The Roles Potassium Currents Play in Regulating the Electrical Activity of Ventral Cochlear Nucleus Neurons

2003 ◽  
Vol 89 (6) ◽  
pp. 3097-3113 ◽  
Author(s):  
Jason S. Rothman ◽  
Paul B. Manis
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Threshold Current ◽  
Repetitive Firing ◽  
Resting Membrane Potential ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Ventral Cochlear Nucleus ◽  
Discharge Patterns

Using kinetic data from three different K+ currents in acutely isolated neurons, a single electrical compartment representing the soma of a ventral cochlear nucleus (VCN) neuron was created. The K+ currents include a fast transient current ( IA), a slow-inactivating low-threshold current ( ILT), and a noninactivating high-threshold current ( IHT). The model also includes a fast-inactivating Na+ current, a hyperpolarization-activated cation current ( Ih), and 1–50 auditory nerve synapses. With this model, the role IA, ILT, and IHT play in shaping the discharge patterns of VCN cells is explored. Simulation results indicate that IHT mainly functions to repolarize the membrane during an action potential, and IA functions to modulate the rate of repetitive firing. ILT is found to be responsible for the phasic discharge pattern observed in Type II cells (bushy cells). However, by adjusting the strength of ILT, both phasic and regular discharge patterns are observed, demonstrating that a critical level of ILT is necessary to produce the Type II response. Simulated Type II cells have a significantly faster membrane time constant in comparison to Type I cells (stellate cells) and are therefore better suited to preserve temporal information in their auditory nerve inputs by acting as precise coincidence detectors and having a short refractory period. Finally, we demonstrate that modulation of Ih, which changes the resting membrane potential, is a more effective means of modulating the activation level of ILT than simply modulating ILT itself. This result may explain why ILT and Ih are often coexpressed throughout the nervous system.

Excitatory/inhibitory response types in the cochlear nucleus: relationships to discharge patterns and responses to electrical stimulation of the auditory nerve

1985 ◽  
Vol 54 (4) ◽  
pp. 917-939 ◽  
Author(s):  
W. P. Shofner ◽  
E. D. Young
Keyword(s):  
Receptive Field ◽  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Type I ◽  
Type Ii ◽  
Type Iii ◽  
Rate Level ◽  
Cochlear Nucleus Units ◽  
Excitatory Responses ◽  
Discharge Patterns

We have studied the response properties of single units in the cochlear nucleus of unanesthetized decerebrate cats. The purpose of the study was to compare the properties of cochlear nucleus units as described in two commonly used classification schemes. Units were first classified according to their receptive-field properties based on the relative prominence of excitatory and inhibitory responses to tones and noise. Units were then classified on the basis of their discharge patterns to short tone bursts at their best frequencies (BFs). Our results show that systematic relationships exist between the receptive-field properties and discharge patterns of cochlear nucleus units. Type I units give only excitatory responses to tones and noise. They are characterized by primary-like and chopper discharge patterns. Some units in the anteroventral cochlear nucleus have prepotentials in their spike waveforms. Prepotential units most often show primary-like discharge patterns, but prepotential units characterized by nonprimary-like discharge patterns are also found. Most prepotential units lack detectable inhibitory sidebands (type I), but two of the nonprimary-like prepotential units encountered in this study had inhibitory sidebands (type III). Type III units also give excitatory responses to BF tones, but they have inhibitory sidebands. Most type III units give chopper discharge patterns, and these units can be recorded throughout the cochlear nucleus. Some type III units in the dorsal cochlear nucleus give complex discharge patterns that can be described as a composite of the pauser pattern and other patterns. The complexity of these responses seems to increase as the amount of inhibition at BF increases. Type I/III units give excitatory responses to tones and noise, but have little or no spontaneous activity so they cannot be tested directly for inhibitory responses. Type I/III units typically show chopper discharge patterns. One group of type I/III units have rate-level functions with sloping saturation, suggesting that these may receive a predominance of input from low spontaneous rate auditory nerve fibers. Type II units are nonspontaneous and give excitatory responses to tones, but give weak or no responses to noise. While type II units are homogeneous as a group in terms of their response maps. BF rate-level functions, and responses to noise, they show a variety of discharge patterns in response to short tone bursts at BF.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals CD95 death-inducing signaling complex formation and internalization occur in lipid rafts of type I and type II cells

