◽  
Hair Cell Damage

In the mammalian cochlea, acoustic information is carried to the brain by the predominant (95%) large-diameter, myelinated type I afferents, each of which is postsynaptic to a single inner hair cell. The remaining thin, unmyelinated type II afferents extend hundreds of microns along the cochlear duct to contact many outer hair cells. Despite this extensive arbor, type II afferents are weakly activated by outer hair cell transmitter release and are insensitive to sound. Intriguingly, type II afferents remain intact in damaged regions of the cochlea. Here, we show that type II afferents are activated when outer hair cells are damaged. This response depends on both ionotropic (P2X) and metabotropic (P2Y) purinergic receptors, binding ATP released from nearby supporting cells in response to hair cell damage. Selective activation of P2Y receptors increased type II afferent excitability by the closure of KCNQ-type potassium channels, a potential mechanism for the painful hypersensitivity (that we term “noxacusis” to distinguish from hyperacusis without pain) that can accompany hearing loss. Exposure to the KCNQ channel activator retigabine suppressed the type II fiber’s response to hair cell damage. Type II afferents may be the cochlea’s nociceptors, prompting avoidance of further damage to the irreparable inner ear.

scholarly journals Efferent synaptic transmission at the vestibular type II hair cell synapse

2020 ◽  
Vol 124 (2) ◽  
pp. 360-374 ◽  
Author(s):  
Zhou Yu ◽  
J. Michael McIntosh ◽  
Soroush G. Sadeghi ◽  
Elisabeth Glowatzki
Keyword(s):  
Hair Cells ◽  
Nerve Fibers ◽  
Type I ◽  
Type Ii ◽  
Vestibular Hair Cells ◽  
Efferent Neurons ◽  
The Brain ◽  
Cell Synapse ◽  
Stimulation Of

Type II vestibular hair cells (HCs) receive inputs from efferent neurons in the brain stem. We used in vitro optogenetic and electrical stimulation of vestibular efferent fibers to study their synaptic inputs to type II HCs. Stimulation of efferents inhibited type II HCs, similar to efferent effects on cochlear HCs. We propose that efferent inputs adjust the contribution of signals from type I and II HCs to vestibular nerve fibers.

scholarly journals Muscle Changes in Lambs with Surgically Created Scoliosis Produced in Utero

1978 ◽  
Vol 5 (3) ◽  
pp. 283-287 ◽  
Author(s):  
G.M. Kent ◽  
W. Zingg ◽  
D. Armstrong
Keyword(s):  
Musculoskeletal Diseases ◽  
Fiber Type ◽  
Surgical Techniques ◽  
Spinal Curvature ◽  
Surgical Trauma ◽  
Developmental Defect ◽  
Type I ◽  
Type Ii ◽  
Muscle Changes ◽  
Type Ii Fibers

SUMMARY:Spinal curves may be produced in fetal lambs with three surgical techniques. These procedures vary from mere exposure of the costo-vertebral junction of three ribs through a paravertebral incision, to resection of the head and part of the adjacent shaft of three ribs. The fetal age varies from forty-nine to seventy-three days. The degree of curvature present at birth seems to increase in severity with decreasing fetal age at the time of surgery, but the type of surgical procedure does not appear to influence the severity of the curve, suggesting that the mechanical presence of the ribs does not prevent the development of scoliosis in these animals.Histological studies of the m. longissimus dorsi at the apices of the curves reveal two main types of abnormality in the muscle fibers. Both Type I and Type II fibers were significantly reduced in size in the biopsies taken from the side on which the surgery was performed, and there was marked alteration in the proportion of one fiber type to the other in most biopsies taken from both operated sides when compared with biopsies from unoperated twin animals.The fetal age and amount of surgical trauma appeared to play no role in the degree of muscle alteration, suggesting that even minimal surgical trauma to the paraspinal region at any fetal age between 49–73 days is sufficient to produce significant muscle fiber abnormality and spinal curvature.A parallel is drawn between these muscle findings and those in a number of human musculoskeletal diseases, and suggests the possibility of a developmental defect in the pathogenesis of these diseases.

