Molecular identity, ontogeny, and cAMP modulation of the hyperpolarization-activated current in vestibular ganglion neurons

2012 ◽  
Vol 108 (8) ◽  
pp. 2264-2275 ◽  
Author(s):  
Angélica Almanza ◽  
Enoch Luis ◽  
Francisco Mercado ◽  
Rosario Vega ◽  
Enrique Soto
Keyword(s):  
Current Density ◽  
Small Cells ◽  
Resting Potential ◽  
Afferent Neuron ◽  
Intracellular Camp ◽  
Rt Pcr ◽  
Patch Clamp Technique ◽  
Vestibular Ganglion ◽  
Hyperpolarization Activated Current ◽  
Ganglion Neurons

Properties, developmental regulation, and cAMP modulation of the hyperpolarization-activated current ( Ih) were investigated by the whole cell patch-clamp technique in vestibular ganglion neurons of the rat at two postnatal stages (P7–10 and P25–28). In addition, by RT-PCR and immunohistochemistry the identity and distribution of hyperpolarization-activated and cyclic nucleotide-gated channel (HCN) isoforms that generate Ih were investigated. Ih current density was larger in P25–28 than P7–10 rats, increasing 410% for small cells (<30 pF) and 200% for larger cells (>30 pF). The half-maximum activation voltage ( V1/2) of Ih was −102 mV in P7–10 rats and in P25–28 rats shifted 7 mV toward positive voltages. At both ages, intracellular cAMP increased Ih current density, decreased its activation time constant (τ), and resulted in a rightward shift of V1/2 by 9 mV. Perfusion of 8-BrcAMP increased Ih amplitude and speed up its activation kinetics. Ih was blocked by Cs+, zatebradine, and ZD7288. As expected, these drugs also reduced the voltage sag caused with hyperpolarizing pulses and prevented the postpulse action potential generation without changes in the resting potential. RT-PCR analysis showed that HCN1 and HCN2 subunits were predominantly amplified in vestibular ganglia and end organs and HCN3 and HCN4 to a lesser extent. Immunohistochemistry showed that the four HCN subunits were differentially expressed (HCN1 > HCN2 > HCN3 ≥ HCN4) in ganglion slices and in cultured neurons at both P7–10 and P25–28 stages. Developmental changes shifted V1/2 of Ih closer to the resting membrane potential, increasing its functional role. Modulation of Ih by cAMP-mediated signaling pathway constitutes a potentially relevant control mechanism for the modulation of afferent neuron discharge.

scholarly journals A biophysical model examining the role of low-voltage-activated potassium currents in shaping the responses of vestibular ganglion neurons

2016 ◽  
Vol 116 (2) ◽  
pp. 503-521 ◽  
Author(s):  
Ariel E. Hight ◽  
Radha Kalluri
Keyword(s):  
Low Voltage ◽  
Potassium Currents ◽  
Synaptic Conductance ◽  
Biophysical Model ◽  
Resting Potential ◽  
Interspike Intervals ◽  
Firing Patterns ◽  
Vestibular Ganglion ◽  
Ganglion Neurons ◽  
The Impact

The vestibular nerve is characterized by two broad groups of neurons that differ in the timing of their interspike intervals; some fire at highly regular intervals, whereas others fire at highly irregular intervals. Heterogeneity in ion channel properties has been proposed as shaping these firing patterns (Highstein SM, Politoff AL. Brain Res 150: 182–187, 1978; Smith CE, Goldberg JM. Biol Cybern 54: 41–51, 1986). Kalluri et al. ( J Neurophysiol 104: 2034–2051, 2010) proposed that regularity is controlled by the density of low-voltage-activated potassium currents ( IKL). To examine the impact of IKL on spike timing regularity, we implemented a single-compartment model with three conductances known to be present in the vestibular ganglion: transient sodium ( gNa), low-voltage-activated potassium ( gKL), and high-voltage-activated potassium ( gKH). Consistent with in vitro observations, removing gKL depolarized resting potential, increased input resistance and membrane time constant, and converted current step-evoked firing patterns from transient (1 spike at current onset) to sustained (many spikes). Modeled neurons were driven with a time-varying synaptic conductance that captured the random arrival times and amplitudes of glutamate-driven synaptic events. In the presence of gKL, spiking occurred only in response to large events with fast onsets. Models without gKL exhibited greater integration by responding to the superposition of rapidly arriving events. Three synaptic conductance were modeled, each with different kinetics to represent a variety of different synaptic processes. In response to all three types of synaptic conductance, models containing gKL produced spike trains with irregular interspike intervals. Only models lacking gKL when driven by rapidly arriving small excitatory postsynaptic currents were capable of generating regular spiking.

