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Author Topic: An Overview of ION Channels (the mechanism behinds drugs such as GABApentinoids)  (Read 985 times)

Offline Chip (OP)

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source: https://www.sciencedirect.com/topics/neuroscience/ion-channels

This information is only a bunch of their excerpts so check the source link for the full text. Anybody
using Gabapentinoids would know the feeling of the Calcium Channel ION Blockers (too much may even kill you so go easy when fucken around as tolerance develops rapidly, also).

Just ask me, my sleep has been trashed by overuse !

ION channels have a massive influence on us and make for interesting areas for Psychiatry, i think.

Note that some information has been duplicated due to differing versions as theories evolve.

The following are excerpts of excerpts so you know what to do to see the originals ...

Ion Channels

General Introduction

Ion channels are selective “pores” for the passage of ions across the hydrophobic barrier of the plasma membrane.

The physiological activity of a number of cell types is dependent upon their ability to organize integral membrane proteins and, in particular, ion channels, into functionally specialized domains of the plasma membrane.

This organization underlies a wide range of cellular functions including the propagation and integration of electrical signals in the nervous and muscular system by “excitable” membranes.

Ion channels are protein molecules that span across the cell membrane allowing the passage of ions from one side of the membrane to the other.

They have an aqueous pore, which becomes accessible to ions after a conformational change in the protein structure that causes the ion channel to open.

Ion channels are selective meaning that they only allow certain ions to pass through them, and they play critical roles in controlling neuronal excitability.

Ion channels are divided into those that are:

1. opened by changes in membrane potential
2. voltage-gated ion channels
3. ion channels that are opened by the binding of a ligand, such as a hormone or a neurotransmitter, ligand-gated ion channels.

We introduce both voltage-gated and ligand-gated ion channels that are abundantly expressed within the central nervous system and the peripheral nervous system.

Here, we discuss their roles in neurological disorders and introduce some common clinically used drugs that target ion channels as a means of treatment.

Introduction

Ion channels are macromolecular protein complexes spanning the lipid bilayer of the cell membrane Hille (2001).

Up to 30% of the energy generated by the cell is used to maintain a concentration gradient of ions across the membrane.

Ion channels are able to use this energy store. Small conformational changes in the channel induce a transition from the closed to the open state, allowing up to 10 million ions per second to flow into or out of the cell.

Usually ion channels are classified according to a specific type of ion which passes the channel; however, some are less selective. The main stimuli for channel opening are either changes in the membrane potential or binding of extracellular ligands or intracellular second messengers.

The ion channel proteomeWiki has an extraordinary high number of members Yu and Catterall (2004).

It includes voltage-gated sodium and calcium channelsWiki, voltage-sensitive potassium channels, chloride channels, cyclic nucleotide-gated channels, hyperpolarization activated channels, ionotropic glutamate receptors, nicotinic acetylcholine receptors, GABA-A receptors, glycine receptors, transient receptor potential channels, amiloride sensitive channels, ryanodine receptors and IP-3 Receptors Biel et al (2002) Catterall (2000) Hofmann et al (1999) Littleton and Ganetzky (2000) Ramsey et al (2006).

Ion Channels

Sven Moosmang, Franz Hofmann, in xPharm: The Comprehensive Pharmacology Reference, 2009

Introduction

Ion channels are macromolecular protein complexes spanning the lipid bilayer of the cell membrane Hille (2001). Up to 30% of the energy generated by the cell is used to maintain a concentration gradient of ions across the membrane. Ion channels are able to use this energy store. Small conformational changes in the channel induce a transition from the closed to the open state, allowing up to 10 million ions per second to flow into or out of the cell. Usually ion channels are classified according to a specific type of ion which passes the channel; however, some are less selective. The main stimuli for channel opening are either changes in the membrane potential or binding of extracellular ligands or intracellular second messengers.

The ion channel proteome has an extraordinary high number of members Yu and Catterall (2004). It includes voltage-gated sodium and calcium channels, voltage-sensitive potassium channels, chloride channels, cyclic nucleotide-gated channels, hyperpolarization activated channels, ionotropic glutamate receptors, nicotinic acetylcholine receptors, GABA-A receptors, glycine receptors, transient receptor potential channels, amiloride sensitive channels, ryanodine receptors and IP-3 Receptors Biel et al (2002) Catterall (2000) Hofmann et al (1999) Littleton and Ganetzky (2000) Ramsey et al (2006).

