Neural Circuit Development in the Mammalian Cochlea

Physiology ◽  
2012 ◽  
Vol 27 (2) ◽  
pp. 100-112 ◽  
Author(s):  
A. V. Bulankina ◽  
T. Moser
Keyword(s):  
Auditory System ◽  
Neural Circuit ◽  
Organ Of Corti ◽  
Sensory Epithelium ◽  
Top Down ◽  
Cochlear Function ◽  
Mouse Organ ◽  
Circuit Development ◽  
Auditory Signals

The organ of Corti, the sensory epithelium of the mammalian auditory system, uses afferent and efferent synapses for encoding auditory signals and top-down modulation of cochlear function. During development, the final precisely ordered sensorineural circuit is established following excessive formation of afferent and efferent synapses and subsequent refinement. Here, we review the development of innervation of the mouse organ of Corti and its regulation.

A technique for protecting delicate specimens during processing

1989 ◽  
Vol 47 ◽  
pp. 982-983
Author(s):  
R.J. Mount ◽  
R.V. Harrison
Keyword(s):  
Basilar Membrane ◽  
Low Cost ◽  
Organ Of Corti ◽  
Region Of Interest ◽  
Sensory Epithelium ◽  
Physical Damage ◽  
Air Drying ◽  
Specimen Handling ◽  
Two Component

The sensory end organ of the ear, the organ of Corti, rests on a thin basilar membrane which lies between the bone of the central modiolus and the bony wall of the cochlea. In vivo, the organ of Corti is protected by the bony wall which totally surrounds it. In order to examine the sensory epithelium by scanning electron microscopy it is necessary to dissect away the protective bone and expose the region of interest (Fig. 1). This leaves the fragile organ of Corti susceptible to physical damage during subsequent handling. In our laboratory cochlear specimens, after dissection, are routinely prepared by the O-T- O-T-O technique, critical point dried and then lightly sputter coated with gold. This processing involves considerable specimen handling including several hours on a rotator during which the organ of Corti is at risk of being physically damaged. The following procedure uses low cost, readily available materials to hold the specimen during processing ,preventing physical damage while allowing an unhindered exchange of fluids.Following fixation, the cochlea is dehydrated to 70% ethanol then dissected under ethanol to prevent air drying. The holder is prepared by punching a hole in the flexible snap cap of a Wheaton vial with a paper hole punch. A small amount of two component epoxy putty is well mixed then pushed through the hole in the cap. The putty on the inner cap is formed into a “cup” to hold the specimen (Fig. 2), the putty on the outside is smoothed into a “button” to give good attachment even when the cap is flexed during handling (Fig. 3). The cap is submerged in the 70% ethanol, the bone at the base of the cochlea is seated into the cup and the sides of the cup squeezed with forceps to grip it (Fig.4). Several types of epoxy putty have been tried, most are either soluble in ethanol to some degree or do not set in ethanol. The only putty we find successful is “DUROtm MASTERMENDtm Epoxy Extra Strength Ribbon” (Loctite Corp., Cleveland, Ohio), this is a blue and yellow ribbon which is kneaded to form a green putty, it is available at many hardware stores.

scholarly journals Molecular Mechanisms of Neural Circuit Development and Regeneration

2021 ◽  
Vol 22 (9) ◽  
pp. 4593
Author(s):  
Lieve Moons ◽  
Lies De Groef
Keyword(s):  
Human Brain ◽  
Molecular Mechanisms ◽  
Neural Circuit ◽  
Circuit Development

The human brain contains 86 billion neurons [...]

scholarly journals Thyroid Hormone Deficiency Before the Onset of Hearing Causes Irreversible Damage to Peripheral and Central Auditory Systems

