Ionotropic And Metabotropic Receptors

Question 0

What are metabotropic receptors ?

Answer 0

Coupled to intracellular proteins which transduce the signal to the cell interior
7 transmembrane domains
Single subunit
Effects are longer lasting as they activate 2nd messenger systems

Question 1

What are ionotropic receptors ?

Answer 1

Ligand gated ion channels

Form an ion channel that’s allows the passage of ions which either depolarises or hyperpolarises the cell

Question 2

What is current ?

Answer 2

Measure ion flow

If the flow is inwards then it produces a downward deflection and if it is outward it produces an outward deflection

Question 3

If you get an inward positive current what happens to the postsynaptic potential ?

Answer 3

Excitatory potential which becomes more positive creating a upward deflection

Question 4

What is temporal summation ?

Answer 4

Activating the same synapse with EPSPs in quick succession - combining of EPSPs helps to produce an action potential

Question 5

What is spatial summation ?

Answer 5

This is when a neurone is activated by more than one PSP

Question 6

What is another name for ionotropic acetylcholine receptors ?

Answer 6

Nicotinic acetylcholine receptors because nicotine is an agonist to them

Question 7

What is the general structure and function of nicotinic acetylcholine receptors ?

Answer 7

5 subunits- 2-alpha, beta, gamma and delta
- has to have 2 alpha subunits to bind the 2 acetylcholine molecules
- each subunit has 4 transmembrane domains
- 1 of these domains always faces inwards and it is the amino acid helix of this which determines which ions can pass through
Form a complex with a pore that’s closed at rest
Binding of acetylcholine causes pore to open for <1ms to allow ions through - sodium and potassium

Question 8

Which domain of each subunit in nicotinic acetylcholine receptor faces into the channel ?

Answer 8

Domain 2 - the negatively charged amino acids form the selectively filter

Question 9

What happens to nAChR when the concentration of acetylcholine increases ?

Answer 9

Increases the number of times the channels open

Increases the length of time the channels are open

Question 10

What are the subunits for nAChR in muscle ?

Answer 10

2 alpha, beta, delta, gamma or epsilon - gamma or epsilon is dependent upon the stage of development
Binds alpha- bungarotoxin

Question 11

What subunits for nAChR are present in the brain ?

Answer 11

Either 3 alpha and 2 beta or 5 alpha

Mostly doesn’t bind alpha- bungarotoxin

Question 12

What effect does changing the subunits of an ionotropic receptor do ?

Answer 12

It alters the properties of the channels

Question 13

What are the ionotropic receptors for glutamate ?

Answer 13

AMPA
Kainate
NMDA
Each of these receptors have a variety of subunits to alter the properties

Question 14

What are NMDA receptors important for ?

Answer 14

Learning and memory

Question 15

What are AMPA receptors important for ?

Answer 15

Most important for glutamate excitation

When lots of synaptic activity occurs it is these receptors which activate he NMDA receptors

Question 16

What are kainate receptors important for ?

Answer 16

They seem to have an involvement in epilepsy

Question 17

How many subunits for glutamatergic receptors have ?

Answer 17

4 they are tetramers

Question 18

What are the types of AMPA receptors ?

Answer 18

GluR1 + GluR2 which is the most common type, allowing only sodium and potassium ions through
GluR1 + GluR1 which also allows calcium through
- these are unregulated when there is lots of synaptic activity and the ability to let calcium through means there is a larger depolarisation and the response lasts longer because it can act as a second messenger

Question 19

What is the structure of an NMDA receptor like ?

Answer 19

2 NR1 subunits - binds glycine
2 NR2 subunits - bind glutamate
Allows sodium potassium and calcium ions through
Rest it’s blocked by magnesium ion preventing the passage of any ions

Question 20

What can ions flow through NMDA receptors ?

Answer 20

Only if there has been sufficient depolarisation by AMPA receptors to inhibit the driving force of the magnesium ion so that it leaves the channel
If another action potential occurs then it will be open to allow the passage of ions
Enable flow at high frequencies

Question 21

What is an example of an antagonist for AMPA/kainate receptors ?

Answer 21

NBQX

Question 22

What is an example of an antagonist for NMDA receptors ?

Answer 22

APV

Question 23

What are GABAa receptors like ?

Answer 23

Ionotropic
Allow chloride through
Causes hyperpolarisation
Have many modulatory binding sites which alter the effects of GABA binding

Question 24

Which acetylcholine receptors are more prominent in the brain ?

Answer 24

Metabotropic

Question 25

What are the metabotropic acetylcholine receptors like ?

Answer 25

5 types of receptors
1,3 and 5 are coupled to PLC
2 and 4 are coupled to adenyl Cyclase

Question 26

What are the metabotropic glutamate receptors like ?

Answer 26

8 different ones
Class 1 = 1 and 5 - coupled to PLC
Class 2 = 2 and 3 - decrease cAMP
Class 3 = 4, 5, 6, 7 and 8 - autoreceptors