Channel Gating Research Articles

Trivalent anions as probes of the CFTR channel pore.

The cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel uses positively charged amino-acid side-chains to form binding sites for permeating anions. These binding sites have been investigated experimentally using a number of anionic probes. Mutations that alter the distribution of positive and negative charges within the pore have differential effects on the binding of monovalent versus divalent anions. This study uses patch clamp recording from wild-type and pore-mutant forms of CFTR to investigate small trivalent anions (Co(NO2)63-, Co(CN)3- and IrCl63-) as potential probes of anion binding sites. These anions caused weak block of Cl- permeation in wild-type CFTR (Kd ≥ 700 μM) when applied to the intracellular side of the membrane. Mutations that increase the density of positive charge within the pore (E92Q, I344K, S1141K) increased the binding affinity of these anions 80-280-fold, and also greatly increased the voltage-dependence of block, consistent with fixed charges in the pore affecting monovalent : multivalent anion selectivity. However, high-affinity pore block by Co(NO2)63-apparently did not alter channel gating, a hallmark of high-affinity binding of divalent Pt(NO2)42- ions within the pore. This work increases the arsenal of probes available to investigate anion binding sites within Cl- channel pores.

A Novel Single Isolation Channel Gate Driver with Bi-Directional-Signal and Forward-Power Transmission

A Novel Single Isolation Channel Gate Driver with Bi-Directional-Signal and Forward-Power Transmission

Chapter 5 - Congenital myasthenic syndromes

The neuromuscular junction is a prototypic synapse that has been extensively studied and provides a model for smaller and less accessible central synapses. Central to transmission at the neuromuscular synapse is the muscle acetylcholine receptor cation channel. Studies of the genetic disorders affecting the neuromuscular junction, termed congenital myasthenic syndromes, have illustrated how impaired signal transmission may be caused by a variety of mutations both within the ion channel itself and by the context of the ion channel within the synapse. Thus, multiple pathogenic mutations are also identified in proteins affecting the clustering, location, and density of the receptor within the overall synaptic structure. Disease severity ranges from death in childhood to mild disability throughout life. In addition, in utero, fetal akinesia due to impaired neuromuscular transmission may cause developmental abnormalities. Early studies identified mutations in the genes encoding the acetylcholine receptor subunits that impair ion channel gating or reduce the number of endplate receptors or a combination of the two, giving rise to "slow channel," "fast channel," or deficiency syndromes. Subsequently, it became clear that myasthenic syndromes also stem from mutations in proteins involved in neurotransmitter release, the formation and maintenance of the neuromuscular synapse, or glycosylation. This chapter describes the patient phenotypes, the diverse range of molecular mechanisms for synaptic dysfunction, and the corresponding therapeutic strategies, including drug combinations, that can be tailored to the many subtypes.

MULTIFRACTAL CHARACTERISTICS OF THE MITOCHONDRIAL BK CHANNEL ACTIVITY IN THE PRESENCE OF THE CHANNEL-ACTIVATING FLAVONOIDS

Over the years, the (multi)fractal nature of signals describing the activity of ion channels has been observed both at the level of single-channel currents and the temporal scaling of the corresponding sojourns in conducting and non-conducting states. The recognized nonlinear and self-similar properties were interpreted regarding the underlying channel gating machinery. Nevertheless, the literature lacks in (multi)fractal description of the biochemical stimulation of ion channels. Therefore, in this work, we provide a multifractal description of the effects exerted by two different flavonoids — naringenin (Nar) and quercetin (Que) — being the regulators of the large-conductance voltage- and Ca[Formula: see text]-activated K[Formula: see text] channels from the inner mitochondrial membrane (mitoBK). Toward this aim, the focus-based multifractal detrended fluctuation analysis (MFDFA) was applied to the patch-clamp data obtained in the presence of Nar and Que in micromolar concentrations and the corresponding controls. Our results show that mitoBK channel activity has well-pronounced multifractal characteristics and long-range memory (measured by the generalized Hurst exponent) under biochemical stimulation by Nar and Que and in the absence of these substances. The spectral properties significantly change after the randomization of the analyzed series. Therefore, multifractality is an inherent feature of the mitoBK channel currents, which stems from their statistical distribution and temporal organization. Both flavonoids have similar structures and exert channel-activating effects, but they differently affect the parameters of the multifractal spectra of the corresponding patch-clamp signals. Coordination of Que leads to more prominent changes in signal complexity than Nar at membrane hyper- and depolarization. It suggests that this flavonoid has a stronger impact on the conformational dynamics of the mitoBK channels in comparison with naringenin.

