scholarly journals Do connexin channels have a residual conductance state?

1996 ◽  
Vol 70 (2) ◽  
pp. 1082-1084 ◽  
Author(s):  
R.D. Veenstra
Keyword(s):  
Conductance State ◽  
Residual Conductance

scholarly journals An Anionic Ryanoid, 10-O-succinoylryanodol, Provides Insights into the Mechanisms Governing the Interaction of Ryanoids and the Subsequent Altered Function of Ryanodine-receptor Channels

2003 ◽  
Vol 121 (6) ◽  
pp. 551-561 ◽  
Author(s):  
Bhavna Tanna ◽  
William Welch ◽  
Luc Ruest ◽  
John L. Sutko ◽  
Alan J. Williams
Keyword(s):  
Ryanodine Receptor ◽  
Transmembrane Potential ◽  
Voltage Dependence ◽  
Major Influence ◽  
Ionic Interactions ◽  
Receptor Affinity ◽  
Flexible Molecule ◽  
Ion Translocation ◽  
Conductance States ◽  
Conductance State

We have investigated the interactions of a novel anionic ryanoid, 10-O-succinoylryanodol, with individual mammalian cardiac muscle ryanodine receptor channels under voltage clamp conditions. As is the case for all ryanoids so far examined, the interaction of 10-O-succinoylryanodol with an individual RyR channel produces profound alterations in both channel gating and rates of ion translocation. In the continued presence of the ryanoid the channel fluctuates between periods of normal and modified gating, indicating a reversible interaction of the ligand with its receptor. Unlike the majority of ryanoids, we observe a range of different fractional conductance states of RyR in the presence of 10-O-succinoylryanodol. We demonstrate that 10-O-succinoylryanodol is a very flexible molecule and propose that each fractional conductance state arises from the interaction of a different conformer of the ryanoid molecule with the RyR channel. The probability of channel modification by 10-O-succinoylryanodol is dependent on the transmembrane holding potential. Comparison of the voltage dependence of channel modification by this novel anionic ryanoid with previous data obtained with cationic and neutral ryanoids reveals that the major influence of transmembrane potential on the probability of RyR channel modification by ryanoids results from an alteration in receptor affinity. These investigations also demonstrate that the charge of the ryanoid has a major influence on the rate of association of the ligand with its receptor indicating that ionic interactions are likely to be involved in this reaction.

scholarly journals Interactions of a Reversible Ryanoid (21-Amino-9α-Hydroxy-Ryanodine) with Single Sheep Cardiac Ryanodine Receptor Channels

1998 ◽  
Vol 112 (1) ◽  
pp. 55-69 ◽  
Author(s):  
Bhavna Tanna ◽  
William Welch ◽  
Luc Ruest ◽  
John L. Sutko ◽  
Alan J. Williams
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Binding Site ◽  
Single Channel ◽  
Single Channels ◽  
Open Probability ◽  
Release Channel ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Channel Protein ◽  
High Affinity ◽  
Conductance State

The binding of ryanodine to a high affinity site on the sarcoplasmic reticulum Ca2+-release channel results in a dramatic alteration in both gating and ion handling; the channel enters a high open probability, reduced-conductance state. Once bound, ryanodine does not dissociate from its site within the time frame of a single channel experiment. In this report, we describe the interactions of a synthetic ryanoid, 21-amino-9α-hydroxy-ryanodine, with the high affinity ryanodine binding site on the sheep cardiac sarcoplasmic reticulum Ca2+-release channel. The interaction of 21-amino-9α-hydroxy-ryanodine with the channel induces the occurrence of a characteristic high open probability, reduced-conductance state; however, in contrast to ryanodine, the interaction of this ryanoid with the channel is reversible under steady state conditions, with dwell times in the modified state lasting seconds. By monitoring the reversible interaction of this ryanoid with single channels under voltage clamp conditions, we have established a number of novel features of the ryanoid binding reaction. (a) Modification of channel function occurs when a single molecule of ryanoid binds to the channel protein. (b) The ryanoid has access to its binding site only from the cytosolic side of the channel and the site is available only when the channel is open. (c) The interaction of 21-amino-9α-hydroxy-ryanodine with its binding site is influenced strongly by transmembrane voltage. We suggest that this voltage dependence is derived from a voltage-driven conformational alteration of the channel protein that changes the affinity of the binding site, rather than the translocation of the ryanoid into the voltage drop across the channel.

