Amino Acid Transmitters Flashcards Preview

PPCNS > Amino Acid Transmitters > Flashcards

Flashcards in Amino Acid Transmitters Deck (26):

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


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

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


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


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


what is the mechanism of synaptic release of glutamate

the same as for ACh


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


name 3 ionotropic glutamate receptors

NMDA, AMPA, Kainate


how many polypeptide subunits make up one ionotropic glutamate receptor

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


where is the binding site on the glutamate ionotropic receptors

outside, near the N terminus


what ions are ampa receptors permeable to

Na and K


what ions are NMDA receptors permeable to

Na, K and Ca


what ions are kainate receptors permeable to



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

Excitatory post synaptic potential (they depolarise the cell)


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



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

8, grouped in 3 groups


where are metabotropic glutamate channels found on neurons

presynaptic and postsynaptic terminals


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


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


beta/gamma heteromer binds ion channels and modifies function


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


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


what are the effects of glutamate binding on postsynaptic metabotropic receptors

usually opens K+ channels leading to hyperpolarisation and less excitability


what is the precursor and enzyme needed for GABA synthesis

glutamate and glutamic acid decarboxylase


GABA is broken down by what enzyme

GABA transaminase


how is GABA packed into vesicles

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


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


what kind of receptors does GABA act on

postsynpatic ionotropic

pre/postsynaptic metabotropic