2004 ◽  
Vol 34 (7) ◽  
pp. 1930-1940 ◽  
Author(s):  
Adriana Eramo ◽  
Massimo Sargiacomo ◽  
Lucia Ricci-Vitiani ◽  
Matilde Todaro ◽  
Giorgio Stassi ◽  
...  
Keyword(s):  
Complex Formation ◽  
Lipid Rafts ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Signaling Complex

Electrophysiology of globus pallidus neurons in vitro

1994 ◽  
Vol 72 (3) ◽  
pp. 1127-1139 ◽  
Author(s):  
A. Nambu ◽  
R. Llinas
Keyword(s):  
Globus Pallidus ◽  
Input Resistance ◽  
Repetitive Firing ◽  
Type I ◽  
Type Ii ◽  
Low Threshold ◽  
Membrane Oscillations ◽  
Neuronal Type ◽  
A Current ◽  
Membrane Level

1. We investigated the electrical properties of globus pallidus neurons intracellularly using brain slices from adult guinea pigs. Three types of neurons were identified according to their intrinsic electrophysiological properties. 2. Type I neurons (59%) were silent at the resting membrane level (-65 +/- 10 mV, mean +/- SD) and generated a burst of spikes, with strong accommodation, to depolarizing current injection. Calcium-dependent low-frequency (1-8 Hz) membrane oscillations were often elicited by membrane depolarization (-53 +/- 8 mV). A low-threshold calcium conductance and an A-current were also identified. The mean input resistance of this neuronal type was 70 +/- 22 M omega. 3. Type II neurons (37%) fired spontaneously at the resting membrane level (-59 +/- 9 mV). Their repetitive firing (< or = 200 Hz) was very sensitive to the amplitude of injected current and showed weak accommodation. Sodium-dependent high-frequency (20-100 Hz) subthreshold membrane oscillations were often elicited by membrane depolarization. This neuronal type demonstrated a low-threshold calcium spike and had the highest input resistance (134 +/- 62 M omega) of the three neuron types. 4. Type III neurons (4%) did not fire spontaneously at the resting membrane level (-73 +/- 5 mV). Their action potentials were characterized by a long duration (2.3 +/- 0.6 ms). Repetitive firing elicited by depolarizing current injection showed weak or no accommodation. This neuronal type had an A-current and showed the lowest input resistance (52 +/- 35 M omega) of the three neuron types. 5. Stimulation of the caudoputamen evoked inhibitory postsynaptic potentials (IPSPs) in Type I and II neurons. In Type II neurons the IPSPs were usually followed by rebound firing. Excitatory postsynaptic potentials and antidromic responses were also elicited in some Type I and II neurons. The estimated conduction velocity of the striopallidal projection was < 1 m/s (Type I neurons, 0.49 +/- 0.37 m/s; Type II neurons, 0.33 +/- 0.13 m/s).

Disparate cytokine regulation of ICAM-1 in rat alveolar epithelial cells and pulmonary endothelial cells in vitro

1995 ◽  
Vol 269 (1) ◽  
pp. L127-L135 ◽  
Author(s):  
W. W. Barton ◽  
S. Wilcoxen ◽  
P. J. Christensen ◽  
R. Paine
Keyword(s):  
Endothelial Cells ◽  
Epithelial Cells ◽  
Inflammatory Cytokines ◽  
Alveolar Epithelial Cells ◽  
Normal Lung ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Epithelial