A bubble model for the gating of Kv channels

Abstract Voltage-gated K$_{\mathrm{v}}$ channels play fundamental roles in many biological processes, such as the generation of the action potential. The gating mechanism of K$_{\mathrm{v}}$ channels is characterized experimentally by single-channel recordings and ensemble properties of the channel currents. In this work, we propose a bubble model coupled with a Poisson–Nernst–Planck (PNP) system to capture the key characteristics, particularly the delay in the opening of channels. The coupled PNP system is solved numerically by a finite-difference method and the solution is compared with an analytical approximation. We hypothesize that the stochastic behaviour of the gating phenomenon is due to randomness of the bubble and channel sizes. The predicted ensemble average of the currents under various applied voltage across the channels is consistent with experimental observations, and the Cole–Moore delay is captured by varying the holding potential.

Trapping Charge Mechanism in Hv1 Channels (CiHv1).

The majority of voltage-gated ion channels contain a defined voltage-sensing domain and a pore domain composed of highly conserved amino acid residues that confer electrical excitability via electromechanical coupling. In this sense, the voltage-gated proton channel (Hv1) is a unique protein in that voltage-sensing, proton permeation and pH-dependent modulation involve the same structural region. In fact, these processes synergistically work in concert, and it is difficult to separate them. To investigate the process of Hv1 voltage sensor trapping, we follow voltage-sensor movements directly by leveraging mutations that enable the measurement of Hv1 channel gating currents. We uncover that the process of voltage sensor displacement is due to two driving forces. The first reveals that mutations in the selectivity filter (D160) located in the S1 transmembrane interact with the voltage sensor. More hydrophobic amino acids increase the energy barrier for voltage sensor activation. On the other hand, the effect of positive charges near position 264 promotes the formation of salt bridges between the arginines of the voltage sensor domain, achieving a stable conformation over time. Our results suggest that the activation of the Hv1 voltage sensor is governed by electrostatic-hydrophobic interactions, and S4 arginines, N264 and selectivity filter (D160) are essential in the Ciona-Hv1 to understand the trapping of the voltage sensor.

Impact of Nanowire Radius and Channel Thickness with High-k Gate Dielectric in GAA-JLT

As the transistor’s size becomes smaller, degradation in the short-channel effects (SCEs) becomes more apparent. This leads to research work on multi-gate transistors such as the Fin-Field Effect Transistor (FinFET) and Gate-All-Around (GAA) transistor, where the 3D architecture have been shown to have superior performance as compared to conventional planar transistor. Transistor without junctions (JLT) which realizes a single type of doping has also been gaining popularity for biosensor applications due to its superior electrostatic performances in terms of Drain-Induced Barrier Lowering (DIBL), off-state leakage current (Ioff) and Subthreshold Slope (SS). In this work, the impact of changes in parameters such as the gate oxide material, nanowire radius and channel thickness toward the performance of a Gate-all-around JLT (GAA-JLT) have been studied using TCAD simulator. It was found that smaller nanowire radius and thicker channel produces lower DIBL, Ioff and SS, with the use of HfO2 as gate oxide materials shows better results than Si3N4. Meanwhile, the impact of parameters variations seemed to be negligible on the on-state current (Ion). The outcome of this work can be used as a basis to understand the impact of structural parameters variations towards the performance of a more complex GAA-JLT structure.

