We report the cloning and characterization of rat α10, a previously unidentified member nicotinic acetylcholine receptor (nAChR) subunit gene family. The protein encoded by α10 nAChR is most similar to α9 nAChR, both genes are transcribed in adult mechanosensory hair cells. Injection Xenopus laevis oocytes with cRNA alone or pairwise combinations either α2-α6 β2-β4 cRNAs yielded no detectable ACh-gated currents. However, coinjection resulted appearance an unusual subtype. Compared homomeric...

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...

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...

Although homomeric channels assembled from the alpha9 nicotinic acetylcholine receptor (nAChR) subunit are functional in vitro, electrophysiological, anatomical, and molecular data suggest that native cholinergic olivocochlear function is mediated via heteromeric nAChRs composed of both alpha10 subunits. To gain insight into vivo, we examined olivo cochlear innervation null-mutant mice. Electrophysiological recordings postnatal (P) days P8-9 inner hair cells revealed ACh-gated currents...

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...

In the present study, we provide evidence that α9 nicotinic acetylcholine receptor (nAChR) shares pharmacological properties with members of Cys-loop family receptors. Thus, type A γ-aminobutyric acid antagonist bicuculline, glycinergic strychnine, and 3 serotonin ICS-205,930 block ACh-evoked currents in α9-injected <i>Xenopus laevis</i> oocytes following rank order potency: strychnine &gt; bicuculline. Block by antagonists was reflected an increase (ACh) EC₅₀ value, no changes...

The α9 and α10 nicotinic cholinergic subunits assemble to form the receptor that mediates synaptic transmission between efferent olivocochlear fibers hair cells of cochlea. They are latest vertebrate (nAChR) have been cloned, their identification has established a distant early divergent branch within nAChR gene family. subunit serves as “structural” component leading heteromeric α9α10 nAChRs with distinct properties. We now probed stoichiometry recombinant expressed in Xenopus oocytes. made...

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...

Cochlear outer hair cells (OHCs) are electromotile and implicated in amplification of responses to sound that enhance sensitivity frequency tuning. They send afferent information through glutamatergic synapses onto type II spiral ganglion neurons (SGNs). These weaker than those from cochlear inner I SGN, suggesting SGNs respond only intense levels. OHCs also receive efferent innervation medial olivocochlear (MOC) neurons. MOC cholinergic yet inhibit due the functional coupling alpha9/alpha10...

1. The involvement of the different types voltage‐dependent calcium channels (VDCCs) in synaptic transmission at mature and newly formed mammalian neuromuscular junction was studied by evaluating effects L‐, P/Q‐ N‐type VDCC antagonists on transmitter release normal reinnervating levator auris preparations adult mice. 2. Nerve‐evoked blocked omega‐agatoxin IVA (omega‐AgaIVA), a P/Q‐type blocker, both endplates (100 nM omega‐AgaIVA caused &gt; 90% inhibition). antagonist omega‐conotoxin GVIA...

In the mammalian inner ear, gain control of auditory inputs is exerted by medial olivocochlear (MOC) neurons that innervate cochlear outer hair cells (OHCs). OHCs mechanically amplify incoming sound waves virtue their electromotile properties while MOC system reduces inhibiting OHC function. How this process orchestrated at synaptic level remains unknown. present study, firing was evoked electrical stimulation in an isolated mouse preparation, postsynaptic responses were monitored whole-cell...

The α9 and α10 cholinergic nicotinic receptor subunits assemble to form the that mediates efferent inhibition of hair cell function within auditory sensory organ, a mechanism thought modulate dynamic range hearing. In contrast all receptors, which serve excitatory neurotransmission, activation α9α10 produces hyperpolarization cells. An evolutionary analysis has shown subunit exhibits signatures positive selection only along mammalian lineage, strongly suggesting acquisition unique function....

