1,721,171 research outputs found
Minimally invasive transcochlear approach for future optogenetic manipulation of spiral ganglion neurons
No full textThe presynaptic function of mouse cochlear inner hair cells during development of hearing
No full textBefore mice start to hear at approximately postnatal day 10, their cochlear inner hair cells (IHCs) spontaneously generate Ca2+ action potentials. Therefore, immature IHCs could stimulate the auditory pathway, provided that they were already competent for transmitter release. Here, we combined patch-clamp capacitance measurements and fluorimetric [Ca2+](i) recordings to study the presynaptic function of IHCs during cochlear maturation. Ca2+-dependent exocytosis and subsequent endocytic membrane retrieval were already observed near the date of birth. Ca2+ action potentials triggered exocytosis in immature IHCs, which probably activates the auditory pathway before it becomes responsive to sound. IHCs underwent profound changes in Ca2+-channel expression and secretion during their postnatal development. Ca2+-channel expression increased toward the end of the first week, providing for large secretory responses during this period and thereafter declined to reach mature levels. The efficacy whereby Ca2+ influx triggers exocytosis increased toward maturation, such that vesicle fusion caused by a given Ca2+ current occurred faster in mature IHCs. The observed changes in Ca2+-channel expression and synaptic efficacy probably reflected the ongoing synaptogenesis in IHCs that had been described previously in morphological studies
Minimalinvasiver transcochleärer Zugang für eine zukünftige optogenetische Manipulation von Spiralganglienneuronen
No full textThe presynaptic function of mouse cochlear inner hair cells during development of hearing
No full textBefore mice start to hear at approximately postnatal day 10, their cochlear inner hair cells (IHCs) spontaneously generate Ca2+ action potentials. Therefore, immature IHCs could stimulate the auditory pathway, provided that they were already competent for transmitter release. Here, we combined patch-clamp capacitance measurements and fluorimetric [Ca2+](i) recordings to study the presynaptic function of IHCs during cochlear maturation. Ca2+-dependent exocytosis and subsequent endocytic membrane retrieval were already observed near the date of birth. Ca2+ action potentials triggered exocytosis in immature IHCs, which probably activates the auditory pathway before it becomes responsive to sound. IHCs underwent profound changes in Ca2+-channel expression and secretion during their postnatal development. Ca2+-channel expression increased toward the end of the first week, providing for large secretory responses during this period and thereafter declined to reach mature levels. The efficacy whereby Ca2+ influx triggers exocytosis increased toward maturation, such that vesicle fusion caused by a given Ca2+ current occurred faster in mature IHCs. The observed changes in Ca2+-channel expression and synaptic efficacy probably reflected the ongoing synaptogenesis in IHCs that had been described previously in morphological studies
Kinetics of exocytosis and endocytosis at the cochlear inner hair cell afferent synapse of the mouse.
No full textHearing in mammals relies on the highly synchronous synaptic transfer between cochlear inner hair cells (IHCs) and the auditory nerve. We studied the presynaptic function of single mouse IHCs by monitoring membrane capacitance changes and voltage-gated Ca2+ currents, Exocytosis initially occurred at a high rate but then slowed down within a few milliseconds, despite nearly constant Ca2+ influx. We interpret the observed secretory depression as depletion of a readily releasable pool (RRP) of about 280 vesicles. These vesicles are probably docked close to Ca2+ channels at the ribbon-type active zones of the IHCs, Continued depolarization evoked slower exocytosis occurring at a nearly constant rate for at least 1 s and depending on "long-distance" Ca2+ signaling. Refilling of the RRP after depletion followed a biphasic time course and was faster than endocytosis. RRP depletion is discussed as a mechanism for fast auditory adaptation
Cell membrane lipids affect the mechano-electrical transduction channel. PIP2 (phosphatidylinositol-4,5-bisphosphat) specifically modulating single channel conductance and ion selectivity
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