Intercellular adhesion molecule-1 (ICAM-1) is expressed at high levels on type I alveolar epithelial cells in the normal lung and is induced in vitro as type II cells spread in primary culture. In contrast, in most nonhematopoetic cells ICAM-1 expression is induced in response to inflammatory cytokines. We have formed the hypothesis that the signals that control ICAM-1 expression in alveolar epithelial cells are fundamentally different from those controlling expression in most other cells. To test this hypothesis, we have investigated the influence of inflammatory cytokines on ICAM-1 expression in isolated type II cells that have spread in culture and compared this response to that of rat pulmonary artery endothelial cells (RPAEC). ICAM-1 protein, determined both by a cell-based enzyme-linked immunosorbent assay and by Western blot analysis, and mRNA were minimally expressed in unstimulated RPAEC but were significantly induced in a time- and dose-dependent manner by treatment with tumor necrosis factor-alpha, interleukin-1 beta, or interferon-gamma. In contrast, these cytokines did not influence the constitutive high level ICAM-1 protein expression in alveolar epithelial cells and only minimally affected steady-state mRNA levels. ICAM-1 mRNA half-life, measured in the presence of actinomycin D, was relatively long at 7 h in alveolar epithelial cells and 4 h in RPAEC. The striking lack of response of ICAM-1 expression by alveolar epithelial cells to inflammatory cytokines is in contrast to virtually all other epithelial cells studied to date and supports the hypothesis that ICAM-1 expression by these cells is a function of cellular differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Encoding timing and intensity in the ventral cochlear nucleus of the cat

1986 ◽  
Vol 56 (2) ◽  
pp. 261-286 ◽  
Author(s):  
W. S. Rhode ◽  
P. H. Smith
Keyword(s):  
Firing Rate ◽  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Cell Types ◽  
Nerve Fibers ◽  
Frequency Selectivity ◽  
Firing Rates ◽  
Ventral Cochlear Nucleus ◽  
Auditory Nerve Fibers ◽  
Different Cell Types

Physiological response properties of neurons in the ventral cochlear nucleus have a variety of features that are substantially different from the stereotypical auditory nerve responses that serve as the principal source of activation for these neurons. These emergent features are the result of the varying distribution of auditory nerve inputs on the soma and dendrites of the various cell types within the nucleus; the intrinsic membrane characteristics of the various cell types causing different responses to the same input in different cell types; and secondary excitatory and inhibitory inputs to different cell types. Well-isolated units were recorded with high-impedance glass microelectrodes, both intracellularly and extracellularly. Units were characterized by their temporal response to short tones, rate vs. intensity relation, and response areas. The principal response patterns were onset, chopper, and primary-like. Onset units are characterized by a well-timed first spike in response to tones at the characteristic frequency. For frequencies less than 1 kHz, onset units can entrain to the stimulus frequency with greater precision than their auditory nerve inputs. This implies that onset units receive converging inputs from a number of auditory nerve fibers. Onset units are divided into three subcategories, OC, OL, and OI. OC units have extraordinarily wide dynamic ranges and low-frequency selectivity. Some are capable of sustaining firing rates of 800 spikes/s at high intensities. They have the smallest standard deviation and coefficient of variation of the first spike latency of any cells in the cochlear nuclei. OC units are candidates for encoding intensity. OI and OL units differ from OC units in that they have dynamic ranges and frequency selectivity ranges much like those of auditory nerve fibers. They differ from one another in their steady-state firing rates; OI units fire mainly at the onset of a tone. OI units also differ from OL units in that they prefer frequency sweeps in the low to high direction. Primary-like-with-notch (PLN) units also respond to tones with a well-timed first spike. They differ from onset cells in that the onset peak is not always as precise as the spontaneous rate is higher. A comparison of spontaneous firing rate and saturation firing rate of PLN units with auditory nerve fibers suggest that PLN units receive one to four auditory nerve fiber inputs. Chopper units fire in a sustained regular manner when they are excited by sound.(ABSTRACT TRUNCATED AT 400 WORDS)

Modelling the sensitivity of cells in the anteroventral cochlear nucleus to spatiotemporal discharge patterns

1992 ◽  
Vol 336 (1278) ◽  
pp. 403-406 ◽  
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Cross Correlation ◽  
Low Frequency ◽  
Phase Spectrum ◽  
Coincidence Detection ◽  
Potential Mechanism ◽  
Complex Sounds ◽  
Anteroventral Cochlear Nucleus ◽  
Discharge Patterns

This study investigates a potential mechanism for the processing of acoustic information that is encoded in the spatiotemporal discharge patterns of auditory nerve (AN) fibres. Recent physiological evidence has demonstrated that some low-frequency cells in the anteroventral cochlear nucleus (AVCN) are sensitive to manipulations of the phase spectrum of complex sounds (Carney 1990 b ). These manipulations result in systematic changes in the spatiotemporal discharge patterns across groups of low-frequency an fibres having different characteristic frequencies (CFS). One interpretation of these results is that these neurons in the AVCN receive convergent inputs from AN fibres with different CFS, and that the cells perform a coincidence detection or cross-correlation upon their inputs. This report presents a model that was developed to test this interpretation.

