Week 5 ELM 10: Neurotransmitters

Flashcards to review key concepts about receptors and neurotransmitters.

Receptor

Binds an information-carrying molecule (agonist) and passes on the information in a different form (transduction). It changes cell behavior

Agonist

A molecule that binds to a receptor and triggers a response.

Transduction

The process by which a receptor passes on information in a different form, leading to changes in cell behavior.

Ligand-gated ion channel

A type of receptor that opens an ion channel upon binding of a ligand.

G protein-coupled receptor (GPCR)

A type of receptor that activates a G protein upon binding of a ligand, leading to a signaling cascade.

Receptor tyrosine kinase

A type of receptor that phosphorylates tyrosine residues on target proteins upon activation, initiating signaling pathways

Nuclear hormone receptor

A type of receptor located in the nucleus that regulates gene transcription upon binding of a hormone.

G protein

A protein that relays signals from GPCRs to effector proteins.

Second messenger

A small, diffusible molecule produced in response to receptor activation that mediates downstream signaling.

Adenylate cyclase

An enzyme that produces cAMP from ATP.

Phospholipase C

An enzyme that cleaves PIP2 into IP3 and diacylglycerol.

Neurotransmitter

A chemical messenger that transmits signals between neurons.

Monoamines

A class of neurotransmitters including dopamine, serotonin, adrenaline, noradrenaline, and histamine. (Dancing Squirrels Always Nibble Hazelnuts)

Neuropeptides

A class of neurotransmitters including substance P, endorphins, enkephalins, vasopressin, and oxytocin. Purpose: feeling and bonding (Oxy FEELS good, PEPTIDE BONDS) (Silly Penguins Eagerly Explore Kitchen Vigorously Ovulating)

Amino acid neurotransmitters

A class of neurotransmitters including L-glutamate, γ-aminobutyric acid (GABA), and glycine. (Large Giraffes Gracefully Avoid Gymnastics)

Dale’s Principle

A principle stating that a neuron releases only one type of neurotransmitter (though often violated).

Acetylcholinesterase (AChE)

The enzyme responsible for breaking down acetylcholine in the synaptic cleft.

VGluT

Vesicular glutamate transporter, responsible for transporting glutamate into vesicles.

EAAT

Excitatory amino acid transporter, responsible for removing glutamate from the synaptic cleft.

Glutaminase

Enzyme that converts glutamine to glutamate.

Glutamine synthetase

Enzyme that converts glutamate to glutamine.

Acetylcholine receptors: nicotinic vs muscarinic

Ligand-gated ion channels(ionotropic) vs. G protein-coupled receptors (metabotropic)

iGluRs

Ionotropic glutamate receptors. AMPA (quisqualate), kainate, NMDA

NMDA receptor

A type of ionotropic glutamate receptor that is highly permeable to Ca2+ and blocked by Mg2+ at RMP.

mGluR

Metabotropic glutamate receptors.

GABA receptors

Receptors that bind GABA, leading to inhibition of neuronal activity.

GABAA receptor

Ligand gated chloride channels.

GABAB receptor

GPCRs that inhibit voltage gated Ca++ channels, open potassium channels and inhibit adenylyl cyclase.

G Protein- Coupled Receptor structure

7 transmembrane α-helices. They posses an agonist-binding site and a G-protein binding domain

GPCR activation and signal amplification

Agonist bind to GPCR → facilitates the exchange of GDP for GTP on the G protein alpha subunit.

Activated G protein interacts with an effector/target protein

This interaction leads to the production of 2nd messengers, resulting in signal amplification

Enzyme targets produce many 2nd messenger molecules after G-protein coupled receptor activation

Gs (G protein)

• αs subunit

• Target: Adenylate cyclase

• Effect: Increased cAMP

Gi

• αi subunit

• Target: Adenylate cyclase

• Effect: Decreased cAMP

Gq

• αq subunit

• Target: Phospholipase C

• Effect: Increased IP3, diacylglycerol, and cytoplasmic Ca 2+

What are neurotransmitters act on ligand gated ion channels?

Acetylcholine, serotonin, glutamate , GABA

Amines

Dopamine, seretonin, adrenaline, nonadrenaline, histamine, PLUS acetylcholine

A neurotransmitter candidate must meet the following criteria

• Synthesized by the neuron

• Present in synaptic terminal at sufficient concentrations

• Release on (pre) synaptic stimulation

• Exogenous application to postsynaptic receptors produces a physiological response.

• Mechanism exists for its removal from synaptic cleft