Efferent feedback onto sensory organs provides a means to modulate input the central nervous system. In developing mammalian cochlea, inner hair cells are transiently innervated by efferent fibers, even before function begins. Here, we show that neonatal inhibited cholinergic synaptic onset of hearing. The currents, as well cell's response acetylcholine, mediated nicotinic (alpha9-containing) receptor and result in activation small-conductance calcium-dependent potassium channels.

1. Potassium currents were characterized in tall hair cells of the chick's cochlea. Outward potassium found to flow through two distinct classes channels. 2. Individual isolated from 200 microns long segments apical half Whole‐cell voltage‐clamp and current‐clamp recordings made these cells. 3. Voltage responses injected current ranged high‐frequency (100‐250 Hz) oscillations some cells, slowly repetitive Ca2+ action potentials or slow (5‐20 others. 4. Ionic recorded voltage clamp also...

Significance Painfully loud sound causes protective or withdrawal responses, rather than continued listening. This differential behavior invites comparison with somatic pain responses driven by the anatomically distinct subset of small-diameter, unmyelinated afferents—C fibers. Like C fibers, type II cochlear afferents differ in size, number, and innervation pattern from I that encode sound. Here, we show are excited during tissue damage part algogenic cytoplasmic metabolite adenosine...

Cochlear frequency selectivity in lower vertebrates arises part from electrical tuning intrinsic to the sensory hair cells. The resonant is determined largely by gating kinetics of calcium-activated potassium (BK) channels encoded slo gene. Alternative splicing chick cochlea generated kinetically distinct BK channels. Combination with accessory β subunits slowed α splice variants but preserved relative differences between them. In situ hybridization showed that subunit preferentially...

In the mature cochlea, inner hair cells (IHCs) transduce acoustic signals into receptor potentials, communicating to brain by synaptic contacts with afferent fibers. Before onset of hearing, a transient efferent innervation is found on IHCs, mediated nicotinic cholinergic that may contain both α9 and α10 subunits. Calcium influx through activates calcium-dependent (SK2-containing) potassium channels. This inhibitory synapse thought disappear after hearing [after postnatal day 12 (P12)]. We...

Ca V 1.3 channels comprise a vital subdivision of L-type 2+ channels: mediate neurotransmitter release from auditory inner hair cells (IHCs), pancreatic insulin secretion, and cardiac pacemaking. Fitting with these diverse roles, exhibit striking variability in their inactivation by intracellular . IHCs show generally weak-to-absent -dependent (CDI), potentially permitting audition sustained sounds. In contrast, the strong CDI seen elsewhere likely provides critical negative feedback. Here,...

The central nervous system provides feedback regulation at several points within the peripheral auditory apparatus. One component of that is inhibition cochlear hair cells by release acetylcholine (ACh) from efferent brainstem neurons. mechanism cell inhibition, and character presumed cholinergic receptor, however, have eluded understanding. Both nicotinic muscarinic, as well some non-cholinergic ligands can affect action. We made whole-cell, tight-seal recordings short (outer) isolated...

Intracellular recordings were made from turtle cochlear hair cells in order to examine the properties of post‐synaptic potentials evoked by electrical stimulation efferent axons. Single shocks efferents generated a cell membrane hyperpolarization with an average amplitude generally less than 1 mV and lasting for about 100 ms. With short trains shocks, size potential grew markedly maximum 20‐30 mV. The interaction between pairs separated varying interval was studied. For 4 ms, response second...

1. Individual, identified neurones, dissected from the central nervous system of leech and maintained in culture for several weeks, sprouted processes formed synaptic connexions.2. The action potentials isolated touch (T), pressure (P), nociceptive (N) cells Retzius resembled those their counterparts situ, enabling them to be recognized unambiguously. Their input resistances were approximately 4 times greater than corresponding within animal. In T, P N trains impulses followed by a...

The transduction of sound in the auditory periphery, cochlea, is inhibited by efferent cholinergic neurons projecting from brainstem and synapsing directly on mechanosensory hair cells. One fundamental question neuroscience what role(s) this feedback plays our ability to hear. In present study, we have engineered a genetically modified mouse model which magnitude duration effects are increased, assess consequences manipulation cochlear function. We generated Chrna9L9'T line knockin mice with...

1. Chemical synaptic transmission develops between individual identified neurones dissected from leech ganglia and maintained in culture. Impulses Retzius cells give rise to hyperpolarizing potentials pressure (P) sensory cells. In suitable medium the develop by 3 days can be observed for more than weeks. 2. The occur after a delay, exhibit facilitation depression are reversed hyperpolarization. blocking effects of reduced calcium raised magnesium concentrations bathing fluid provide...

Cochlear hair cells are inhibited by cholinergic efferent neurons. The acetylcholine (ACh) receptor of the cell is a ligand-gated cation channel through which calcium enters to activate potassium channels and hyperpolarize cell. It has been proposed that calcium-induced release (CICR) from near-membrane postsynaptic store supplements this process. Here, we demonstrate expression type I ryanodine receptors in outer apical turn rat cochlea. Consistent with finding, other store-active compounds...

Rapid transmitter release at synapses depends on the close proximity of voltage-gated calcium channels (VGCCs). In mechanosensory hair cells vertebrate inner ear, dihydropyridine-sensitive VGCCs may be preferentially expressed sites to support release. this hypothesis we have found that whole-cell current through covaried with afferent innervation density among chick's basilar papilla (the avian analog mammalian Organ Corti). The size as well number presynaptic dense bodies (PDBs) around...

Intracellular recordings were made from turtle cochlear hair cells in order to study the changes their tuning properties resulting electrical stimulation of efferent axons. Efferent caused a reduction amplitude receptor potential at cell's most sensitive or characteristic frequency, an increased frequencies more than octave below and no change very high frequencies. These differential effects resulted broadening each curve, which, during maximal degenerated sharply tuned resonance critically...

Before the onset of hearing, a transient efferent innervation is found on inner hair cells (IHCs). This synapse inhibitory and mediated by nicotinic cholinergic receptor (nAChR) probably formed α9 α10 subunits. We analysed pharmacological biophysical characteristics native nAChR using whole‐cell recordings from IHCs in acutely excised apical turns rat organ Corti. Nicotine did not activate but rather blocked acetylcholine (ACh)‐evoked currents with an IC 50 1 ± 0.1 μ m . Antagonists...