Ionotropic/metabotropic Receptors Flashcards Preview

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Flashcards in Ionotropic/metabotropic Receptors Deck (44):
0

Current is a measure of ion flow in what direction?

Direction of POSTITIVE ion

(Opposite direction to -ve ion)

1

Inward current produces a _____ deflection?

Downward

2

Membrane potential (EPSP/IPSP) is a __________ of the current (EPSC)?

Mirror image

3

IONOTROPIC receptors consist of how many subunits?

4 or 5

4

Which subunits of the nAChR have the ACh binding sites?

2 alpha subunits

5

The transmembrane domains of each subunit are arranged so that which domain forms the pore?

TM2

6

Each TM2 has what that forms the selectivity filter?

This makes nAChR selective to____?

Negatively charged AAs

cations

7

How do muscle and brain nAChRs differ?

1) SUBUNITS: - muscle has 2a, B, d, y or E.
- brain 3a, 2B or 5a

2) Muscle nAChR binds alpha BUNGAROTOXIN, brain does not

8

Other than nACh what other IONOTROPIC receptors are there (7)?

AMPA, NMDA, kainate, 5-HT, purines, GABA, glycine

9

What are the 3 types of IONOTROPIC glutamate receptors and their possible subuints?

NMDA (NMDAR1, NMDAR2a-d, NMDAR3a-b)

AMPA (GluR1-4)

Kainate (GluR5-7, KA1, KA2)

10

How many subunits do ionotropic glutamate receptors have?

4
(Tetramers)

11

What is the major receptor for excitatory transmission?

AMPA

12

What is the structure of an AMPA receptor?

What are the two most common conformations?

Dimer or dimers

GluR1/GluR2: -most common, allows Na+ to pass. GluR2 controls Ca permeability, prevents Ca entry

GluR1/GluR1: - formed due to activity/insult. Allows passage of Na and Ca => larger depolarization (+ Ca acts as 2nd messenger)

13

What stimulates an increase in expression of AMPA receptors (esp GluR1 hetromer) in postsynaptic membrane?

Lots of synaptic activity

14

What is the subunit composition of an NMDA receptor?

2 x NR1 (glycine)
2x NR2 (glutamate)

15

What is the role of glycine in NMDA receptor?

Co-agonist

(Need both glut and glyc to open channel)

16

What ions does the NMDA receptor allow to pass when open?

Why is the channel not open at resting potentials?

Na, Ca (and K)

Pore blocked by Mg2+

17

NMDA receptor is known as a _______ detector?

Coincidence

18

Explain why inward current of NMDA receptor is voltage-dependent

Resting potentials- pore blocked

Upon depolarization (due to AMPA activation) Mg2+ is forced out of pore, allowing influx of Na/Ca

NMDA activity needs high-frequency stimuli

19

What is the Ca2+ entering NMDA (acting as 2nd messenger) important for?

Long term potentiation

(important for learning and memory)

20

The function of which receptor is important for synaptic plasticity?

NMDA

21

Describe the current through an AMPA and NMDA receptor?

AMPA: rapid rise in current but v transient (dissipates quickly)

NMDA: slower activation, current doesn't reach max, but sustained/lasts longer

22

GABAa receptors have binding sites for _______ that change effect of GABA binding on the receptor?

Allosteric modulators

23

What effect do benzodiazepines have on GABAa?

Potentiate GABA activity
Agonist
Increase frequency of channel opening

24

What effect do barbiturates have on GABAa?

Agonist
Increase binding of GABA and benzodiazepines
Increase time channel open (increased Cl- flux)

25

Steroids have similar effect on GABAa as_____?

Barbiturates

26

What effect do picrotoxins have on GABAa?

Inhibit channel
Acts on gating process
Decreases time channel open

27

What allosteric modulator binding sites are located in the pore of GABAa?

Barbiturates, steroids, picrotoxin

28

How many subunits form GABAa?

Which subunits have GABA binding sites?

5 (pentameric)

B subunits

29

What is the common structure of metabotropic receptors?

What are exceptions to this?

Monomeric

Glutamate and GABA receptors = dimers

30

G proteins are _____ proteins?

Trimeric

31

Which G protein subunit binds GDP and interacts with GPCR?

Alpha

32

What happens upon activation of a G-protein when it interacts with GPCR?

GDP replaced by GTP

a subunit dissociates from By subunits

33

How do G-protons return to inactive state?

a subunit hydrolyses GTP to GDP

a re associates with By

34

What is special about GTP-y-s which binds G proteins?

Can't be hydrolysed
Subunits remain active

35

Give 8 metabotropic receptor classes

Glutamate, GABAb, histamine, 5-HT, purines, dopamine, NA/Ad, muscarinic

36

How many classes/groups of mGluRs (mGluR1-7) are there?

Which receptor subtypes are in each class?

3
Group I: mGluR1 + mGluR5
Group II: mGluR2 + mGluR3
Group III: mGlurR4,6,7,8

37

Group I mGluRs are coupled to which type of G protein?

And located mostly pre or post synaptic?

Gq (PLC -> DAG + IP3 -> PKC + Ca -> increased protein phos + activated Ca binding proteins)

Postsynaptic

38

Group II mGluRs are coupled to which type of G protein?

And located mostly pre or post synaptic?

Gi (inhibits ad cyc and cAMP -> decreased pka an decreased protein phos)

Presynaptic

39

How are mGluRs modulatory?

Modulate neurone and determine future cell response
Make cell more or less likely to fire

40

How specifically are group I mGluRs modulatory ?

Gq -> PKC
PKC modulates AMPA receptors, internalises receptors so glut can't bind
Can't contribute to future EPSPs, less likely to be excited

41

What is the modulatory effect of group II mGluRs?

Gi -> inhibit cAMP

Reduce NT release

42

GABAb is a hetrodimer. Which monomer binds GABA?

R1

43

Activation of GABAb is inhibitory, how?

Coupled to Gi
Decreased protein phosphorylation
Increased k+ channel activity (hyper polarises cell)
Inhibits Ca channels (less Ca influx = less NT release)