Comparative models of GABAA receptors based on homologous pentameric ligand-gated ion channels co-crystallized with ligands

2013 ◽  
Vol 1 (Suppl. 1) ◽  
pp. A1.26
Author(s):  
Roman V. Feldbauer
Keyword(s):  
Ion Channels ◽  
Gabaa Receptors ◽  
Gated Ion Channels ◽  
Ligand Gated Ion Channels

Effects of Gaseous Anesthetics Nitrous Oxide and Xenon on Ligand-gated Ion Channels

2000 ◽  
Vol 93 (4) ◽  
pp. 1095-1101 ◽  
Author(s):  
Tomohiro Yamakura ◽  
R. Adron Harris
Keyword(s):  
Nitrous Oxide ◽  
Ion Channels ◽  
Nmda Receptors ◽  
Glutamate Receptors ◽  
Gabaa Receptors ◽  
Receptor Type ◽  
Gamma Aminobutyric Acid ◽  
General Anesthetics ◽  
Gated Ion Channels ◽  
Ligand Gated Ion Channels

Background Ligand-gated ion channels are considered to be potential general anesthetic targets. Although most general anesthetics potentiate the function of gamma-aminobutyric acid receptor type A (GABAA), the gaseous anesthetics nitrous oxide and xenon are reported to have little effect on GABAA receptors but inhibit N-methyl-d-aspartate (NMDA) receptors. To define the spectrum of effects of nitrous oxide and xenon on receptors thought to be important in anesthesia, the authors tested these anesthetics on a variety of recombinant brain receptors. Methods The glycine, GABAA, GABA receptor type C (GABAC), NMDA, alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA), kainate, 5-hydroxytryptamine3 (5-HT3), and nicotinic acetylcholine (nACh) receptors were expressed in Xenopus oocytes and effects of nitrous oxide and xenon, and as equipotent concentrations of isoflurane and ethanol, were studied using the two-electrode voltage clamp. Results Nitrous oxide (0.58 atmosphere [atm]) and xenon (0.46 atm) exhibited similar effects on various receptors. Glycine and GABAA receptors were potentiated by gaseous anesthetics much less than by isoflurane, whereas nitrous oxide inhibited GABAC receptors. Glutamate receptors were inhibited by gaseous anesthetics more markedly than by isoflurane, but less than by ethanol. NMDA receptors were the most sensitive among glutamate receptors and were inhibited by nitrous oxide by 31%. 5-HT3 receptors were slightly inhibited by nitrous oxide. The nACh receptors were inhibited by gaseous and volatile anesthetics, but ethanol potentiated them. The sensitivity was different between alpha4beta2 and alpha4beta4 nACh receptors; alpha4beta2 receptors were inhibited by nitrous oxide by 39%, whereas alpha4beta4 receptors were inhibited by 7%. The inhibition of NMDA and nACh receptors by nitrous oxide was noncompetitive and was slightly different depending on membrane potentials for NMDA receptors, but not for nACh receptors. Conclusions Nitrous oxide and xenon displayed a similar spectrum of receptor actions, but this spectrum is distinct from that of isoflurane or ethanol. These results suggest that NMDA receptors and nACh receptors composed of beta2 subunits are likely targets for nitrous oxide and xenon.

Intravenous Anesthetics Differentially Modulate Ligand-gated Ion Channels

2000 ◽  
Vol 92 (5) ◽  
pp. 1418-1425 ◽  
Author(s):  
Pamela Flood ◽  
Matthew D. Krasowski
Keyword(s):  
Ion Channels ◽  
Gabaa Receptor ◽  
Nicotinic Acetylcholine Receptors ◽  
Gabaa Receptors ◽  
Xenopus Laevis Oocytes ◽  
Intravenous Anesthetics ◽  
Relevant Concentration ◽  
High Concentrations ◽  
Gated Ion Channels ◽  
Ligand Gated Ion Channels

