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Neuropharmacology > GABA, Glutamate and their receptors > Flashcards

GABA, Glutamate and their receptors Flashcards

0
Q

what are metabotropic receptors ?

A

coupled to G protein - open or close ion channels via intermediaries
slower response
transduce signal to the cell interior - indirectly activate ion channels on the plasma membrane through signalling cascade which involved G proteins

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1
Q

what are ionotropic receptors?

A

ligand gated ion channels
rapid response
depolarise or hyperpolarise the post synaptic cell- depends on receptor type and ionic gradient

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2
Q

what is glutamate ?

A

most abundant excitatory neurotransmitter in the vertebrae nervous system

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3
Q

what is GABA?

A

most abundant inhibitory neurotransmitter in the vertebrate nervous system

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4
Q

when glutamate and is present in the synaptic cleft where does it go to be removed ?

A

enters glial cells or astrocytes or presynaptic terminal

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5
Q

what enzyme converts glutamate to glutamine ?

A

glutamine synthetase

glutamine can be taken from glial cells into neurons

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6
Q

if too much glutamate is present what can it cause ?

A

excitotoxicity
it can be highly toxic

a low concentration of glutamate applied to neurons in culture kills the cells

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7
Q

what was discovered in the 1970s about glutamate ?

A

glutamate given orally produces neurodegeneration in vivo

- this caused considerable alarm because of the widespread use of glutamate as a taste enhancing food additive MSG

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8
Q

what is excitotoxcity associate with ?

A

activation of NMDA receptors

  • results mainly from a sustained rise in intracellular calcium concentration
  • there are mechanism that act normally to protect neurones- calcium transport system
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9
Q

what are the glutamate receptors like ?

A

metabotropic ones - mGluRs 1-8
- slow and modulatory

ionotropic ones

  • AMPA, Kainate and NMDA - receptors are named after the agonists that bind to them with high specificity
  • fast synaptic transmission
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10
Q

what are the subunits of NMDA receptors ?

A

NR1
NR2A, B, C and D
NR3A and B

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11
Q

what are the subunits of AMPA receptors?

A

GluR1
GluR2
GluR3
GluR4

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12
Q

what are the subunits of Kainate receptors ?

A 
GluR5 
GluR6 
GluR7 
KA1
KA2
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13
Q

what are the classes of metabotropic glutamate receptors ?

A 
class1 - mGluR1 and mGluR5 
class2- mGluR2 and mGluR3 
class 3 - mGluR4, mGluR6, mGluR7 and mGluR8
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14
Q

what effects does activation of class 1 glutamate receptors have ?

A

stimulates phospholipase c
PIP2 is cleaved into DAG and IP3

they are activated by trans-ACPD and quisqualate

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15
Q

what happens when class 2 glutamate metabotropic receptors are activated ?

A

inhibit adenylyl cyclase

activated by trans-ACPD and quisqualate

16
Q

what happens when the class 3 glutamate metabotropic receptors are activated ?

A

inhibit adenylyl cyclase
activated by L-AP4 and L-SOP
no effect caused by trans-ACPD and quisqualte so they can be differentiated from the class 2 receptors
act ass autoreceptors

17
Q

what is the obligatory subunit of NMDA receptors ?

A

NR1

if its not present then the channel cannot function

18
Q

what binds to the NR1 subunit of NMDA receptors ?

A

glycine
it doesnt actually activate the channel because it is a co agonist however it causes greater activation when glutamate binds

19
Q

what is PCP and what does it bind to ?

A

angel dust

binds to NMDA receptors

20
Q

what are the rules of assembly of AMPA receptors ?

A
  • homomultimers= 2 or more identical components

- heteromultimers= 2 or more different components

21
Q

what are the rules of assembly of kainate receptors ?

A

GluR 5, 6 and 7 are homomultimers

heteromultimers

22
Q

what are the rules of assembly of NMDA receptors ?

A

heteromultimers
NR1 must partner 1 or more NR2 subunits
assemble as hetero-tetramers of 2 obligatory NR1 subunits and 2 regionally localissed NR2 subunits

23
Q

what are the modulatory sites of NMDA receptors ?

A

glycine binding sites
polyamine antagonist site
Mg 2+ block
channel blocking drugs

24
Q

what drugs target glutamate receptors ?

A

ketamine
PCP
AMPAkines

25
Q

what percentage of synapses does GABA localise to ?

A

30%

26
Q

what drugs are GABAa receptors sensitive and insensitive to and what are the effects of its activation ?

A

sensitive to BICUCULLINE
insensitive to BACLOFEN
activation causes chloride influx to hyperpolarize the cell

27
Q

what drugs are GABAb receptors sensitive and insensitive to and what are the consequences of its activation ?

A

sensitive to BACLOFEN
insensitive to BICUCULLINE
modulates neurotransmitter release via potassium ad calcium channels

28
Q

where is the GABA binding site in GABAa receptors?

A

between the alpha and beta subunits

29
Q

where is the benzodiazepine binding site in the GABAa receptors ?

A

between the alpha and gamma subunits

30
Q

where is the alpha 1 subunit of GABAa receptors present ?

A

widely distributed throughout brain

31
Q

where are the alpha2 subunits of GABAa receptors present ?

A

mainly present in the hippocampus

32
Q

where are alpha 3 subunits of GABAa receptors present ?

A

mostly in the cortex- none in the cerebellum

33
Q

where are the alpha 4 subunits of the GABAa receptors present ?

A

some in the hippocampus

low level expression throughout the brain

34
Q

where are the alpha 5 subunits of the GABAa receptors present ?

A

present in CA1 and CA3 regions in the hippocampus

35
Q

where are the alpha 6 subunits of the GABAa receptors present ?

A

100% in cerebellum - not present anywhere else

36
Q

what effect does GABA subunit composition have ?

A

it determines the intrinsic properties of the channel- affinity, kinetics, conductance, allosteric modulation, probability of channel opening, interaction with modulatory proteins and subcellular distribution

37
Q

what is the typical in vivo subunit composition of GABAa receptors ?

A

2 alpha, 2 beta and one gamma or delta subunit

Neuropharmacology (15 decks)

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