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Flashcards in Amino Acid Transmitters Deck (26):
1

list the main three amino acid transmitters and the CNS and state whether they are inhibitory or excitatory

1) glutamate - excitatory
2) GABA - inhibitory
3) glycine - inhibitory

2

through which two types of receptors do glutamate and gaba regulate their effects

ion channels (ionotropic) and g protein coupled receptors (metabotropic)

3

where is glutamate synthesised? what are the two mechanisms of synthesis

the brain

1) synthesised from glutamine (from astrocytes) to glutamate by glutaminase

2) glucose metabolism

4

how is glutamate stored?

stored in synaptic vesicles.

H+ conc higher in vesicle than in cytoplasm. outflow of H+ allows transport of glutamate into vesicle

5

what is the mechanism of synaptic release of glutamate

the same as for ACh

6

how is glutamate mainly removed from the synaptic cleft

glutamate transporters on astrocytes.

1) co-transport of (2/3 Na)/H and glutamate

2) exchanging K+ for glutamate

7

name 3 ionotropic glutamate receptors

NMDA, AMPA, Kainate

8

how many polypeptide subunits make up one ionotropic glutamate receptor

4, they are clustered together to form a cylinder with a pore

9

where is the binding site on the glutamate ionotropic receptors

outside, near the N terminus

10

what ions are ampa receptors permeable to

Na and K

11

what ions are NMDA receptors permeable to

Na, K and Ca

12

what ions are kainate receptors permeable to

Na

13

binding of glutamate to AMPA and NMDA receptors causes what type of post synaptic potential

Excitatory post synaptic potential (they depolarise the cell)

14

which other amino acid needs to bind to NMDA receptors for them to function

glycine

15

how many types of metabotropic glutamate receptors are there and how many groups are there

8, grouped in 3 groups

16

where are metabotropic glutamate channels found on neurons

presynaptic and postsynaptic terminals

17

what happens to a g protein once glutamate has bound a metabotropic receptor

gdp is exchanged for gtp on alpha unit.

alpha unit dissociates from beta/gamma heteromer

activates intracellular proteins

18

what intracellular effects are observed when glutamate binds to type I metabotropic receptors

activated alpha subunit causes activation of phospholipase C, creates IP3/DAG

IP3 causes calcium release, DAG activates Protein Kinase C which phosphorylates other proteins

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beta/gamma heteromer binds ion channels and modifies function

19

what intracellular effects does the binding of glutamate on type II and type III mReceptors have

activates g protein G alpha(i) which inhibits production of cAMP

modifies ion channels

20

what are the effects of glutamate binding on presynaptic metabotropic channels

causes beta/gamma heteromer to block voltage gated calcium channels - leads to less excitability

21

what are the effects of glutamate binding on postsynaptic metabotropic receptors

usually opens K+ channels leading to hyperpolarisation and less excitability

22

what is the precursor and enzyme needed for GABA synthesis

glutamate and glutamic acid decarboxylase

23

GABA is broken down by what enzyme

GABA transaminase

24

how is GABA packed into vesicles

H+ ions move out of the vesicle and simultaneously GABA moves in

25

how is GABA removed from synaptic cleft

1) taken up into astrocytes through a co-transporter protein which brings Na and GABA into cell (degraded by GABA transaminase)

2) into postsynaptic neurons (degraded by GABA transaminase)

3) taken up into presynaptic neurons and recycled

26

what kind of receptors does GABA act on

postsynpatic ionotropic

pre/postsynaptic metabotropic