scholarly journals Similarities in the Biophysical Properties of Spiral-Ganglion and Vestibular-Ganglion Neurons in Neonatal Rats

2021 ◽  
Vol 15 ◽  
Author(s):  
Radha Kalluri
Keyword(s):  
Sensory Modality ◽  
Spiral Ganglion ◽  
Input Resistance ◽  
Resting Potential ◽  
Biophysical Properties ◽  
Firing Patterns ◽  
Vestibular Ganglion ◽  
Large Current ◽  
Ganglion Neurons ◽  
Diverse Groups

The membranes of auditory and vestibular afferent neurons each contain diverse groups of ion channels that lead to heterogeneity in their intrinsic biophysical properties. Pioneering work in both auditory- and vestibular-ganglion physiology have individually examined this remarkable diversity, but there are few direct comparisons between the two ganglia. Here the firing patterns recorded by whole-cell patch-clamping in neonatal vestibular- and spiral ganglion neurons are compared. Indicative of an overall heterogeneity in ion channel composition, both ganglia exhibit qualitatively similar firing patterns ranging from sustained-spiking to transient-spiking in response to current injection. The range of resting potentials, voltage thresholds, current thresholds, input-resistances, and first-spike latencies are similarly broad in both ganglion groups. The covariance between several biophysical properties (e.g., resting potential to voltage threshold and their dependence on postnatal age) was similar between the two ganglia. Cell sizes were on average larger and more variable in VGN than in SGN. One sub-group of VGN stood out as having extra-large somata with transient-firing patterns, very low-input resistance, fast first-spike latencies, and required large current amplitudes to induce spiking. Despite these differences, the input resistance per unit area of the large-bodied transient neurons was like that of smaller-bodied transient-firing neurons in both VGN and SGN, thus appearing to be size-scaled versions of other transient-firing neurons. Our analysis reveals that although auditory and vestibular afferents serve very different functions in distinct sensory modalities, their biophysical properties are more closely related by firing pattern and cell size than by sensory modality.

Properties of the hyperpolarization-activated current in rat hippocampal CA1 pyramidal cells

1993 ◽  
Vol 69 (6) ◽  
pp. 2129-2136 ◽  
Author(s):  
G. Maccaferri ◽  
M. Mangoni ◽  
A. Lazzari ◽  
D. DiFrancesco
Keyword(s):  
Membrane Conductance ◽  
Pyramidal Cells ◽  
Resting Potential ◽  
Constant Current ◽  
Patch Clamp Technique ◽  
Current Activation ◽  
Hyperpolarization Activated Current ◽  
K Concentration ◽  
Current Steps

1. Voltage and current clamp recordings were performed on CA1 rat hippocampal pyramidal cells using the patch clamp technique on "in vitro" slice preparations. 2. Hyperpolarizations from a holding potential of -35 mV elicited activation of the hyperpolarization-activated current (Ih) starting at voltages near -50 mV. 3. Ih recorded in voltage clamp conditions was blocked by external caesium (5 mM). 4. Raising the external K concentration from 4.35 to 24.35 mM sensibly increased the slope of the current-voltage (I/V) curve. Decreasing the external Na concentration from 133.5 to 33.5 mM depressed Ih without grossly altering the I/V slope. 5. The Ih fully activated I/V relation measured in the range -140 to -45 mV was linear with an extrapolated reversal at -17.0 +/- -1.6 (SE) mV. The current activation curve comprised the range between about -50 and -140 mV with a half-maximal activation at about -98 mV. 6. Perfusion of unclamped neurons with Cs (2 mM) hyperpolarized their resting potential by 3.8 +/- 0.2 mV and decreased the membrane conductance, as expected if Ih were activated at rest. Firing caused by depolarizing current steps was prevented by Cs-induced hyperpolarization, and could be restored by returning the membrane voltage to resting level by constant current injection. 7. The Cd-insensitive (medium-duration) afterhyperpolarization (AHP) elicited by a train of action potentials at -60 mV had an amplitude of 3.9 +/- 0.3 mV and was nearly fully abolished by 2 mM Cs (82.7 +/- 7.4%). Cs removed the depolarizing part of the afterhyperpolarization as expected if Ih activation was responsible for this phase.(ABSTRACT TRUNCATED AT 250 WORDS)

cAMP-dependent phosphorylation modulates voltage gating in an endothelial Cl- channel

