Neurotransmitters and Receptors Flashcards
A classical neurotransmitter is released from the _____ side and binds to the _____ side.
Pre-synaptic
Post-synaptic
A classical neurotransmitter is regulated when pre-synaptic ____ binds to _____, causing the release of ____.
Ca+2
Synaptotagmin
Vesicles
A classical neurotransmitter functions by binding the _____ side and causing a _____.
Post-synaptic
Change
A small molecule neurotransmitter is made and put into synaptic vesicles near where?
Synapse
The vesicles used to contain small molecule neurotransmitters are what size and opaqueness?
Small, clear
Are small molecules released at the active zone?
Yes
Peptide neurotransmitters are made where from what?
Cell body
Proteins
After being packaged into vesicles, what happens to the proteins used to make peptide neurotransmitters?
They are processed into peptides
Where are peptide neurotransmitters released relative to the active zone?
Near, but not at active zone
The vesicles that contain peptide neurotransmitters are called ___ ___ because they appear ____ and are ____ than the vesicles of small molecules.
Dense core
Dark
Bigger
During low frequency stimulation, are small molecule, peptide, or both neurotransmitters released by the pre-synaptic neuron?
Small molecule
During high frequency stimulation, are small molecule, peptide, or both neurotransmitters released by the pre-synaptic neuron? Why is this the case?
Both
Ca+2 accumulated on pre-synaptic side diffuses to cause peptide neurotransmitter release
2 reasons why releasing both small molecule and peptide neurotransmitters would be useful (signals sent, distance from synapse)
Differences in signal sent between low and high frequency
Release from farther away from synapse
Small molecule neurotransmitters include what 4 categories?
Acetylcholine
Amino acids
Biogenic amines
Purines
What are 3 small molecule amino acid neurotransmitters?
Glutamate
GABA
Glycine
What are 3 classes of small molecule biogenic amine neurotransmitters?
Catecholamines (dopamine, norepinephrine, epinephrine)
Indoleamine (serotonin)
Imidazoleamine (histamine)
What type of purine is a small molecule neurotransmitter?
ATP
Neuropeptide neurotransmitters include what subcategory?
Opioids
3 types of unconventional neurotransmitters
Adenosine
Endocannabinoids
NO
2 types of neurotransmitter receptors
Ionotropic
Metabotropic
Ionotropic neurotransmitter receptors are also called what? What happens when a neurotransmitter binds to it?
Ligand-gated receptor
Ion channel opens
Metabotropic neurotransmitter receptors are also called what? What happens when a neurotransmitter binds to it?
G protein-coupled receptors
Binding of neurotransmitter triggers interaction with G-protein, which triggers intracellular signaling, which may affect ion channels
8 types of ligand-gated receptors
nACh (nicotinic acetylcholine) AMPA NMDA Kainate GABA Glycine Serotonin (5-HT 3 type) Purines (P2X type)
About how many subunits required to make a functional ligand-gated receptor? Is the functional channel made up of the same or different type of subunits?
4-5
Different (heterotetramer or pentamer)
How are AMPA receptor subunits designated?
GluA#
How are NMDA receptor subunits designated?
GluN#
How are kainate receptor subunits designated?
GluK#
What 4 neurotransmitters have no ion channel receptors?
Dopamine
Epinephrine
Norepinephrine
Histamine
A ligand-gated receptor must have at least some domains that are in what 3 places relative to the plasma membrane of the cell?
Transmembrane
Extracellular
Intracellular
In a ligand-gated receptor, what type of secondary structure would comprise a transmembrane domain?
Alpha helices
In a ligand-gated receptor, what type of structure might comprise an extracellular domain?
Pore loop
On a ligand-gated receptor, where do most ligands bind relative to the cell?
Extracellular side (can’t cross plasma membrane)
In a ligand-gated receptor, what is different between closed vs open (ligand binding causes what to happen to receptor)?
Conformation of receptor
An antagonist binding a ligand-gated receptor has what effect on its conformation?
Closes it
8 different types of metabotropic receptors
Muscarinic Glutamate GABA B Dopamine Adrenergic Histamine Serotonin Purines (Adenosine and P2Y)
All G protein-coupled receptors can function with ____ subunit(s). Some act as ______ (same or different subunit type, number of subunits together).
1 (monomer)
Heterodimers
Type of neurotransmitter for which there is no G protein-coupled receptor
Glycine
Does a G protein-coupled receptor have a pore? Why or why not?
No- it isn’t an ion channel
How many transmembrane helices per G protein-coupled receptor?
7
What side of the G protein-coupled receptor (extra- or intra-cellular) interacts with the G protein? On which side does the ligand bind?
Intracellular
Extracellular
What happens to the G protein-coupled receptor when the ligand binds to it? What does it then bind to? What happens to the G protein?
G protein-coupled receptor undergoes conformational change
G protein
Gets activated
How many subunits does a G protein have?
3 (trimeric G protein)
The ___ subunit of the G protein binds ____ in order to become activated. What happens to the subunit after the protein is activated?
