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Flashcards in nAChR Deck (50)
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1
Q

What does the transmitter do?

A

It binds to the channel resulting in the channel becoming opened. Ions flow selectively through the channel.

2
Q

How many transmitter binding sites are there per receptors?

A

Usually more than one. Average 2.

3
Q

What is the typical rate of ions to flow through a channel?

A

10 million ions per second.

4
Q

What happens when nicotinic receptors are activated?

A

Leading to opening of the associated cation-conducting ion channel.

5
Q

How many subunits are the nicotinic receptors made up of?

A

5 subunits.

6
Q

What technique is used to observe the activity of single receptors?

A

Use of the patch-clamp technique.

7
Q

Describe the “patch-clamp technique”?

A

Fire-polish the tip of the electrode and connect it to the cell (using a syringe to suck).

8
Q

Name the 4 different confirmations of the patch-clamp technique?

A

Cell attached. Whole-cell Inside-out Outside-out

9
Q

What are the 2 advantages of using cell-attached patch?

A
  1. Intracellular milieu is maintained. 2. Control of the extracellular solution.
10
Q

What are the 3 disadvantages of using cell-attached patch?

A
  1. Investigating different conc. of drugs. 2. Agonist always present. 3. No control of the intracellular content.
11
Q

What are the 3 advantages of using whole-cell voltage clamp?

A
  1. Control of the intracellular and extracellular milieu. 2. Record from a population of receptors. 3. Introduce biochemical modulators intracellularly.
12
Q

What are the 2 disadvantages of using whole-cell voltage clamp?

A
  1. Biochemical “washout” of the intracellular milieu. 2. Resolution- rarely observe single receptors.
13
Q

What are the 2 advantages of using outside-out patch clamp?

A
  1. Control of the intracellular and extracellular milieu. 2. Can change extracellular drug conc.
14
Q

What are the 2 disadvantages of using outside-out patch clamp?

A
  1. Biochemical “washout” of the intracellular milieu. 2. Cannot change intracellular messengers.
15
Q

What are the 2 advantages of using inside-out patch clamp?

A
  1. Control of the intracellular & extracellular milieu. 2, Can introduce biochemical modulators.
16
Q

What is the 1 disadvantage of using inside-out patch?

A

Cannot change the concentration of agonist.

17
Q

Is the nAChR selective or non-selective for cation channels?

A

Non-selective

18
Q

The different confirmations of the nAChR?

A

Mainly it usually requires two agonist to bind before it opens. However, there is a chance that it will open when only one agonist is bound. Thus had a numerous different states. Bound closed (1A). Bound open (1A). Bound closed (2A) and bound open (2A)

19
Q

What is the difference when the nAChR is opened by one agonist or two?

A

When one opens it it is only mono-liganded and is brief in its opening. When two opens it: it is bi-liganded therefore it is prolonged opened with brief closures.

20
Q

Name two subtypes of nAChR?

A

Ganglionic and skeletal muscle.

21
Q

What family is the nAChR a member of?

A

The cys-loop transmitter-gated ion channel family

22
Q

What other receptors are the nAChR closely related to?

A

GABAA, glycine and 5HT3 receptors.

23
Q

Name the 5 subunits that make up the nAChR?

A

alpha. Beta. Delta. Alpha. Epilson Usually: many different subtypes depending on function of the receptor

24
Q

What part of the nAChR does the ACh bind?

A

ACh binds to the part between delta& alpha subunit and between alpha&epilson.

25
Q

What part of the subunit does the ACh bind?

A

At the subunit interfaces.

26
Q

Name the 3 transmitter-gated ion channel family of receptors?

A

Cys-loop receptor Glutamate receptor family. P2X receptor family.

27
Q

What are the characteristics of the Cys-loop receptor superfamily?

A

Pentamer. NH3 and COO on the outside. eg. nAChR, GABAA and glycine.

28
Q

What are the characteristics of the glutamate receptor family?

A

Tetramer. 4 subunits-> 2nd not fully spanning. eg. NMDA and AMPA receptor.

29
Q

What are the characteristics of the P2X receptor family?

A

Trimer. eg. P2X receptor.

30
Q

Whats a characteristic of the nACh receptor that is related to its function?

A

It has a large loop located between TM3 and TM4 located at the intracellular portion of the receptor.

31
Q

Define the term “PAMs”?

A

Positive allosteric modulators.

32
Q

Describe two-electrode voltage clamp?

A

Oocyte clamped at -60mV. Current passing at one end of the membrane and voltage sensing at the other end. Record what happen on application of neurotransmitter.

33
Q

What relates subunit protein to function?

A

alpha7-5HT3A

34
Q

What is the agonist of the alpha 7 receptor?

A

ACh.

35
Q

What is the agonist of the 5-HT3A receptor?

A

5-HT

36
Q

What is the agonist of the alpha7/5HT3A receptor?

A

ACh

37
Q

What does alpha-bungarotoxin do to the alpha 7 receptor?

A

Blocks the agonist from binding.

38
Q

What does the alpha-bungarotoxin do to the 5-HT3A receptor?

A

No effect.

39
Q

What does the alpha-bungarotoxin do the alpha7/5HT3A receptor?

A

Blocks the agonist from binding

40
Q

What is the conductance of the alpha 7 receptor?

A

Large

41
Q

What is the conductance of the 5-HT3A receptor?

A

Small

42
Q

What is the conductance of the alpha7/5HT3A receptor?

A

Small

43
Q

Where is TM2 amino acid located on the nAChR?

A

On the cation conductance.

44
Q

Name two extracellular influences that can effect cation conductance?

A

Glutamate and aspartate.

45
Q

How is cationic nAChR a7 mutated to anionic?

A

By mutating Glu to Arg of the M2 segment

46
Q

How is anionic a1-GlyR mutated to cationic?

A

By mutating Arg to Glu of the M2 segment

47
Q

Difference in conductance between homomeric and heteromeric 5HT3A receptors?

A

Homomeric has a lower conductance value compared to heteromeric.

48
Q

Why is there a noticeable difference in conductance between homomeric and heteromeric 5HT3A receptors?

A

Changes within the intracellular loop between TM3 and TM4.

49
Q

Where in the 5HT3A receptor is the determinant of conductance?

A

Mapped to 21 AAs in the large intracellular loop between TM3 and TM4.

50
Q

Define the watering can model of ion conductance?

A

Ions were thought to travel straight through a channel while the watering can model suggests that the channel disperses ions in all direction when it passes through.