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Questions and Answers
Which type of ligand-gated ion channel mediates membrane hyperpolarization?
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?
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?
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?
Which of the following is a characteristic feature of Ionotropic Glutamate Receptors?
What is the typical subunit composition of the Muscle (NM) subtype of nAChR?
What is the typical subunit composition of the Muscle (NM) subtype of nAChR?
Which neurotransmitter activates the Nicotinic Acetylcholine Receptor (nAChR)?
Which neurotransmitter activates the Nicotinic Acetylcholine Receptor (nAChR)?
Propofol is known to modulate which type of ligand-gated ion channel?
Propofol is known to modulate which type of ligand-gated ion channel?
Neurosteroids are capable of influencing the activity of which type of receptor?
Neurosteroids are capable of influencing the activity of which type of receptor?
Ethanol is known to affect which type of ion flow through a ligand-gated channel?
Ethanol is known to affect which type of ion flow through a ligand-gated channel?
What is the main characteristic of ligand-gated ion channels (LGICs) mentioned in the text?
What is the main characteristic of ligand-gated ion channels (LGICs) mentioned in the text?
Which receptor type among the major receptor superfamily utilizes the G-protein-coupled pathway?
Which receptor type among the major receptor superfamily utilizes the G-protein-coupled pathway?
What is the primary function of GABAA receptors?
What is the primary function of GABAA receptors?
Which type of ligand binds to GABAA receptors to activate them?
Which type of ligand binds to GABAA receptors to activate them?
How does the activation of GABAA receptors typically affect cellular function?
How does the activation of GABAA receptors typically affect cellular function?
What type of ions flow into/out of the cell through the activated GABAA receptor channel?
What type of ions flow into/out of the cell through the activated GABAA receptor channel?
How do neurosteroids modulate GABAA receptors?
How do neurosteroids modulate GABAA receptors?
How does propofol modulate GABAA receptors?
How does propofol modulate GABAA receptors?
Why is it important to understand the subunit composition of GABAA receptors?
Why is it important to understand the subunit composition of GABAA receptors?
What distinguishes synaptic GABAA receptors from extrasynaptic ones?
What distinguishes synaptic GABAA receptors from extrasynaptic ones?
Which type of GABAA receptors typically contain a δ-subunit and α4, α5, or α6 subunits?
Which type of GABAA receptors typically contain a δ-subunit and α4, α5, or α6 subunits?
Which subunits are generally formed from two α-subunits, two β-subunits, and either a γ- or δ-subunit in GABAA receptors?
Which subunits are generally formed from two α-subunits, two β-subunits, and either a γ- or δ-subunit in GABAA receptors?
Which drug is preferentially modulated by extrasynaptic GABAA receptors?
Which drug is preferentially modulated by extrasynaptic GABAA receptors?
Where are synaptic GABAA receptors typically located?
Where are synaptic GABAA receptors typically located?
Which of the following is NOT a ligand-gated ion channel receptor?
Which of the following is NOT a ligand-gated ion channel receptor?
What ions predominantly flow through GABAA receptor channels upon activation?
What ions predominantly flow through GABAA receptor channels upon activation?
Which subunit classes are cloned for GABAA receptors according to the text?
Which subunit classes are cloned for GABAA receptors according to the text?
What is the key functional role of the NN subtype of GABAA receptors?
What is the key functional role of the NN subtype of GABAA receptors?
Which drugs allosterically modulate GABAA receptors according to the text?
Which drugs allosterically modulate GABAA receptors according to the text?
What plays a key role as the main inhibitory transmitter in the brain according to the text?
What plays a key role as the main inhibitory transmitter in the brain according to the text?
Describe the subclassification basis of ligand-gated ion channels.
Describe the subclassification basis of ligand-gated ion channels.
What are the key characteristic features of the major ligand-gated ion channel families?
What are the key characteristic features of the major ligand-gated ion channel families?
Describe the molecular structure, subtypes, cellular expression, and functional role of nicotinic acetylcholine receptors (nAChRs).
Describe the molecular structure, subtypes, cellular expression, and functional role of nicotinic acetylcholine receptors (nAChRs).
Describe the molecular structure, subtypes, cellular expression, and functional role of GABAA receptors (GABAARs).
Describe the molecular structure, subtypes, cellular expression, and functional role of GABAA receptors (GABAARs).
What are the unique features/characteristics of the ligand-gated ion channel superfamily?
What are the unique features/characteristics of the ligand-gated ion channel superfamily?
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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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