Rostrocaudal pattern of fiber-type changes in an overloaded rat ankle extensor

1991 ◽  
Vol 71 (2) ◽  
pp. 558-564 ◽  
Author(s):  
P. F. Gardiner ◽  
B. J. Jasmin ◽  
P. Corriveau
Keyword(s):  
Fiber Type ◽  
Muscle Length ◽  
Similar Degree ◽  
Complex Nature ◽  
Type I ◽  
Fiber Types ◽  
Type Ii ◽  
Cross Sectional ◽  
Hypertrophic Response ◽  
Type I Fibers

Our aim was to quantify the overload-induced hypertrophy and conversion of fiber types (type II to I) occurring in the medial head of the gastrocnemius muscle (MG). Overload of MG was induced by a bilateral tenotomy/retraction of synergists, followed by 12–18 wk of regular treadmill locomotion (2 h of walking/running per day on 3 of 4 days). We counted all type I fibers and determined type I and II mean fiber areas in eight equidistant sections taken along the length of control and overloaded MG. Increase in muscle weights (31%), as well as in total muscle cross-sectional areas (37%) and fiber areas (type I, 57%; type II, 34%), attested to a significant hypertrophic response in overloaded MG. An increase in type I fiber composition of MG from 7.0 to 11.5% occurred as a result of overload, with the greatest and only statistically significant changes (approximately 70–100%) being found in sections taken from the most rostral 45% of the muscle length. Results of analysis of sections taken from the largest muscle girth showed that it significantly underestimated the extent of fiber conversion that occurred throughout the muscle as a whole. These data obtained on the MG, which possesses a compartmentalization of fiber types, support the notion that all fiber types respond to this model with a similar degree of hypertrophy. Also, they emphasize the complex nature of the adaptive changes that occur in these types of muscles as a result of overload.

Guinea Pig Vestibular Type I Hair Cells Can Show Reversible Shortening

1991 ◽  
Vol 1 (3) ◽  
pp. 241-250
Author(s):  
Pascale N.M. Lapeyre ◽  
Yves Cazals
Keyword(s):  
Guinea Pig ◽  
Hair Cells ◽  
Neck Region ◽  
Outer Hair Cells ◽  
Test Solution ◽  
Induced Response ◽  
Type I ◽  
Hypotonic Solution ◽  
Bathing Medium ◽  
Water Influx

Guinea pig isolated vestibular type I hair cells (VIHCs) were recently reported by our group to respond to high [KCl] solutions by an irreversible tilt of their neck region and sometimes by a sustained shortening and swelling. A possible osmotic contribution to these shape changes was investigated by substituting gluconate (G) for chloride in the test solution, so as to minimize water influx, and also by changing the osmotic pressure of the extracellular solution. For comparison, similar experiments were also undertaken on cochlear outer hair cells (OHCs). Utricular and ampullar type I hair cells were more difficult to isolate than OHCs and, like them, responded to an isotonic high [KCl] solution by a sustained shortening and widening, which were found to be reversible for most cells when rinsed with the control solution. In a high [KG] solution, all OHCs showed a shortening reversible in the test solution; among the VIHCs tested, two-thirds presented a slight sustained shortening without widening and a third showed a spontaneously reversible shortening, particularly at the neck level. VIHCs exposed to a high [N-methyl-D-glucamine chloride] solution, this impermeant cation replacing K+ for control, presented only a slight sustained shortening. In response to osmotic changes of the bathing medium, both VIHCs and OHCs showed a sustained shortening or elongation (the latter to a lesser degree) for hypo- and hyperosmotic solutions, respectively. The VIHCs and OHCs that presented a reversible shortening in a high [KG] solution widened concomitantly with their shortening, but to a smaller extent compared with what was observed in a high [KCl] solution, and this diameter increase was reversible in the test solution, unlike the widening observed in a hypotonic solution. These results show that a reversible shortening occurred for some VIHCs; they also indicate the involvement of two components in the KCl-induced response: one osmotic and another potassium-dependent.

