Synaptic activity of auditory and vestibular hair cells

·--------------------------------------------------------------------------------------------------------············xiv CHAPTER 1: The inner ear and hair cell resonant frequency Introduction: Sensory organs of the inner ear and innervation ..... ------------------------------·--------·1 Hair cell shape and innervation of the cochlea and sacculus ......................... 2 Frequency detection in the cochlea and sacculus __________________________________________ .4 Resonant frequency in non-mammalian hair cells ........................................... 5 CHAPTER II: The afferent synapse Introduction: Afferent synapse architecture ............... ---------------------------------------------·--------------·9 Exocytosis at the afferent synapse __________________________________________________________________ .11 Vesicle replenishment ..... -----------------------------------------------------------·--------------------···16 Results: Calcium entry sites in hair cells ------------------------------------------------------------------------·18 CtBP staining of hair cell dense bodies .......................................................... J9 Voltage-gated inward current and exocytosis .................................................. 20 Spontaneous fluorescence and membrane voltage oscillation at rest __________ 20 Fluo-3 fluorescence transients .......................................................................... 21 A fast RRP observed in hair cells ...................................................................... 21 Spontaneous release of FM1-43 dye observed with TIRF microscopy ________ .22 Possible fusion of a small, synaptic vesicle ...................................................... 23 Varied vesicle diameters at the dense body in electron micrographs ___________ 24 Dense bodies at presumed afferent synapses in electron micrographs _______ 25 Discussion: Identification of the afferent synapse in hair cells ............................................ 26 Voltage-gated calcium channels in bullfrog saccular hair cells ...................... 27 Membrane voltage oscillation in bullfrog saccular hair cells ........................... 28 Fluo dye fluorescence transients imaged with TIRF ........................................ 28 Ready-releasable poo1 ....................................................................................... 29 The estimated RRP size exceeds the dense body's complement of vesicles in bullfrog saccular hair cells .................................................. 31 Physiologically-relevant stimulation and the RRP ___________________________________________ 33 Spontaneous vesicle fusion in bullfrog saccular hair cells ______________________________ 33 Endosome size and multi-vesicular release ..................................................... 34 CHAPTER Ill: The efferent synapse Introduction: Efferent synapse activity __ .................................................................................. 36 Cholinergic efferent effects on sensory detection ............................................ 37 Ionic activity at the cholinergic efferent synapse .............................................. 37 Nicotinic ACh receptors ...................................................................................... 38 SK channels ........................................................................................................ 39