1993 ◽  
Vol 264 (2) ◽  
pp. C370-C375 ◽  
Author(s):  
L. Vaca ◽  
D. L. Kunze
Keyword(s):  
Voltage Dependence ◽  
Surface Membrane ◽  
Resting Potential ◽  
Disulfonic Acid ◽  
Intracellular Camp ◽  
Adrenergic Stimulation ◽  
Patch Clamp Technique ◽  
Cyclic Monophosphate ◽  
Cl Channel ◽  
Inside Out

Using the patch clamp technique in the cell-attached, inside-out, and outside-out configurations, we have identified a voltage-gated outwardly rectifying, large conductance (400 pS) Cl- channel in patches from the surface membrane of a cultured monolayer of bovine aortic endothelial cells. The channel is activated in cell-attached patches with 1 microM isoproterenol or 1 mM dibutyryladenosine 3',5'-cyclic monophosphate. In excised inside-out patches the voltage dependence of this channel could be fitted by a Boltzmann distribution with a half-activation voltage (V1/2) at 0 mV. Adenosine 3',5'-cyclic monophosphate (cAMP)-dependent phosphorylation induces a shift of -50 mV in V1/2. Alkaline phosphatases restores the voltage dependence of the channel to control values. The channel is reversibly blocked by 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid. The half-inhibitory concentration was approximately 70 microM. Our results suggest that beta-adrenergic stimulation (which increases intracellular cAMP levels in this endothelium) may increase Cl- permeability at the cell resting potential by shifting the voltage dependence of this channel.

scholarly journals P2X2 receptors differentiate placodal vs. neural crest C-fiber phenotypes innervating guinea pig lungs and esophagus

2008 ◽  
Vol 295 (5) ◽  
pp. L858-L865 ◽  
Author(s):  
Kevin Kwong ◽  
Marian Kollarik ◽  
Christina Nassenstein ◽  
Fei Ru ◽  
Bradley J. Undem
Keyword(s):  
Guinea Pig ◽  
Neural Crest ◽  
Single Cell ◽  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
Receptor Activation ◽  
Rt Pcr ◽  
C Fibers ◽  
Embryonic Origin ◽  
Ganglion Neurons

The lungs and esophagus are innervated by sensory neurons with somata in the nodose, jugular, and dorsal root ganglion. These sensory ganglia are derived from embryonic placode (nodose) and neural crest tissues (jugular and dorsal root ganglia; DRG). We addressed the hypothesis that the neuron's embryonic origin (e.g., placode vs. neural crest) plays a greater role in determining particular aspects of its phenotype than the environment in which it innervates (e.g., lungs vs. esophagus). This hypothesis was tested using a combination of extracellular and patch-clamp electrophysiology and single-cell RT-PCR from guinea pig neurons. Nodose, but not jugular C-fibers innervating the lungs and esophagus, responded to α,β-methylene ATP with action potential discharge that was sensitive to the P2X3 (P2X2/3) selective receptor antagonist A-317491. The somata of lung- and esophagus-specific sensory fibers were identified using retrograde tracing with a fluorescent dye. Esophageal- and lung-traced neurons from placodal tissue (nodose neurons) responded similarly to α,β-methylene ATP (30 μM) with a large sustained inward current, whereas in neurons derived from neural crest tissue (jugular and DRG neurons), the same dose of α,β-methylene ATP resulted in only a transient rapidly inactivating current or no detectable current. It has been shown previously that only activation of P2X2/3 heteromeric receptors produce sustained currents, whereas homomeric P2X3 receptor activation produces a rapidly inactivating current. Consistent with this, single-cell RT-PCR analysis revealed that the nodose ganglion neurons innervating the lungs and esophagus expressed mRNA for P2X2 and P2X3 subunits, whereas the vast majority of jugular and dorsal root ganglia innervating these tissues expressed only P2X3 mRNA with little to no P2X2 mRNA expression. We conclude that the responsiveness of C-fibers innervating the lungs and esophagus to ATP and other purinergic agonists is determined more by their embryonic origin than by the environment of the tissue they ultimately innervate.