A delayed rectifier conductance in type I hair cells of the mouse utricle

1996 ◽  
Vol 76 (2) ◽  
pp. 995-1004 ◽  
Author(s):  
A. Rusch ◽  
R. A. Eatock
Keyword(s):  
Hair Cells ◽  
Time Course ◽  
Dissociation Constants ◽  
Resting Potential ◽  
Delayed Rectifier ◽  
Type I ◽  
Type Ii ◽  
Voltage Range ◽  
Average Maximum

1. Membrane currents of hair cells in acutely excised or cultured mouse utricles were recorded with the whole cell voltage-clamp method at temperatures between 23 and 36 degrees C. 2. Type I and II hair cells both had delayed rectifier conductances that activated positive to -55 mV. 3. Type I, but not type II, hair cells had an additional delayed rectifier conductance (gK,L) with an activation range that was unusually negative and variable. At 23-25 degrees C, V(1/2) values ranged from -88 to -62 mV in 57 cells. 4. gK,L was very large. At 23-25 degrees C, the average maximum chord conductance was 75 +/- 65 nS (mean +/- SD, n = 57; measured at -54 mV), or approximately 21 nS/pF of cell capacitance. 5. gK,L was highly selective for K+ over Na+ (permeability ratio PNa+/PK+:0.006), but unlike other delayed rectifiers, gK,L was significantly permeable to Cs+ (PCs+/PK+:0.31). gK,L was independent of extracellular Ca2+. 6. At -64 mV, Ba2+ and 4-aminopyridine blocked gK,L with apparent dissociation constants of 2.0 mM and 43 microM, respectively. Extracellular Cs+ (5 mM) blocked gK,L by 50% at -124 mV. Apamin (100 nM) and dendrotoxin (10 nM) has no effect. 7. The kinetic data of gK,L are consistent with a sequential gating model with at least two closed states and one open state. The slow activation kinetics (principal time constants at 23-25 degrees C:600-200 ms) had a thermal Q10 of 2.1. Inactivation (Q10:2.7) was partial at all temperatures. Deactivation followed a double-exponential time course and had a Q10 of 2.0. 8. At 23-25 degrees C, gK,L was appreciably activated at the mean resting potential of type I hair cells (-77 +/- 3.1 mV, n = 62), so that input conductances were often more than an order of magnitude larger than those of type II cells. If these conditions hold in vivo, type I cells would produce unusually small receptor potentials. Warming the cells to 36 degrees C produced parallel shifts in gK,L's activation range (0.8 +/- 0.3 mV/degrees C, n = 8), and in the resting potential (0.6 +/- 0.3 mV/degrees C, n = 4). Thus the high input conductances were not an artifact of unphysiological temperatures but remained high near body temperature. It remains possible that in vivo gK,L's activation range is less negative and input conductances are lower; the large variance in the voltage range of activation suggests that it may be subject to modulation.

Ionic Currents and Electromotility in Inner Ear Hair Cells From Humans

1998 ◽  
Vol 79 (4) ◽  
pp. 2235-2239 ◽  
Author(s):  
John S. Oghalai ◽  
Jeffrey R. Holt ◽  
Takashi Nakagawa ◽  
Thomas M. Jung ◽  
Newton J. Coker ◽  
...  
Keyword(s):  
Inner Ear ◽  
Hair Cells ◽  
Ionic Currents ◽  
Sensory Epithelium ◽  
Outer Hair Cells ◽  
Sensory Receptor ◽  
Surgical Removal ◽  
Type I ◽  
Vestibular Hair Cells ◽  
Sensory Receptor Cells

Oghalai, John S., Jeffrey R. Holt, Takashi Nakagawa, Thomas M. Jung, Newton J. Coker, Herman A. Jenkins, Ruth Anne Eatock, and William E. Brownell. Ionic currents and electromotility in inner ear hair cells from humans. J. Neurophysiol. 79: 2235–2239, 1998. The upright posture and rich vocalizations of primates place demands on their senses of balance and hearing that differ from those of other animals. There is a wealth of behavioral, psychophysical, and CNS measures characterizing these senses in primates, but no prior recordings from their inner ear sensory receptor cells. We harvested human hair cells from patients undergoing surgical removal of life-threatening brain stem tumors and measured their ionic currents and electromotile responses. The hair cells were either isolated or left in situ in their sensory epithelium and investigated using the tight-seal, whole cell technique. We recorded from both type I and type II vestibular hair cells under voltage clamp and found four voltage-dependent currents, each of which has been reported in hair cells of other animals. Cochlear outer hair cells demonstrated electromotility in response to voltage steps like that seen in rodent animal models. Our results reveal many qualitative similarities to hair cells obtained from other animals and justify continued investigations to explore quantitative differences that may be associated with normal or pathological human sensation.