2000 ◽  
Vol 83 (5) ◽  
pp. 3101-3112 ◽  
Author(s):  
Marlies Knipper ◽  
Christoph Zinn ◽  
Hannes Maier ◽  
Mark Praetorius ◽  
Karin Rohbock ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Auditory System ◽  
Critical Time ◽  
Organ Of Corti ◽  
Thyroid Gland Function ◽  
Distortion Product ◽  
Fetal Thyroid ◽  
Gland Function ◽  
Dependent Processes

Both a genetic or acquired neonatal thyroid hormone (TH) deficiency may result in a profound mental disability that is often accompanied by deafness. The existence of various TH-sensitive periods during inner ear development and general success of delayed, corrective TH treatment was investigated by treating pregnant and lactating rats with the goitrogen methimazole (MMI). We observed that for the establishment of normal hearing ability, maternal TH, before fetal thyroid gland function on estrus days 17–18, is obviously not required. Within a crucial time between the onset of fetal thyroid gland function and the onset of hearing at postnatal day 12 ( P12), any postponement in the rise of TH-plasma levels, as can be brought about by treating lactating mothers with MMI, leads to permanent hearing defects of the adult offspring. The severity of hearing defects that were measured in 3- to 9-mo-old offspring could be increased with each additional day of TH deficiency during this critical period. Unexpectedly, the active cochlear process, assayed by distortion product otoacoustic emissions (DPOAE) measurements, and speed of auditory brain stem responses, which both until now were not thought to be controlled by TH, proved to be TH-dependent processes that were damaged by a delay of TH supply within this critical time. In contrast, no significant differences in the gross morphology and innervation of the organ of Corti or myelin gene expression in the auditory system, detected as myelin basic protein (MBP) and proteolipid protein (PLP) mRNA using Northern blot approach, were observed when TH supply was delayed for few days. These classical TH-dependent processes, however, were damaged when TH supply was delayed for several weeks. These surprising results may suggest the existence of different TH-dependent processes in the auditory system: those that respond to corrective TH supply (e.g., innervation and morphogenesis of the organ of Corti) and those that do not, but require T3 activity during a very tight time window (e.g., active cochlear process, central processes).

Gene Expression Profile of the Mouse Organ of Corti at the Onset of Hearing

Genomics ◽  
2004 ◽  
Vol 83 (6) ◽  
pp. 1000-1011 ◽  
Author(s):  
Celine Pompeia ◽  
Belen Hurle ◽  
Inna A. Belyantseva ◽  
Konrad Noben-Trauth ◽  
Kirk Beisel ◽  
...  
Keyword(s):  
Gene Expression ◽  
Gene Expression Profile ◽  
Expression Profile ◽  
Organ Of Corti ◽  
Mouse Organ

Damage of the Auditory System Associated with Acute Blast Trauma

1989 ◽  
Vol 98 (5_suppl) ◽  
pp. 23-34 ◽  
Author(s):  
Michele Roberto ◽  
Roger P. Hamernik ◽  
George A. Turrentine
Keyword(s):  
Auditory System ◽  
Sound Pressure ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
Blast Waves ◽  
Mechanical Fracture ◽  
Sound Pressure Levels ◽  
Temporal Bones ◽  
Blast Trauma ◽  
The Impact

This paper reviews the results of several studies on the effects of blast wave exposure on the auditory system of the chinchilla, the pig, and the sheep. The chinchillas were exposed at peak sound pressure levels of approximately 160 dB under well-controlled laboratory conditions. A modified shock tube was used to generate the blast waves. The pigs and sheep were exposed under field conditions in an instrumented hard-walled enclosure. Blast trauma was induced by the impact of a single explosive projectile. The peak sound pressure levels varied between 178 and 209 dB. All animals were killed immediately following exposure, and their temporal bones were removed for fixation and histologic analysis using light microscopy and scanning electron microscopy. Middle ears were examined visually for damage to the conductive system. There were well-defined differences in susceptibility to acoustic trauma among species. However, common findings in each species were the acute mechanical fracture and separation of the organ of Corti from the basilar membrane, and tympanic membrane and ossicular failure.

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