Read the full chapter at the source link to the full text

Molecular Mechanisms of Drug Actions

Catherine Litalien, Pierre Beaulieu, in Pediatric Critical Care (Fourth Edition), 2011

Ion Channels

Ion channels are molecular machines that serve as principal integrating and regulatory devices for the control of cellular excitability. Different types of ion channels have been described: channels responding to electrical (voltage-dependent ion channels), mechanical, or chemical (ligand-gated ion channels) stimuli; ion channels controlled by phosphorylation/dephosphorylation mechanisms; and G protein–gated ion channels. Most ion channels are of the voltage-dependent type and consist mainly of Na+, K+, and Ca2+ channels. Drugs can affect ion channel function directly by binding to the channel protein and altering its function or indirectly through G proteins and other intermediates. Lidocaine is a good example of a drug that directly affects voltage-gated Na+ channels by blocking the channel and thus Na+ entry into the cell. Channel-linked receptors (ligand-gated ion channels) are discussed below.

Circadian Regulation of Ion Channels in Photoreceptors☆
G.Y.-P. Ko, in Reference Module in Neuroscience and Biobehavioral Psychology, 2017

Ion Channels in Photoreceptors

Ion channels are macromolecular pores that allow charged ions to move across cell membranes and contribute to the excitability of neurons and muscles.

Electrical signals are generated and modulated as different types of channels open and close in response to neurotransmitters, hormones, membrane potential changes, mechanical forces, and other agents.

There are two major classes of ion channels: voltage-gatedWiki and ligand-gatedWiki ion channels. Voltage-gated ion channels open or close their pores in response to membrane potential changes.

Ligand-gated ion channels gate occur on movement and generate electrical signals in response to specific chemicals such as neurotransmitters or cyclic-nucleotides.

Vertebrate photoreceptorsWiki are highly polarized, so the distribution of ion channels on the plasma membrane is spatially compartmentalized.

The outer segment membrane is concentrated with cGMP-gated (the cGMP-gated channel of the rod photoreceptor cell plays a key role in phototransduction by controlling the flow of Na+ and Ca2+ into the outer segment) ion channels that are closed by light, whereas the inner segment and the synaptic terminal are furnished with at least six different ion channels.

These six ion channels include: (1) cGMP-gated ion channels; (2) L-type voltage-gated calcium channels; (3) calcium-activated potassium (KCa) channels; (4) non-inactivating voltage-gated potassium channels; (5) calcium-activated chloride channels; (6) hyperpolarization-activated and cyclic nucleotide-modulated cation channels.

Thus far, cGMP-gated ion channels and L-type voltage-gated calcium channels have been studied the most especially in regards to their gating properties and physiological functions in photoreceptors. Both ion channels are under circadian control. In the following, the circadian regulation of cGMP-gated ion channels and L-type voltage-gated calcium channels will be reviewed in detail.

Computational Modeling of Cardiac K+ Channels and Channelopathies
L.R. Perez, ... C.E. Clancy, in Ion Channels in Health and Disease, 2016

Sophisticated ion channel models have even been developed that account for various genetic defects that alter the behavior of ion channels.

These complex ion channel representations have been incorporated into numerous cardiac model “cells” from multiple species.

The cellular level models have been widely replicated and coupled, creating mathematical representations of cardiac tissue in one, two, or three dimensions, with incorporation of complex anatomical heterogeneities including anisotropy, structural features, and distinct cells with specifically associated electrophysiological characteristics.

Experimental data are also increasingly available describing the fundamental structure of ion channels. For this reason, modeling and simulation studies at the molecular scale are now possible and are beginning to reveal fundamental biological principles and structural mechanisms of ion channel functional changes.

The following are excerpts of excerpts so you know what to do to see the originals ...
« Last Edit: June 17, 2019, 03:12:27 PM by Chip »
I do not condone or support any illegal activities. All information is for theoretical discussion and wonder.
All activities discussed are considered fictional and hypothetical. Information of all discussion has been derived from online research and in the spirit of personal Freedom.

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