Molecular characterization of an inward rectifier channel (IKir) found in avian vestibular hair cells: cloning and expression of pKir2.1

2004 ◽  
Vol 19 (2) ◽  
pp. 155-169 ◽  
Author(s):  
Manning J. Correia ◽  
Thomas G. Wood ◽  
Deborah Prusak ◽  
Tianxiang Weng ◽  
Katherine J. Rennie ◽  
...  
Keyword(s):  
Hair Cells ◽  
Cho Cells ◽  
Dwell Time ◽  
Single Channel ◽  
Cloning And Expression ◽  
Single Type ◽  
Type I ◽  
Type Ii ◽  
Vestibular Hair Cells ◽  
Inwardly Rectifying

A fast inwardly rectifying current has been observed in some of the sensory cells (hair cells) of the inner ear of several species. While the current was presumed to be an IKir current, contradictory evidence existed as to whether the cloned channel actually belonged to the Kir2.0 subfamily of potassium inward rectifiers. In this paper, we report for the first time converging evidence from electrophysiological, biochemical, immunohistochemical, and genetic studies that show that the Kir2.1 channel carries the fast inwardly rectifying currents found in pigeon vestibular hair cells. Following cytoplasm extraction from single type II and multiple pigeon vestibular hair cells, mRNA was reverse transcribed, amplified, and sequenced. The open reading frame (ORF), consisting of a 1,284-bp nucleotide sequence, showed 94, 85, and 83% identity with Kir2.1 subunit sequences from chick lens, Kir2 sequences from human heart, and a mouse macrophage cell line, respectively. Phylogenetic analyses revealed that pKir2.1 formed an immediate node with hKir2.1 but not with hKir2.2–2.4. Hair cells (type I and type II) and supporting cells in the sensory epithelium reacted positively with a Kir2.1 antibody. The whole cell current recorded in oocytes and CHO cells, transfected with pigeon hair cell Kir2.1 (pKir2.1), demonstrated blockage by Ba2+ and sensitivity to changing K+ concentration. The mean single-channel linear slope conductance in transfected CHO cells was 29 pS. The open dwell time was long (∼300 ms at −100 mV), and the closed dwell time was short (∼34 ms at −100 mV). Multistates ranging from 3–6 were noted in some single-channel responses. All of the above features have been described for other Kir2.1 channels. Current clamp studies of native pigeon vestibular hair cells illustrated possible physiological roles of the channel and showed that blockage of the channel by Ba2+ depolarized the resting membrane potential by ∼30 mV. Negative currents hyperpolarized the membrane ∼20 mV before block but ∼60 mV following block. RT-PCR studies revealed that the pKir2.1 channels found in pigeon vestibular hair cells were also present in pigeon vestibular nerve, vestibular ganglion, lens, neck muscle, brain (brain stem, cerebellum and optic tectum), liver, and heart.

Electrically Evoked Motile Responses of Mammalian Type I Vestibular Hair Cells

1992 ◽  
Vol 2 (3) ◽  
pp. 181-191
Author(s):  
Hans Peter Zenner ◽  
Günter Reuter ◽  
Shi Hong ◽  
Ulrike Zimmermann ◽  
Alfred H. Gitter
Keyword(s):  
Hair Cells ◽  
Sensory Modality ◽  
Outer Hair Cells ◽  
Type I ◽  
Image Subtraction ◽  
Low Frequencies ◽  
Vestibular Hair Cells ◽  
Mechanical Responses ◽  
Contrast Enhanced ◽  
Length Changes

Vestibular hair cells, type I and II, with membrane potentials around -64 mV were prepared from guinea pig ampullar cristae and maculae. In type I cells, current injection, application of voltage steps during membrane patch-clamping, or extracellular alternating current (ac) fields evoked fast length changes of 50 nm to 500 nm of the cell “neck”. Mechanical responses were determined by computerized video techniques with contrast-enhanced digital image subtraction (DIS) and interpeak pixel counts (IPPC) or by double photodiode measurements. These techniques allowed spatial resolutions of 300 nm, 120 nm, and 50 nm, respectively. In contrast to measurements of high-frequency movements of auditory outer hair cells (OHCs), the mechanical responses of type I VHCs were restricted to low frequencies below 85 Hz. In addition to recently reported slow motility of VHCs, the present results suggest that fast mechanical VHC responses could significantly influence macular and cupular mechanics. Isometric and isotonic variants are discussed. The observed frequency maxima gap between VHCs and OHCs is suggested to contribute to a clear separation of the auditory and the vestibular sensory modality.

Sign in / Sign up

Export Citation Format

Share Document