3-Terminal Igzo FET Based 2T0C DRAM Combined Bit-Line Structure

The IGZO (InGaZnO)-based two-transistor zero-capacitor(2T0C) DRAM has attracted much attention as an alternative memory to overcome the scale-down limit of current 1T1C DRAM due to its low power consumption and monolithic 3D stacking capability. In particular, its low power consumption and the feasibility of low temperature process make it highly implementable for 3D DRAM. For operating the 2T0C DRAM, four metal lines are necessary, i.e., write word line and write bit line (WBL) for operating write transistor (WTR), and read word line and read bit line (RBL) for operating read transistor (RTR).In this study, we propose a 3-terminal 2T0C DRAM to enhance its memory characteristics, where RBL was combined with WBL, enabling 2T0C memory operation with only three metal lines as shown in Fig. 1(b). In addition, we investigated the dependency of retenetion time of the proposed 2T0C DRAM on channel length. In particular we evaluated the dependency of the sneak current of 2T0C DRAM on off-current of transistor. For the fabrication of 3-terminal IGZO 2T0C DRAM, a top gate IGZO transistor was fabricated using RF sputtering and two transistors were connected by storage node and bit line bridge as shown in Fig. 1(d).The storage node was formed by connecting the gate of RTR to drain of WTR. And source electrodes of both transistors were coupled. To determine the voltage values for memory operation, the transfer curve of each transistor was characterized and the threshold voltages for both RTR and WTR were around 1 V. The write and read voltages were set to 3 and 2 V, respectively. The retention time was measured by performing periodic read operations after writing and measuring the RTR currents. In addition, the retention time of transistors for varying channel length and gate capacitance was characterized. The retention time was defined as the time to be taken for decreasing the currents by 90 %. Furthermore, the disturbance of 2T0C DRAM with 2x2 array structure was investigated. The RTR currents of selected cells were measured depending on the memory state of adjacent cells.It was found that the retention times of transistors with 10- and 100-um RTR channel lengths were approximately 15 and 30 seconds, respectively. It was observed that the memory state was not changed from “0“ to “1“ by disturbant currents, but, RTR currents of “0“ state cell increased slightly when an adjacent cell was turned on. However, as shown in Fig.1(i) and (j), when off-currents of transistor of 2T0C DRAM decreased from 20 nA to 200 pA, it was confirmed the sneak current of 2T0C decreased. Finally, several technical apporaches how to suppress the disturbant currents will be presented in detail. Acknowledgement This research was supported by BrainKorea21 Four. Figure 1

Deciphering the Biophysical Properties of Ion Channel Gating Pores by Coumarin-Benzodiazepine Hybrid Derivatives: Selective AMPA Receptor Antagonists.

In the 1980s, the identification of specific pharmacological antagonists played a crucial role in enhancing our comprehension of the physiological mechanisms associated with α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors (AMPARs). The primary objective of this investigation was to identify specific AMPA receptor antagonists, namely 2,3-benzodiazepines, that function as negative allosteric modulators (NAMs) at distinct locations apart from the glutamate recognition site. These compounds have exhibited a diverse array of anticonvulsant properties. In order to conduct a more comprehensive investigation, the study utilized whole-cell patch-clamp electrophysiology to analyze the inhibitory effect and selectivity of benzodiazepine derivatives that incorporate coumarin rings in relation to AMPA receptors. The study's main objective was to acquire knowledge about the relationship between the structure and activity of the compound and comprehend the potential effects of altering the side chains on negative allosteric modulation. The investigation provided crucial insights into the interaction between eight CD compounds and AMPA receptor subunits. Although all compounds demonstrated effective blockade, CD8 demonstrated the greatest potency and selectivity towards AMPA receptor subunits. The deactivation and desensitization rates were significantly influenced by CD8, CD6, and CD5, distinguishing them from the remaining five chemicals. The differences in binding and inhibition of AMPA receptor subunits can be attributed to structural discrepancies among the compounds. The carboxyl group of CD8, situated at the para position of the phenyl ring, substantially influenced the augmentation of AMPA receptor affinity. The findings of this study highlight the potential of pharmaceutical compounds that specifically target AMPA receptors to facilitate negative allosteric modulation.

Short and long-range correlations in single-channel currents from inwardly rectifying K[formula omitted] channels

Ion channels mediate the transport of ions through the cell membrane and are involved in key processes such as muscle contraction, nerve excitability and hormone secretion. For decades, the main focus of the standard techniques for the analysis and modeling of single-channel currents has been to characterize the gating of ionic channels by analyzing the current amplitudes and dwell-time histograms, thus neglecting the possibility that pore fluctuations (open and closed), usually considered to be stochastic noise, might contain valuable information about the functional aspects of ion channels. Based on the analysis of a deterministic model indicating that the stochastic gating of ion channels could be produced by correlated pore fluctuations, in this work, we analyzed experimental recordings of single channel currents of an inwardly rectifying K+ channel in order to demonstrate the presence of both short and long range correlations in the open and closed pore fluctuations

Dynamic coupling of fast channel gating with slow ATP-turnover underpins protein transport through the Sec translocon.