scholarly journals Synaptic plasticity through activation of GluA3-containing AMPA-receptors

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Maria C Renner ◽  
Eva HH Albers ◽  
Nicolas Gutierrez-Castellanos ◽  
Niels R Reinders ◽  
Aile N van Huijstee ◽  
...  
Keyword(s):  
Ampa Receptors ◽  
Adrenergic Receptors ◽  
Pyramidal Neurons ◽  
Synaptic Potentiation ◽  
High Conductance State ◽  
Hippocampal Synapses ◽  
Β Adrenergic Receptors ◽  
Camp Levels ◽  
Conductance State ◽  
High Conductance

Excitatory synaptic transmission is mediated by AMPA-type glutamate receptors (AMPARs). In CA1 pyramidal neurons of the hippocampus two types of AMPARs predominate: those that contain subunits GluA1 and GluA2 (GluA1/2), and those that contain GluA2 and GluA3 (GluA2/3). Whereas subunits GluA1 and GluA2 have been extensively studied, the contribution of GluA3 to synapse physiology has remained unclear. Here we show in mice that GluA2/3s are in a low-conductance state under basal conditions, and although present at synapses they contribute little to synaptic currents. When intracellular cyclic AMP (cAMP) levels rise, GluA2/3 channels shift to a high-conductance state, leading to synaptic potentiation. This cAMP-driven synaptic potentiation requires the activation of both protein kinase A (PKA) and the GTPase Ras, and is induced upon the activation of β-adrenergic receptors. Together, these experiments reveal a novel type of plasticity at CA1 hippocampal synapses that is expressed by the activation of GluA3-containing AMPARs.

scholarly journals Residual conductance of correlated one-dimensional nanosystems: A numerical approach

2004 ◽  
Vol 39 (1) ◽  
pp. 107-120 ◽  
Author(s):  
R. A. Molina ◽  
P. Schmitteckert ◽  
D. Weinmann ◽  
R. A. Jalabert ◽  
G.-L. Ingold ◽  
...  
Keyword(s):  
Numerical Approach ◽  
One Dimensional ◽  
Residual Conductance

Characterization of Synaptic Conductances and Integrative Properties During Electrically Induced EEG-Activated States in Neocortical Neurons In Vivo

2005 ◽  
Vol 94 (4) ◽  
pp. 2805-2821 ◽  
Author(s):  
Michael Rudolph ◽  
Joe Guillaume Pelletier ◽  
Denis Paré ◽  
Alain Destexhe
Keyword(s):  
Cortical Neurons ◽  
Computational Models ◽  
Input Resistance ◽  
Synaptic Activity ◽  
Intracellular Recordings ◽  
Neocortical Neurons ◽  
Up States ◽  
Conductance State ◽  
Stimulation Of

The activation of the electroencephalogram (EEG) is paralleled with an increase in the firing rate of cortical neurons, but little is known concerning the conductance state of their membrane and its impact on their integrative properties. Here, we combined in vivo intracellular recordings with computational models to investigate EEG-activated states induced by stimulation of the brain stem ascending arousal system. Electrical stimulation of the pedonculopontine tegmental (PPT) nucleus produced long-lasting (≈20 s) periods of desynchronized EEG activity similar to the EEG of awake animals. Intracellularly, PPT stimulation locked the membrane into a depolarized state, similar to the up-states seen during deep anesthesia. During these EEG-activated states, however, the input resistance was higher than that during up-states. Conductance measurements were performed using different methods, which all indicate that EEG-activated states were associated with a synaptic activity dominated by inhibitory conductances. These results were confirmed by computational models of reconstructed pyramidal neurons constrained by the corresponding intracellular recordings. These models indicate that, during EEG-activated states, neocortical neurons are in a high-conductance state consistent with a stochastic integrative mode. The amplitude and timing of somatic excitatory postsynaptic potentials were nearly independent of the position of the synapses in dendrites, suggesting that EEG-activated states are compatible with coding paradigms involving the precise timing of synaptic events.

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