Nicotinic acetylcholine receptors are a family of ligand-gated nonselective cationic channels that participate in fundamental physiological processes at both the central and peripheral nervous system. The extent calcium entry through ion defines their distinct functions. α9α10 nicotinic cholinergic receptor, expressed cochlear hair cells, is peculiar member as it shows differences permeability across species. In particular, mammalian among which exhibit highest selectivity. This acquired...

1. The effects of the calcium channel blockers, funnel‐web spider toxin (FTX), omega‐agatoxin IVA (omega‐Aga IVA) and omega‐conotoxin GVIA (omega‐CgTX), were tested on transmitter release presynaptic currents in frog motor nerve endings. 2. Evoked was blocked by FTX (IC50 = 0.02 microliter ml‐1) omega‐CgTX (1 microM) but not affected omega‐Aga (0.5 microM). When (0.1 assayed spontaneous either normal Ringer solution or low Ca(2+)‐high Mg2+ solution, it found to affect miniature endplate...

In the present work, we characterized effects of serotonin type 3 receptor ligands on recombinant and native α9α10-containing nicotinic acetylcholine receptors (nAChRs). Our results indicate that α9α10 nAChR shares striking pharmacological properties with 5-HT₃ ligand-gated ion channels. Thus, antagonists block ACh-evoked currents in α9α10-injected <i>Xenopus laevis</i> oocytes a rank order potency tropisetron (IC₅₀, 70.1 ± 0.9 nM) &gt; ondansetron 0.6 0.1 μM) = MDL...

In this study, we report the effects of quinoline derivatives quinine, its optical isomer quinidine, and chloroquine on α9α10-containing nicotinic acetylcholine receptors (nAChRs). The compounds blocked (ACh)-evoked responses in α9α10-injected <i>Xenopus laevis</i> oocytes a concentration-dependent manner, with rank order potency (IC₅₀ = 0.39 μM) &gt; quinine 0.97 ∼ quinidine 1.37 μM). Moreover, ACh-evoked rat cochlear inner hair cells an IC₅₀ value 0.13 μM, which is...

In the mammalian auditory system, synapse between efferent olivocochlear (OC) neurons and sensory cochlear hair cells is cholinergic, fast, inhibitory. This mediated by nicotinic α9α10 receptor coupled to activation of SK2 Ca 2+ -activated K + channels that hyperpolarize cell. So far, ion support and/or modulate neurotransmitter release from OC terminals remain unknown. To identify these channels, we used an isolated mouse preparation monitored transmitter synaptic in inner (IHCs) voltage...

The synapse between olivocochlear (OC) neurons and cochlear mechanosensory hair cells is cholinergic, fast, inhibitory. inhibitory sign of this cholinergic accounted for by the activation Ca 2+ -permeable postsynaptic α9α10 nicotinic receptors coupled to opening hyperpolarizing -activated small-conductance type 2 (SK2)K + channels. Acetylcholine (ACh) release at supported both P/Q- N-type voltage-gated calcium channels (VGCCs). Although OC an abundant GABA innervation present along mammalian...

Voltage-dependent Ca 2+ channels are a major pathway for entry in neurons. We have studied the electrophysiological, pharmacological, and molecular properties of voltage-gated motoneurons rat facial nucleus slices brainstem. Most express both low voltage-activated (LVA) high (HVA) channel currents. The HVA current is composed number pharmacologically separable components, including 30% N-type ∼5% L-type. Despite dominating role P-type transmitter release at motoneuron terminals described...

The effects of the voltage‐dependent calcium channel (VDCC) blockers ω‐agatoxin IVA (ω‐AgaIVA), ω‐conotoxin GVIA (ω‐CgTx), MVIIC (ω‐MVIIC) and MVIID (ω‐MVIID) were evaluated on transmitter release in mouse diaphragm preparation. ω‐AgaIVA ω‐MVIIC also perineurial calcium‐dependent potassium currents, I Ca K(Ca) , respectively, levator auris P‐ Q‐type VDCC blocker (100 n M ) Q‐ N‐type (1 μ ω‐MVIID (3 strongly reduced (&gt;80–90% blockade) whereas selective ω‐CgTx (5 was ineffective. process...