The Sec translocon is a highly conserved membrane assembly for polypeptide transport across, or into, lipid bilayers. In bacteria, secretion through the core channel complex-SecYEG in the inner membrane-is powered by the cytosolic ATPase SecA. Here, we use single-molecule fluorescence to interrogate the conformational state of SecYEG throughout the ATP hydrolysis cycle of SecA. We show that the SecYEG channel fluctuations between open and closed states are much faster (~20-fold during translocation) than ATP turnover, and that the nucleotide status of SecA modulates the rates of opening and closure. The SecY variant PrlA4, which exhibits faster transport but unaffected ATPase rates, increases the dwell time in the open state, facilitating pre-protein diffusion through the pore and thereby enhancing translocation efficiency. Thus, rapid SecYEG channel dynamics are allosterically coupled to SecA via modulation of the energy landscape, and play an integral part in protein transport. Loose coupling of ATP-turnover by SecA to the dynamic properties of SecYEG is compatible with a Brownian-rachet mechanism of translocation, rather than strict nucleotide-dependent interconversion between different static states of a power stroke.

Intracellular Dynamics of Human Cardiac Ventricular Myocyte: ORd Model

Human heart is elegantly articulated to mechanically contract in response to electrical excitation. Cardiac electrical activity may be described as a multiscale process from sub-cellular to cellular to tissue level. Ion movement at the cellular level through ion channels results in an action potential that propagates as an electrical wave in tissue. A first-principles-based mathematical description of the cellular-level dynamics of cardiac electrophysiological behavior provides a better understanding of the functioning of the heart. The mathematical models describing cellular dynamics often involve a coupled system of ordinary differential equations (ODEs) with variables including transmembrane voltage, ion concentrations and ion channel gating variables, whose evolution describes activation/inactivation of ion channels. In this study we discuss a mathematical model of the human ventricular myocyte (O’Hara–Rudy model), defined as a system of 41 ODEs, with variables involving membrane voltage, 29 gating variables describing activation of Na[Formula: see text], K[Formula: see text], Ca[Formula: see text] channels, 11 variables describing ion concentrations and Ca[Formula: see text] related flux. Runge–Kutta method with variable order and variable time step was adopted to solve the system numerically. We discuss the action potential (AP) profile of a healthy human ventricular myocyte and corresponding dominant ionic currents. We present a phase plot that describes the change in voltage and its rate as the system evolves over time. The phase plot seems to provide more details of the underlying events than the AP curve.

Thermoring basis for the TRPV3 bio-thermometer

The thermosensitive transient receptor potential (TRP) channels are well-known as bio-thermometers with specific temperature thresholds and sensitivity. However, their precise structural origins are still mysterious. Here, graph theory was used to test how the temperature-dependent non-covalent interactions as identified in the 3D structures of thermo-gated TRPV3 could form a systematic fluidic grid-like mesh network with the constrained thermo-rings from the biggest grids to the smallest ones as necessary structural motifs for the variable temperature thresholds and sensitivity. The results showed that the heat-evoked melting of the biggest grids may control the specific temperature thresholds to initiate channel gating while the smaller grids may be required to secure heat efficacy. Together, all the grids along the lipid-dependent minimal gating pathway may be necessary to change with molar heat capacity for the specific temperature sensitivity. Therefore, this graph theory-based grid thermodynamic model may provide an extensive structural basis for the thermo-gated TRP channels.

Permeant cations modulate pore dynamics and gating of TRPV1 ion channels.

The transient receptor vanilloid 1 (TRPV1) is a non-selective ion channel, which is activated by several chemical ligands and heat. We have previously shown that activation of TRPV1 by different ligands results in single-channel openings with different conductance, suggesting that the selectivity filter is highly dynamic. TRPV1 is weakly voltage dependent; here, we sought to explore whether the permeation of different monovalent ions could influence the voltage dependence of this ion channel. By using single-channel recordings, we show that TRPV1 channels undergo rapid transitions to closed states that are directly connected to the open state, which may result from structural fluctuations of their selectivity filter. Moreover, we demonstrate that the rates of these transitions are influenced by the permeant ion, suggesting that ion permeation regulates the voltage dependence of these channels. Our data could be the basis for more detailed MD simulations exploring the permeation mechanism and how the occupancy of different ions alters the three-dimensional structure of the pore of TRPV1 channels.

