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Neurobiology > Ionotropic/metabotropic Receptors > Flashcards

Ionotropic/metabotropic Receptors Flashcards

0
Q

Inward current produces a _____ deflection?

A

Downward

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1
Q

Current is a measure of ion flow in what direction?

A

Direction of POSTITIVE ion

Opposite direction to -ve ion

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2
Q

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

A

Mirror image

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3
Q

IONOTROPIC receptors consist of how many subunits?

A

4 or 5

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4
Q

Which subunits of the nAChR have the ACh binding sites?

A

2 alpha subunits

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5
Q

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

A

TM2

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6
Q

Each TM2 has what that forms the selectivity filter?

This makes nAChR selective to____?

A

Negatively charged AAs

cations

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7
Q

How do muscle and brain nAChRs differ?

A

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

2) Muscle nAChR binds alpha BUNGAROTOXIN, brain does not

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8
Q

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

A

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

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9
Q

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

A

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

AMPA (GluR1-4)

Kainate (GluR5-7, KA1, KA2)

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10
Q

How many subunits do ionotropic glutamate receptors have?

A

4

Tetramers

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11
Q

What is the major receptor for excitatory transmission?

A

AMPA

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12
Q

What is the structure of an AMPA receptor?

What are the two most common conformations?

A

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)

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13
Q

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

A

Lots of synaptic activity

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14
Q

What is the subunit composition of an NMDA receptor?

A 
2 x NR1 (glycine)
2x NR2 (glutamate)
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15
Q

What is the role of glycine in NMDA receptor?

A

Co-agonist

Need both glut and glyc to open channel

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16
Q

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

Why is the channel not open at resting potentials?

A

Na, Ca (and K)

Pore blocked by Mg2+

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17
Q

NMDA receptor is known as a _______ detector?

A

Coincidence

18
Q

Explain why inward current of NMDA receptor is voltage-dependent

A

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
Q

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

A

Long term potentiation

important for learning and memory

20
Q

The function of which receptor is important for synaptic plasticity?

A

NMDA

21
Q

Describe the current through an AMPA and NMDA receptor?

A

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

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

22
Q

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

A

Allosteric modulators

23
Q

What effect do benzodiazepines have on GABAa?

A

Potentiate GABA activity
Agonist
Increase frequency of channel opening

24
Q

What effect do barbiturates have on GABAa?

A

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

25
Q

Steroids have similar effect on GABAa as_____?

A

Barbiturates

26
Q

What effect do picrotoxins have on GABAa?

A

Inhibit channel
Acts on gating process
Decreases time channel open

27
Q

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

A

Barbiturates, steroids, picrotoxin

28
Q

How many subunits form GABAa?

Which subunits have GABA binding sites?

A

5 (pentameric)

B subunits

29
Q

What is the common structure of metabotropic receptors?

What are exceptions to this?

A

Monomeric

Glutamate and GABA receptors = dimers

30
Q

G proteins are _____ proteins?

A

Trimeric

31
Q

Which G protein subunit binds GDP and interacts with GPCR?

A

Alpha

32
Q

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

A

GDP replaced by GTP

a subunit dissociates from By subunits

33
Q

How do G-protons return to inactive state?

A

a subunit hydrolyses GTP to GDP

a re associates with By

34
Q

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

A

Can’t be hydrolysed

Subunits remain active

35
Q

Give 8 metabotropic receptor classes

A

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

36
Q

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

Which receptor subtypes are in each class?

A

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

37
Q

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

And located mostly pre or post synaptic?

A

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

Postsynaptic

38
Q

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

And located mostly pre or post synaptic?

A

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

Presynaptic

39
Q

How are mGluRs modulatory?

A

Modulate neurone and determine future cell response

Make cell more or less likely to fire

40
Q

How specifically are group I mGluRs modulatory ?

A

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
Q

What is the modulatory effect of group II mGluRs?

A

Gi -> inhibit cAMP

Reduce NT release

42
Q

GABAb is a hetrodimer. Which monomer binds GABA?

A

R1

43
Q

Activation of GABAb is inhibitory, how?

A

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

Neurobiology (9 decks)

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