Plasticity of KIR channels in human smooth muscle cells from internal thoracic artery

2003 ◽  
Vol 284 (6) ◽  
pp. H2325-H2334 ◽  
Author(s):  
Tom Karkanis ◽  
Shaohua Li ◽  
J. Geoffrey Pickering ◽  
Stephen M. Sims
Keyword(s):  
Smooth Muscle ◽  
Current Density ◽  
Internal Thoracic Artery ◽  
Smooth Muscles ◽  
Vascular Smooth Muscles ◽  
Rt Pcr ◽  
Regulation Of Proliferation ◽  
Negative Membrane Potential ◽  
Inwardly Rectifying ◽  
Contractile Cells

Inwardly rectifying K+ (KIR) currents are present in some, but not all, vascular smooth muscles. We used patch-clamp methods to examine plasticity of this current by comparing contractile and proliferative phenotypes of a clonal human vascular smooth muscle cell line. Hyperpolarization of cells under voltage clamp elicited a large inward current that was selective for K+ and blocked by Ba2+. Current density was greater in proliferative compared with contractile cells (−4.5 ± 0.9 and −1.4 ± 0.3 pA/pF, respectively; P < 0.001). RT-PCR of mRNA from proliferative cells identified transcripts for Kir2.1 and Kir2.2 but not Kir2.3 potassium channels. Western blot analysis demonstrated greater expression of Kir2.1 protein in proliferative cells, consistent with the higher current density. Proliferative cells displayed a more negative membrane potential than contractile cells (−71 ± 2 and −35 ± 4 mV, respectively; P < 0.001). Ba2+ depolarized all cells, whereas small increases in extracellular K+ concentration elicited hyperpolarization only in contractile cells. Ba2+ inhibited [3H]thymidine incorporation, indicating a possible role for KIR channels in the regulation of proliferation. The phenotype-dependent plasticity of KIR channels may have relevance to vascular remodeling.

scholarly journals Identification and modelling of fast and slow I h current components in vestibular ganglion neurons

2015 ◽  
Vol 42 (10) ◽  
pp. 2867-2877 ◽  
Author(s):  
Christophe B. Michel ◽  
Christine Azevedo Coste ◽  
Gilles Desmadryl ◽  
Jean‐Luc Puel ◽  
Jerome Bourien ◽  
...  
Keyword(s):  
Vestibular Ganglion ◽  
Ganglion Neurons

Some properties of acetylcholine receptors in human cultured myotubes

1985 ◽  
Vol 224 (1235) ◽  
pp. 183-196 ◽  
Keyword(s):  
Acetylcholine Receptors ◽  
Single Channel ◽  
Fold Increase ◽  
Resting Potential ◽  
Patch Clamp Technique ◽  
Membrane Hyperpolarization ◽  
Human Myotubes ◽  
Cultured Myotubes ◽  
Channel Open Time ◽  
Ach Receptors

The distribution and single channel properties of acetylcholine (ACh) receptors in human myotubes grown in tissue culture have been examined. Radioautography of myotubes labelled with [ 125 I]α-bungarotoxin showed that ACh receptors are distributed uniformly over the myotube surface at a density of 3.9 ± 0.5 receptors per square micrometre. Ac­cumulations of ACh receptors (hot spots) were found rarely. The conductance and kinetics of ACh-activated channels were investi­gated with the patch-clamp technique. Cell-attached membrane patches were used in all experiments. A single channel conductance in the range 40–45 pS was calculated. No sublevels of conductance (substates) of the activated channel were observed. The distribution of channel open-times varied with ACh concentration. With 100 nM ACh, the distribution was best fitted by the sum of two exponentials, whereas with 1 μM ACh a single exponential could be fitted. The mean channel open-time at the myotube resting potential (ca. — 70 mV, 22°C) was 8.2 ms. The distribution of channel closed-times was complex at all concentrations of ACh studied (100 nM to 10 μm). With desensitizing doses of ACh (10 μM), channel openings occurred in obvious bursts; each burst usually appeared as part of a ‘cluster’ of bursts. Both burst duration and mean interval between bursts increased with membrane hyperpolarization. Individual channel open-times and burst durations showed similar voltage dependence (e-fold increase per 80 mV hyperpolarization), whereas both the channel closed-times within a burst and the number of openings per burst were independent of membrane potential.

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