Alpha
GTP
Alpha subunit dissociates and interacts with effector
In terms of number of subunits necessary to make a functional receptor, how does a ligand-gated receptor differ from a G protein-coupled receptor?
Ligand-gated receptor needs multiple subunits to be functional, whereas a G protein-coupled receptor needs only 1
What are the 3 types of trimeric G proteins?
Gs
Gi
Gq
Each type of G protein-coupled receptor binds to how many types of trimeric G protein?
1
For a given ligand, can there be multiple types of G protein-coupled receptors (each one binding 1 type of trimeric G protein)?
Yes
What 2 types of trimeric G proteins work on adenylyl cyclase? Adenylyl cyclase turns ___ into ____, a secondary messenger which activates _____.
Gs Gi ATP cAMP Protein kinase A
Gs _____ adenylyl cyclase, while Gi ______ it.
Stimulates
Inhibits
What type of trimeric G protein works on phospholipase C, and in what manner? Phospholipase C turns ____ into ____ and ____.
Gq
PIP2
DAG
IP3
After phospholipase C turns PIP2 into DAG and IP3, DAG activates ______, while IP3 uses the ion _____ to activate ______ and ____.
Protein kinase C
Ca+2
Protein kinase C
Calcium calmodulin kinase (CaMK)
In a designer receptor exclusively activated by designer drugs (DREADD), the G protein-coupled receptor is ____ so that it no longer binds the ____ ligand. It only binds the artificial ligand ____. Adding the artificial ligand enables ____ of the G protein-coupled receptor.
Mutated
Endogenous
Clozapine-N-oxide (CNO)
Activation
4 mechanisms used to stop neurotransmitter signaling
Diffusion
Enzymatic degradation
Presynaptic reuptake
Glial uptake
Acetylcholine is synthesized where by what? What 2 molecules are used to synthesize it?
Axon terminal
Choline acetyltransferase
Acetyl CoA, choline
The 2 receptors for acetylcholine are the _____ acetylcholine receptor and the ____ acetylcholine receptor. Which is a ligand gated ion channel and which is a G protein-coupled receptor?
Nicotinic
Muscarinic
nAchR is ligand-gated ion channel and mAchR is GPCR
What is the name of the acetylcholine vesicular transporter that puts acetylcholine into vesicles? How is acetylcholine removed from the receptor? Can it be taken back up through reuptake?
VAChT (vesicular acetylcholine transporter)
Degradation by acetylcholinesterase
No
What part of the acetylcholine molecule can undergo reuptake/recycling?
Choline
Organophosphates in insecticides and nerve gas inhibit what enzyme associated with what neurotransmitter?
Acetylcholinesterase
Acetylcholine
Is the nicotinic acetylcholine receptor (nAchR) ion selective? What ions does it pass?
No
Na+ and K+
Is the nAchR a heterotetramer or heteropentamer?
Heteropentamer
What are the 2 agonists for the nAchR? Which is endogenous?
Acetylcholine (endogenous)
Nicotine
What is the antagonist for the nAchR?
Mecamylamine
Do endogenous and non-endogenous agonists bind in the same place on a receptor?
Not necessarily
Myasthenia gravis is what type of condition that does what to the number of nAchRs? How is it treated?
Autoimmune
Reduces
Treated with acetylcholinesterase inhibitors
What are the 2 agonists for the mAchR? Which one is endogneous?
Acetylcholine (endogenous)
Muscarine (mushroom toxin)
What are the 2 antagonists for the mAchR?
Atropine
Scopolamine
Acetylcholine released by the vagus nerve binds to what subunit of the mAchR on the heart to cause slowing down of contraction? What trimeric G protein does that subunit act upon to cause this effect?
M2
Gi (inhibitory effects)
The most abundant excitatory neurotransmitter is _____.
Glutamate
What does glutamatergic mean in respect to a neuron?
It synthesizes glutamate
Can glutamate cross the blood brain barrier? What are its 2 sources of synthesis?
No
Glutamine from glia
2-oxoglutarate from TCA cycle
Is glutamate degraded, or taken back up?
Taken back up
What molecule loads glutamate into vesicles?
VGLUT
In the glutamate-glutamine cycle, (glutamate/glutamine) is made in the glia, transported out by _____, taken into the neuron by _____, made into (glutamate/glutamine) by ____, pumped into vesicles by ____, released into the synaptic cleft, then taken back into glia by _____, where it is turned into glutamine and the cycle starts over.
Glutamine SN1 SAT2 Glutamate Glutaminase VGLUT EAATs
What are the 3 ligand-gated glutamate receptors?
AMPA
NMDA
Kainate
Are the ligand-gated glutamate receptors ion-specific? What ions do they always pass, and which do they sometimes pass?
No
K+, Na+, maybe Ca+2
Are the ligand-gated glutamate receptors heterotetramers or heteropentamers?
Heterotetramers
What 2 ligand-gated glutamate receptors can also pass Ca+2? For which one is the permeability dependent on its subunits?
AMPA and NMDA
AMPA
The NMDA receptor binds what ion at (depolarized/hyperpolarized) potentials?
Mg+2
Hyperpolarized