Sulfation of extracellular matrices modifies responses of alveolar type II cells to fibroblast growth factors

1996 ◽  
Vol 271 (5) ◽  
pp. L688-L697 ◽  
Author(s):  
P. L. Sannes ◽  
J. Khosla ◽  
P. W. Cheng
Keyword(s):  
Growth Factors ◽  
Biological Significance ◽  
Alveolar Type ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Fibroblast Growth ◽  
Alveolar Type Ii Cells ◽  
Proliferation And Differentiation ◽  
Type Ii Cell

The pulmonary alveolar basement membrane (BM) associated with alveolar type II cells has been shown to be significantly less sulfated than that of type I cells. To examine the biological significance of this observation, we measured the incorporation of 5-bromodeoxyuridine (BrdU) as an indicator of DNA synthesis in isolated rat type II cells cultured for 72-120 h on substrata that were naturally sulfated, not sulfated, or chemically desulfated in serum-free, hormonally defined media, with and without selected growth factors. The percentage of cells incorporating BrdU was significantly elevated by desulfated chondroitin sulfate in the presence of fibroblast growth factor-2 (FGF-2 or basic FGF) and depressed by heparin in the presence of either FGF-1 or acidic FGF or FGF-2. This depressive effect was lost by removing sulfate from the heparin. Some responses were dependent on the period of time in culture and concentration and molecular weight of the substrata. These observations support the notion that sulfation per se of certain components of BM is a key determinant of type II cell responses to select growth factors that may define patterns of proliferation and differentiation.

Differential Expression of Three Distinct Potassium Currents in the Ventral Cochlear Nucleus

2003 ◽  
Vol 89 (6) ◽  
pp. 3070-3082 ◽  
Author(s):  
Jason S. Rothman ◽  
Paul B. Manis
Keyword(s):  
Differential Expression ◽  
Cochlear Nucleus ◽  
Nerve Fibers ◽  
Delayed Rectifier ◽  
High Threshold ◽  
Type I ◽  
Acoustic Environment ◽  
Ventral Cochlear Nucleus ◽  
Wide Range ◽  
Slope Factor

In the ventral cochlear nucleus (VCN), neurons transform information from auditory nerve fibers into a set of parallel ascending pathways, each emphasizing different aspects of the acoustic environment. Previous studies have shown that VCN neurons differ in their intrinsic electrical properties, including the K+ currents they express. In this study, we examine these K+ currents in more detail using whole cell voltage-clamp techniques on isolated VCN cells from adult guinea pigs at 22°C. Our results show a differential expression of three distinct K+ currents. Whereas some VCN cells express only a high-threshold delayed-rectifier-like current ( IHT), others express IHT in combination with a fast inactivating current ( IA) and/or a slow-inactivating low-threshold current ( ILT). IHT, ILT, and IA, were partially blocked by 1 mM 4-aminopyridine. In contrast, only ILT was blocked by 10–100 nM dendrotoxin-I. A surprising finding was the wide range of levels of ILT, suggesting ILT is expressed as a continuum across cell types rather than modally in a particular cell type. IA, on the other hand, appears to be expressed only in cells that show little or no ILT, the Type I cells. Boltzmann analysis shows IHT activates with 164 ± 12 (SE) nS peak conductance, -14.3 ± 0.7 mV half-activation, and 7.0 ± 0.5 mV slope factor. Similar analysis shows ILT activates with 171 ± 22 nS peak conductance, -47.4 ± 1.0 mV half-activation, and 5.8 ± 0.3 mV slope factor.

Sign in / Sign up

Export Citation Format

Share Document