ligand gated ion channels 30

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Questions and Answers

Which type of ligand-gated ion channel mediates membrane hyperpolarization?

nAChR

GABAAR (correct)

AMPA receptor

5-HT3R

How many subunits typically make up a Cys-loop receptor in the LGIC family?

Four

Two

Three

Five (correct)

Which type of ion does GABAAR allow to flow through the open channel?

Sodium ions

Calcium ions

Potassium ions

Chloride ions (correct)

Which of the following is a characteristic feature of Ionotropic Glutamate Receptors?

Non-selective cation channels Signup and view all the answers

What is the typical subunit composition of the Muscle (NM) subtype of nAChR?

2α1, β1, δ, & γ/ε subunits Signup and view all the answers

Which neurotransmitter activates the Nicotinic Acetylcholine Receptor (nAChR)?

Acetylcholine Signup and view all the answers

Propofol is known to modulate which type of ligand-gated ion channel?

GABAAR Signup and view all the answers

Neurosteroids are capable of influencing the activity of which type of receptor?

GABAAR Signup and view all the answers

Ethanol is known to affect which type of ion flow through a ligand-gated channel?

Chloride ions Signup and view all the answers

What is the main characteristic of ligand-gated ion channels (LGICs) mentioned in the text?

Incorporate extracellular ligand-binding sites Signup and view all the answers

Which receptor type among the major receptor superfamily utilizes the G-protein-coupled pathway?

GABAA receptors Signup and view all the answers

What is the primary function of GABAA receptors?

Inhibit neurotransmission Signup and view all the answers

Which type of ligand binds to GABAA receptors to activate them?

GABA Signup and view all the answers

How does the activation of GABAA receptors typically affect cellular function?

Inhibits neuronal activity Signup and view all the answers

What type of ions flow into/out of the cell through the activated GABAA receptor channel?

Calcium and chloride ions Signup and view all the answers

How do neurosteroids modulate GABAA receptors?

By enhancing GABAergic inhibition Signup and view all the answers

How does propofol modulate GABAA receptors?

By enhancing receptor response to GABA Signup and view all the answers

Why is it important to understand the subunit composition of GABAA receptors?

It influences the pharmacological properties of the receptor. Signup and view all the answers

What distinguishes synaptic GABAA receptors from extrasynaptic ones?

Different cellular expression pattern. Signup and view all the answers

Which type of GABAA receptors typically contain a δ-subunit and α4, α5, or α6 subunits?

Extrasynaptic receptors Signup and view all the answers

Which subunits are generally formed from two α-subunits, two β-subunits, and either a γ- or δ-subunit in GABAA receptors?

α1 and β2 subunits Signup and view all the answers

Which drug is preferentially modulated by extrasynaptic GABAA receptors?

Propofol Signup and view all the answers

Where are synaptic GABAA receptors typically located?

Within the synaptic cleft Signup and view all the answers

Which of the following is NOT a ligand-gated ion channel receptor?

Neuronal subtype receptor Signup and view all the answers

What ions predominantly flow through GABAA receptor channels upon activation?

$Cl^-$ ions Signup and view all the answers

Which subunit classes are cloned for GABAA receptors according to the text?

$eta$ and $ ho$ subunits Signup and view all the answers

What is the key functional role of the NN subtype of GABAA receptors?

Modulation of transmitter release Signup and view all the answers

Which drugs allosterically modulate GABAA receptors according to the text?

Benzodiazepines & Alcohol Signup and view all the answers

What plays a key role as the main inhibitory transmitter in the brain according to the text?

GABA (Gamma-aminobutyric acid) Signup and view all the answers

Describe the subclassification basis of ligand-gated ion channels.

The subclassification is based on the type of ligand that binds to the receptor. Signup and view all the answers

What are the key characteristic features of the major ligand-gated ion channel families?

The key characteristic features include molecular structure, subtypes, cellular expression, and functional roles. Signup and view all the answers

Describe the molecular structure, subtypes, cellular expression, and functional role of nicotinic acetylcholine receptors (nAChRs).

Nicotinic acetylcholine receptors are pentameric ligand-gated ion channels, expressed in the central and peripheral nervous systems, and play a role in excitatory neurotransmission. Signup and view all the answers

Describe the molecular structure, subtypes, cellular expression, and functional role of GABAA receptors (GABAARs).

GABAA receptors are pentameric ligand-gated ion channels, expressed in the brain, and primarily function as inhibitory neurotransmitters. Signup and view all the answers

What are the unique features/characteristics of the ligand-gated ion channel superfamily?

The ligand-gated ion channel superfamily consists of multimeric integral membrane proteins with extracellular ligand-binding sites and a central transmembrane ion-permeable channel/pore. Signup and view all the answers

Study Notes

Ligand-Gated Ion Channels (LGICs)

LGICs are a type of receptor that allows ions to flow into the cell when a ligand binds to it
Classified into two main categories: excitatory (cation-selective) and inhibitory (anion-selective) ion channels

Excitatory LGICs

Mediate influx of cations (e.g. Na+, Ca++) into the cell
Cause membrane depolarization
Examples: nAChR, 5-HT3R, ionotropic glutamate receptors (NMDA, AMPA, and kainate), and P2X receptors

Inhibitory LGICs

Mediate influx of anions (e.g. Cl-) into the cell
Cause membrane hyperpolarization
Examples: GABAAR and glycine receptors

Cys-loop Receptor Family

Characterized by a disulfide Cys-loop in the extracellular domain
Examples: nAChR, 5-HT3R, GABAAR, and glycine receptors
Subunits share a common structure with a large extracellular domain, 4 transmembrane α-helices, and a short extracellular C-terminal domain

Nicotinic Acetylcholine Receptor (nAChR)

Activated endogenously by acetylcholine
Also activated by nicotine
Occurs in the central and peripheral nervous system
Mediates fast synaptic transmission in the nervous system and at the somatic neuromuscular junction (NMJ)
Plays key roles in controlling skeletal muscle contraction, and modulation of neuronal excitability and integration, gene expression, learning and memory formation, and neuroprotection

Molecular Structure and Function of nAChR

Pentameric complexes composed of 5 subunits
17 nAChR subunits cloned: α1-α10, β1-β4, γ, δ, and ε
Subunits co-assemble to form functional homo- or heteropentameric receptors
Muscle (NM) subtype typically comprises 2α1, β1, δ, and γ/ε subunits
Neuronal (NN) subtype typically comprises 2α and 3β subunits (hetero-pentamers) or 5α7 subunits (homo-pentamers)

GABAAR Receptor

Activated endogenously by GABA
Occurs widely in the CNS
Mediates fast (phasic) and slow (tonic) neuronal inhibition
Plays key roles in controlling feeding behavior, circadian rhythm, sleep-wake cycle, vigilance, learning, and memory
Implicated in anxiety/sleep disorders, depression, mania, autism, psychosis, and alcoholism

Allosteric Modulation of GABAAR

GABAARs have multiple ligand binding sites
Allosteric modulators bind to specific binding sites on GABAARs and enhance or potentiate the effects of GABA
Examples: benzodiazepines, barbiturates, neurosteroids, general anesthetics, and alcohol

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Description

Test your knowledge on neuronal subtypes and receptor superfamilies in the Central Nervous System. Explore key functional roles including modulation of transmitter release, gene expression, cognition, and neuroprotection. Focus on the role of Muscle Type nAChRs in skeletal muscle contraction.