Background Heteromeric neuronal nicotinic acetylcholine receptors (nAChRs) are potently inhibited by volatile anesthetics, but it is not known whether they are affected by intravenous anesthetics. Ketamine potentiates gamma-aminobutyric acid type A (GABAA) receptors at high concentrations, but it is unknown whether there is potentiation at clinically relevant concentrations. Information about the effects of intravenous anesthetics with different behavioral profiles on specific ligand-gated ion channels may lead to hypotheses as to which ion channel effect produces a specific anesthetic behavior. Methods A heteromeric nAChR composed of alpha4 and beta4 subunits was expressed heterologously in Xenopus laevis oocytes. Using the two-electrode voltage clamp technique, peak ACh-gated current was measured before and during application of ketamine, etomidate, or thiopental. The response to GABA of alpha1beta2gamma2s GABAA receptors expressed in human embryonic kidney cells and Xenopus oocytes was compared with and without coapplication of ketamine from 1 microm to 10 mm. Results Ketamine caused potent, concentration-dependent inhibition of the alpha4beta4 nAChR current with an IC50 of 0.24 microm. The inhibition by ketamine was use-dependent; the antagonist was more effective when the channel had been opened by agonist. Ketamine did not modulate the alpha1beta2gamma2s GABAA receptor response in the clinically relevant concentration range. Thiopental caused 27% inhibition of ACh response at its clinical EC50. Etomidate did not modulate the alpha4beta4 nAChR response in the clinically relevant concentration range, although there was inhibition at very high concentrations. Conclusions The alpha4beta4 nAChR, which is predominantly found in the central nervous system (CNS), is differentially affected by clinically relevant concentrations of intravenous anesthetics. Ketamine, commonly known to be an inhibitor at the N-methyl-D-aspartate receptor, is also a potent inhibitor at a central nAChR. It has little effect on a common CNS GABAA receptor in a clinically relevant concentration range. Interaction between ketamine and specific subtypes of nAChRs in the CNS may result in anesthetic behaviors such as inattention to surgical stimulus and in analgesia. Thiopental causes minor inhibition at the alpha4beta4 nAChR. Modulation of the alpha4beta4 nAChR by etomidate is unlikely to be important in anesthesia practice based on the insensitivity of this receptor to clinically used concentrations.

Physiology and biophysics of plant ligand-gated ion channels

Plant Biology ◽  
2010 ◽  
Vol 12 ◽  
pp. 80-93 ◽  
Author(s):  
P. Dietrich ◽  
U. Anschütz ◽  
A. Kugler ◽  
D. Becker
Keyword(s):  
Ion Channels ◽  
Gated Ion Channels ◽  
Ligand Gated Ion Channels

scholarly journals Molecular Simulations of Hydrophobic Gating of Pentameric Ligand Gated Ion Channels: Insights into Water and Ions

2021 ◽  
Vol 125 (4) ◽  
pp. 981-994
Author(s):  
Shanlin Rao ◽  
Gianni Klesse ◽  
Charlotte I. Lynch ◽  
Stephen J. Tucker ◽  
Mark S. P. Sansom
Keyword(s):  
Ion Channels ◽  
Molecular Simulations ◽  
Gated Ion Channels ◽  
Ligand Gated Ion Channels

Ligand-gated ion channels as targets of neuroactive insecticides

2021 ◽  
Author(s):  
Makoto Ihara
Keyword(s):  
Ion Channels ◽  
Molecular Mechanisms ◽  
Functional Expression ◽  
X Ray ◽  
Acetylcholine Binding Protein ◽  
Site Selectivity ◽  
Future Drug ◽  
Cl Channels ◽  
Gated Ion Channels ◽  
Ligand Gated Ion Channels

Abstract The Cys-loop superfamily of ligand-gated ion channels (Cys-loop receptors) is one of the most ubiquitous ion channel families in vertebrates and invertebrates. Despite their ubiquity, they are targeted by several classes of pesticides, including neonicotinoids, phenylpyrazols, and macrolides such as ivermectins. The current commercialized compounds have high target site selectivity, which contributes to the safety of insecticide use. Structural analyses have accelerated progress in this field; notably, the X-ray crystal structures of acetylcholine binding protein and glutamate-gated Cl channels revealed the details of the molecular interactions between insecticides and their targets. Recently, the functional expression of the insect nicotinic acetylcholine receptor (nAChR) has been described, and detailed evaluations using the insect nAChR have emerged. This review discusses the basic concepts and the current insights into the molecular mechanisms of neuroactive insecticides targeting the ligand-gated ion channels, particularly Cys-loop receptors, and presents insights into target-based selectivity, resistance, and future drug design.

Sign in / Sign up

Export Citation Format

Share Document