P2X Receptors Overview

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Questions and Answers

What is the structural composition of P2X receptors?

Trimeric, composed of three protein subunits (correct)
Dimeric, composed of two protein subunits
Tetrameric, composed of four protein subunits
Monomeric, composed of one protein subunit

Which ion is P2X receptors NOT commonly permeable to?

Ca2+
Mg2+ (correct)
K+
Na+

What distinguishes P2X receptors from cys-loop and ionotropic glutamate receptors in terms of oligomeric structure?

They exclusively form hetero-oligomeric structures
They are always monomeric in structure
They can be either homo-oligomeric or hetero-oligomeric (correct)
They can only form homo-oligomeric structures

How many subunits of P2X receptors have been identified?

Seven (A) Signup and view all the answers

What is one of the primary challenges in drug development targeting P2X receptors?

The complexity of their oligomeric structures (B) Signup and view all the answers

Which physiological function is primarily associated with P2X1 receptors?

Urinary bladder contraction (B) Signup and view all the answers

Which of the following antagonists is known to act on multiple P2X receptors?

Suramin (B) Signup and view all the answers

In which tissues are P2X6 receptors predominantly expressed?

B cells (A) Signup and view all the answers

What physiological function do P2X7 receptors primarily influence?

Inflammation (B) Signup and view all the answers

How are P2X receptors modulated under physiological conditions?

By pH changes (C) Signup and view all the answers

What is the basic structure of P2X receptors?

A trimer made of three subunits surrounding an ion channel (B) Signup and view all the answers

Which of the following statements accurately describes P2X receptor subunits?

All two transmembrane domains from each subunit contribute to the channel pore. (C) Signup and view all the answers

In what way may native P2X receptors exist?

Either as homo-oligomeric or hetero-oligomeric receptors (D) Signup and view all the answers

What role does ATP play in P2X receptors?

ATP gates the ion channels of P2X receptors, mediating excitatory neurotransmission. (B) Signup and view all the answers

What distinguishes P2Y receptors from P2X receptors?

P2Y receptors are G-protein-coupled receptors that bind ADP and adenosine. (A) Signup and view all the answers

What is the primary cation that can permeate through 5-HT3 receptors?

Na+ (C) Signup and view all the answers

Which of the following is NOT a class of positive allosteric modulators of GABA-A receptors?

Amygdala antagonists (A) Signup and view all the answers

In which system are 5-HT3 receptors primarily located?

All of the above (D) Signup and view all the answers

What two elements are 5-HT3 receptors permeable to, besides sodium?

K+ and Ca2+ (C) Signup and view all the answers

Which drug class is known to evoke sedation at high doses through GABA-A receptor modulation?

Neurosteroids (B) Signup and view all the answers

What is the primary role of AChE in synaptic activity?

It degrades acetylcholine to terminate its action. (D) Signup and view all the answers

Which of the following actions are associated with drugs that increase synaptic GABA concentrations?

Anti-epileptic effects (A) Signup and view all the answers

What mechanism of action do 5-HT3 receptor antagonists serve primarily in medical treatment?

Acting as anti-emetics (C) Signup and view all the answers

Which ionotropic glutamate receptor is primarily associated with fast synaptic excitation and has a high permeability to Na+ and K+?

AMPA receptors (D) Signup and view all the answers

What is a significant characteristic of NMDA receptors in terms of their pharmacological manipulation?

Open-channel blockers like ketamine can inhibit their function. (D) Signup and view all the answers

Which receptor family is noted for its limited permeability to Ca2+ and may lead to cell death when overactive?

Ionotropic glutamate receptors (B) Signup and view all the answers

The physiological modes of action of P2X receptors are characterized by what significant challenge?

The difficulty in identifying selective ligands for them. (D) Signup and view all the answers

What general physiological function do ionotropic glutamate receptors serve in the CNS?

Facilitating synaptic transmission and excitation. (A) Signup and view all the answers

P2X receptors are found in multiple locations in the body. Which of the following is NOT one of their general tissue distributions?

Cardiac muscle (C) Signup and view all the answers

What is a common property shared by both NMDA and AMPA receptors?

Both are non-selective cation channels. (C) Signup and view all the answers

What is a potential outcome of the over-activity of ionotropic glutamate receptors in the brain?

Cell death due to excitotoxicity. (C) Signup and view all the answers

Study Notes

P2X Receptors

P2X receptors are ligand-gated ion channels that are activated by ATP.
They are trimeric, composed of three protein subunits.
P2X receptors are permeable to Na+, K+, and Ca2+ ions, and in some cases Cl-.
They can be either homo-oligomeric or hetero-oligomeric.
There are 7 identified P2X receptor subunits: P2X1-7.
P2X receptors are involved in a variety of physiological processes, including synaptic transmission, cardiac function, gut motility, kidney function, vascular tone, nociception, apoptosis, and immune responses.
P2X receptors are expressed in a variety of tissues, including the nervous system, smooth muscle, and skeletal muscle.
P2X receptors are allosterically modulated by changes in pH.

P2X Receptor Subtypes & Functions

P2X1 receptors are found in smooth muscle and the urinary bladder, and are involved in urinary bladder contraction.
P2X2, P2X3, and P2X2/3 receptors are found in the nervous system, specifically sensory neurons, and are involved in taste perception.
P2X4 receptors are found in the central nervous system, and are involved in neuroinflammation.
P2X5 receptors are found in B cells and T cells, and are involved in inflammation and chloride conductance.
P2X6 receptors are found in B cells, and are involved in pro-inflammatory immune responses.
P2X7 receptors are found in a wide variety of tissues, including the heart, liver, skeletal muscle, pancreas, thymus, tonsils, monocytes, macrophages, and osteoclasts, and are involved in inflammation.

P2X Receptor Pharmacology

Agonists for P2X receptors include ATP, αβ-me-ATP, and BzATP.
Antagonists for P2X receptors include suramin, an anti-parasitic drug, which is active at P2X1, P2X2, P2X3, and P2X5 receptors.
Drug development for P2X receptors has been challenging due to their widespread expression and diverse physiological roles.
There is a lack of selective ligands for P2X receptors.

Acid-Sensing Ion Channels (ASICs)

ASICs are a family of ligand-gated ion channels that are activated by protons (H+).
ASICs are involved in a variety of physiological processes, including pain perception, neuronal excitability, and neuronal injury.
ASICs belong to the same superfamily of proteins as the P2X receptors and cys-loop receptors.

Comparison of P2X Receptors and ASICs

Both P2X receptors and ASICs are cation permeable channels, however, their activation mechanisms differ.
P2X channels are opened by the binding of ATP, while ASICs are opened by a decrease in pH.
P2X receptors play roles in synaptic transmission, while ASICs are more involved in pain perception and neuronal excitability.

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Description

Explore the fascinating world of P2X receptors, ligand-gated ion channels activated by ATP. This quiz delves into their structure, subtypes, physiological roles, and the impact they have on various bodily functions. Gain insights into their diverse expression in tissues and their modulation by pH.