Speedy stomata of a C4 plant correlate with enhanced K+ channel gating.

Stomata are microscopic pores at the surface of plant leaves that facilitate gaseous diffusion to support photosynthesis. The guard cells around each stoma regulate the pore aperture. Plants that carry out C4 photosynthesis are usually more resilient than C3 plants to stress, and their stomata operate over a lower dynamic range of CO2 within the leaf. What makes guard cells of C4 plants more responsive than those of C3 plants? We used gas exchange and electrophysiology, comparing stomatal kinetics of the C4 plant Gynandropsis gynandra and the phylogenetically related C3 plant Arabidopsis thaliana. We found, with varying CO2 and light, that Gynandropsis showed faster changes in stomata conductance and greater water use efficiency when compared with Arabidopsis. Electrophysiological analysis of the dominant K+ channels showed that the outward-rectifying channels, responsible for K+ loss during stomatal closing, were characterised by a greater maximum conductance and substantial negative shift in the voltage dependence of gating, indicating a reduced inhibition by extracellular K+ and enhanced capacity for K+ flux. These differences correlated with the accelerated stomata kinetics of Gynandropsis, suggesting that subtle changes in the biophysical properties of a key transporter may prove a target for future efforts to engineer C4 stomatal kinetics.

Two-dimensional analytical model for fully depleted SOI MOSFETs with vertical trapezoid doping including effects of the interface trapped charges

The two-dimensional (2D) potential distribution for vertical trapezoidal doping thin-body fully depleted (FD) silicon-on-insulator (SOI) devices is derived by adopting the evanescent mode analysis method, in which the 2D effects in gate oxide region, channel region and buried oxide region are taken into account. Moreover, the effects of interface trapped charge are considered. Using this potential model, the subthreshold performance of the device including subthreshold current, and subthreshold swing under various conditions have been studied. The result shows that the analytical model is good agreement with the simulated results. Therefore, it provides a feasible way of developing new 2D models for vertical trapezoidal doping thin-body FD SOI devices. Besides offering the physical insight into device physics, the analytical model provides the basic designing guidance for vertical trapezoidal doping thin-body FD SOI devices.

Membrane lipid modulations by methyl-β-cyclodextrin uncouple the Drosophila light-activated phospholipase C from TRP and TRPL channel gating

Sterols are hydrophobic molecules, known to cluster signaling membrane-proteins in lipid-rafts, while methyl-β-cyclodextrin (MβCD) has been a major tool for modulating membrane-sterol content to study its effect on membrane proteins, including the Transient Receptor Potential (TRP) channels. The Drosophila light-sensitive TRP channels are activated downstream of a G-protein-coupled phospholipase Cβ (PLC) cascade. In phototransduction, PLC is a critical enzyme that hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) generating diacylglycerol (DAG), inositol-tris-phosphate (IP3) and protons, leading to TRP and TRP-like (TRPL) channel openings. Here we studied the effects of MβCD on Drosophila phototransduction using electrophysiology while fluorescently-monitoring PIP2 hydrolysis, aiming to examine the effects of sterol modulation on PIP2 hydrolysis and the ensuing light-response in the native system. Incubation of photoreceptor cells with MβCD dramatically reduced the amplitude and kinetics of the TRP/TRPL-mediated light-response. MβCD also suppressed PLC-dependent TRP/TRPL constitutive channel activity in the dark induced by mitochondrial uncouplers, but PLC independent activation of the channels by linoleic acid was not affected. Furthermore, MβCD suppressed a constitutively-active TRP mutant-channel, trpP365, suggesting that TRP channel activity is a target of MβCD action. Importantly, whole-cell voltage-clamp measurements from photoreceptor cells and simultaneously monitored PIP2 hydrolysis by translocation of fluorescently-tagged lipid-binding-Tubby-protein domain, from the plasma membrane to the cytosol revealed that MβCD virtually abolished the light-response when having only little effect on the light-activated PIP2 hydrolysis by PLC. Together, MβCD uncoupled TRP/TRPL channel gating from light-activated PLC and PIP2-hydrolysis suggest the involvement of distinct nanoscopic lipid domains such as lipid-rafts and PIP2-clusters in TRP/TRPL channel gating.

