Ligand Gated Ion Channels

Question 1

T/F: Ligand gated ion channels cannot initiate depolarization.

Answer 1

False

Question 2

T/F: Ligand gated ion channels can have Excitatory Postsynaptic Potential (EPSP) or Inhibitory Postsynaptic Potential (IPSP)

Answer 2

True

Question 3

Cholinergic Neurotransmitters

Answer 3

transmit Acetylcholine

Question 4

Purine Neurotransmitters

Answer 4

transmit ATP

Question 5

Biogenic Amine Neurotransmitters

Answer 5

transmit serotonin

Question 6

Amino Acid Neurotransmitters

Answer 6

transmit Glutamate

transmit Glycine, GABA

Question 7

Cationic channels affect EPSP or IPSP?

Answer 7

EPSP

Question 8

Anionic channels affect EPSP or IPSP?

Answer 8

IPSP

Question 9

Four examples of Cationic channels and what they transmit

Answer 9

• Cholinergic = acetylcholine
• purines = ATP
• biogenic amines = serotonin
• amino acids = glutamate

Question 10

Example of anionic channels and what they transmit

Answer 10

amino acids = glycine, GABA

Question 11

Purine Receptor Subunit

Answer 11

• P2X receptors
• nonselective cation channels
• cytosolic N & C termini w/ 1 extracellular loop (loop thought to contain ligand binding spot)
• widely distributed in CNS, PNS, and neuroglia
• may have role in neuropathic pain

Question 12

Acetylcholine (nicotinic), GABAa, and Glycine Receptors

Answer 12

• 4 membrane spanning domains per subunit
• 5 subunits make 1 channel
• extracellular N & C termini

Question 13

Subunits of nAch Receptors

Answer 13

• 2 alpha
• beta
• gamma
• delta

Question 14

Subunits of GABAa Receptors

Answer 14

• 2 alpha
• 2 beta
• gamma

Question 15

Subunits of Gly Receptors

Answer 15

• 3 alpha

- 2 beta

Question 16

What is the primary inhibitory neurotransmitter in the brain and spinal cord?

Answer 16

GABA

Question 17

What is the inhibitory neurotransmitter in the brain and spinal cord that affects antagonistic muscles?

Answer 17

Glycine

Question 18

Glutamate Receptor subunits

Answer 18

• 3 transmembrane segments
• a predicted ‘P’ loop
• 4 or 5 subunits per channel
• All receptor types permeant to Na+ and K+

Question 19

Nicotinic Acetylcholine Receptor shape

Answer 19

heteropentamer

possibilities of:

• alpha 1-9
• beta 1-4
• gamma
• delta
• epsilon

Question 20

Subunits of an adult muscle nicotinic acetylcholine receptor

Answer 20

• 2 alpha
• beta 1
• gamma
• delta

Question 21

Subunits of a neonatal muscle nicotinic acetylcholine receptor

Answer 21

• 2 alpha
• beta 1
• gamma
• epsilon

Question 22

Subunits of a nerve nicotinic acetylcholine receptor

Answer 22

• 2 alpha

- 3 beta

Question 23

Agonists of nAch Receptors

Answer 23

• nicotine
• carbamylcholine
• succinylcholine
• acetylcholine
• lemamisole
• pyrantel target helminth homolog

Question 24

Antagonists of nAch Receptors

Answer 24

• trimethaphan
• alpha Bungarotoxin
• curare

Question 25

What is responsible for binding to acetylcholine in nAch Receptors?

Answer 25

alpha subunits

Question 26

Why is alpha Bungarotoxin considered functionally irreversible?

Answer 26

takes 20 minutes to release from binding site not "real time" for physiological purposes

Question 27

How many subunits are there per receptor for nAchR, GlyR, HT3R, and GABAa receptors?

Answer 27

5 subunits

Question 28

Extracellular Subunit Topology

Answer 28

- Both N and C terminus - consensus sites for glycosylation - 2 cystine residues separated by 13 aa, that form a disulfide bond - responsible for ligand binding

Question 29

Transmembrane Subunit Topology

Answer 29

-4 segments (M1,M2,M3,M4)

Question 30

In the transmembrane subunits, what is responsible for ion selectivity?

Answer 30

M2 M2 is contributed by each of the subunits forms aqeous pore/ ion channel.

Question 31

Intracellular Subunit Topology

Answer 31

- responsible for intracellular processing, targeting, and anchoring - natural mutations have occurred here and disease have been assoc. with these mutations

Question 32

Do Glutamate and Purinergic receptors have the same topology as nAchR, GlyR, HT3R, and GABAa Receptors?

Answer 32

They do NOT share the same topology

Question 33

How many subunits are there in serotonin HT3 Receptors?

Answer 33

5 - It's a heteropentamer | A, B, C, D, and E exist

Question 34

Agonist of serotonin HT3 Receptor

Answer 34

2-methyl serotonin

Question 35

Antagonists of serotonin HT3 receptor

Answer 35

- Dolasetron - Ondasetron - Granisetron - Palonosetron - Alosetron (withdrawn)

Question 36

nAchR, Receptor targeting, and anchoring | neuromuscular junction [5 steps]

Answer 36

1. Post-synaptic cell synthesizes rapsyn 2. Rapsyn interacts with intracellular domain of nAchR 3. At same time, nerves secrete agrin 4. Agrin interacts with dystroglycan 5. Rapsyn interacts with beta dystroglycan and with cytoskeleton

Question 37

What does rapsyn do in regards to the neuromuscular junction?

Answer 37

causes clumping of receptors

Question 38

What does agrin do in regards to the neuromuscular junction?

Answer 38

provides targeting cell for clumped receptors

Question 39

T/F: Ligand-gated channels respond to chemical messenegers

Answer 39

True

Question 40

What accounts for localization, activity, conductance, and pharmacology in many ligand-gated channels?

Answer 40

common structural motif

Question 41

Acetylcholine- and serotonin-gated channels are _______ in nature.

Answer 41

excitatory | ie - strongly depolarizing

Question 42

T/F: Ligand-gated channels provide examples of cooperativity and competitive and noncompetitive inhibition.

Answer 42

True