Genotype-phenotype correlation in Taiwanese children with diazoxide-unresponsive congenital hyperinsulinism.

Congenital hyperinsulinism (CHI) is a group of clinically and genetically heterogeneous disorders characterized by dysregulated insulin secretion. The aim of the study was to elucidate genetic etiologies of Taiwanese children with the most severe diazoxide-unresponsive CHI and analyze their genotype-phenotype correlations. We combined Sanger with whole exome sequencing (WES) to analyze CHI-related genes. The allele frequency of the most common variant was estimated by single-nucleotide polymorphism haplotype analysis. The functional effects of the ATP-sensitive potassium (KATP) channel variants were assessed using patch clamp recording and Western blot. Nine of 13 (69%) patients with ten different pathogenic variants (7 in ABCC8, 2 in KCNJ11 and 1 in GCK) were identified by the combined sequencing. The variant ABCC8 p.T1042QfsX75 identified in three probands was located in a specific haplotype. Functional study revealed the human SUR1 (hSUR1)-L366F KATP channels failed to respond to intracellular MgADP and diazoxide while hSUR1-R797Q and hSUR1-R1393C KATP channels were defective in trafficking. One patient had a de novo dominant mutation in the GCK gene (p.I211F), and WES revealed mosaicism of this variant from another patient. Pathogenic variants in KATP channels are the most common underlying cause of diazoxide-unresponsive CHI in the Taiwanese cohort. The p.T1042QfsX75 variant in the ABCC8 gene is highly suggestive of a founder effect. The I211F mutation in the GCK gene and three rare SUR1 variants associated with defective gating (p.L366F) or traffic (p.R797Q and p.R1393C) KATP channels are also associated with the diazoxide-unresponsive phenotype.

Synthesis and Characterization of Stimuli-Responsive Polymer Brushes in Nanofluidic Channels.

Nanochannels with controllable gating behavior are attractive features in a wide range of nanofluidic applications including viral detection, particle sorting, and flow regulation. Here, we use selective sidewall functionalization of nanochannels with a polyelectrolyte brush to investigate the channel gating response to variations in solution pH and ionic strength. The conformational and structural changes of the interfacial brush layer within the channels are interrogated by specular and off-specular neutron reflectometry. Simultaneous fits of the specular and off-specular signals, using a dynamical theory model and a fitting optimization protocol, enable detailed characterization of the brush conformations and corresponding channel geometry under different solution conditions. Our results indicate a collapsed brush state under basic pH, equivalent to an open gate, and an expanded brush state representing a partially closed gate upon decreasing the pH and salt concentration. These findings open new possibilities in noninvasive in situ characterization of tunable nanofluidics and lab-on-chip devices with advanced designs and improved functionality.

Calcium-Sensitive Subthreshold Oscillations and Electrical Coupling in Principal Cells of Mouse Dorsal Cochlear Nucleus.

In higher sensory brain regions, slow oscillations (0.5-5 Hz) associated with quiet wakefulness and attention modulate multisensory integration, predictive coding, and perception. Although often assumed to originate via thalamocortical mechanisms, the extent to which subcortical sensory pathways are independently capable of slow oscillatory activity is unclear. We find that in the first station for auditory processing, the cochlear nucleus, fusiform cells from juvenile mice (of either sex) generate robust 1-2 Hz oscillations in membrane potential and exhibit electrical resonance. Such oscillations were absent prior to the onset of hearing, intrinsically generated by hyperpolarization-activated cyclic nucleotide-gated (HCN) and persistent Na+ conductances (NaP) interacting with passive membrane properties, and reflected the intrinsic resonance properties of fusiform cells. Cx36-containing gap junctions facilitated oscillation strength and promoted pairwise synchrony of oscillations between neighboring neurons. The strength of oscillations were strikingly sensitive to external Ca2+, disappearing at concentrations >1.7 mM, due in part to the shunting effect of small-conductance calcium-activated potassium (SK) channels. This effect explains their apparent absence in previous in vitro studies of cochlear nucleus which routinely employed high-Ca2+ extracellular solution. In contrast, oscillations were amplified in reduced Ca2+ solutions, due to relief of suppression by Ca2+ of Na+ channel gating. Our results thus reveal mechanisms for synchronous oscillatory activity in auditory brainstem, suggesting that slow oscillations, and by extension their perceptual effects, may originate at the earliest stages of sensory processing.