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Psychopharmacology > Chapter 3: Ion channels > Flashcards

Chapter 3: Ion channels Flashcards

1
Q

what ions do the most important ion channels regulate

A

calcium
sodium
chloride
potassium

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2
Q

what are ion channels made of

A

subunits of amino acids assembled around an ion channel

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3
Q

what 2 things regulate the sensativity of channel opening

A

neurotransmitters
allosteric modulators

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4
Q

structure of pentameric ionotropic receptors

A

5 subunits of 4 transmembrane regions

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5
Q

where are the receptor sites on each subunit

A

some are inside the channel and some are allosteric

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6
Q

Types of pentameric ionotropic receptors

A

GABAa receptors
Nicotinic cholinergic receptors
serotonin 5HT3 receptors
certain glycine receptors

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7
Q

neurotransmitters that act directly on pentameric ionotropic receptors

A

acetylcholine (nicotinic)
GABA (GABAa)
glycine (strychnine-sensative)
serotonin (5HT3)

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8
Q

natural neurotransmitters v. drugs on pentameric ionotropic receptors

A

neurotransmitters bind to every subtype and drugs may bind selectively to 1 or more subtypes

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9
Q

structure of tetrameric ionotropic receptors

A

4 subunits that contain 3 transmembrane regions and 1 entrant loop

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10
Q

where are the 4 re-entrant loops on tetrameric ionotropic receptors

A

they line the ion channel

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11
Q

types of tetrameric ionotropic receptors are

A

Glutamate receptors:
AMPA
Kainate
NMDA

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12
Q

action of full agonists on ionotropic receptors

A

open ion channel to max frequency for max downstream signal transduction

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13
Q

what increases opening of ion channel greater than full agonist

A

presence of a PAM

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14
Q

action of antagonist on ionotropic receptors

A

stabilizes receptor in its resting state (constitutive activity) despite the presence or absence of an agonist

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15
Q

what do antagonists reverse

A

full agonist
partial agonist
inverse agonist

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16
Q

action of partial agonist on ionotropic receptors

A

opens channel greater than constitutive activity but not as great as full agonist depending on how close it is to the full agonist/antagonist

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17
Q

action of an inverse agonist on ionotropic receptors

A

closes channel completely (less action than constitutive activity)

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18
Q

can inverse agonist be distinguished clinically from an antagonist

A

not clear

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19
Q

what are the different states of ionotropic receptors

A

desensitization and inactivation

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20
Q

what is desentiziation of an ionotropic receptor and what causes it

A

when the ion channel quits responding to the agonist over time due to over or prolonged stimulation.
quickly reversible

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21
Q

what is inactivation of an ionotropic receptor and what causes it

A

same as desensitization, however, it is one step past so it takes several hours after agonist is gone before it returns to its resting state and can again be stimulated by the agonist

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22
Q

what is an allosteric modulator

A

ligands that bind to sites other than where the neurotransmitters bind

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23
Q

what is a PAM and what does it do

A

positive allosteric modulator
when it binds to its allosteric site when the agonist is bound it increases the opening more than the full agonist alone

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24
Q

what is a NAM and what does it do

A

negative allosteric modulator
when it binds to its allosteric site while the neurotransmitter is bound it blocks or decreases the action of the neurotransmitter (agonist)

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25
Q

example of PAM

A

benzodiazepines
boost the action of GABA at chloride ion channels

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26
Q

example of NAM

A

NAM for NMDA:
phencyclidine
ketamine

27
Q

when do allosteric sites have PAM action

A

when the ligand is a full agonist

28
Q

when do allosteric sites have NAM action

A

when the ligand is an inverse agonist

29
Q

which neurotransmitters work on pentameric ionotropic receptors

A

acetylcholine
GABA
serotonin

30
Q

which neurotransmitters work on tetrameric ionotropic receptors

A

glutamate

31
Q

examples of drug classes that act on GABA pentameric ionotropic receptors

A

benzodiazepines
Z drugs/hypnotics (zolpidem, zaleplon, zopiclone, eszopiclone)
neuroactive steroids

32
Q

examples of drugs that act on serotonin pentameric ionotropic receptors

A

mirtazepine
vortioxetine
anti-emetics

33
Q

example of drugs that work on glutamate tetrameric ionotropic receptors

A

PCP
ketamine
dextromethorphan
dextromethadone

34
Q

what regulates opening of voltage-sensitive ion channels

A

the charge/voltage across the membrane

35
Q

first phase of opening voltage-sensitive ion channel

A

voltage-sensitive sodium channels open and sodium rushes downhill into the negatively charged, sodium-deficient neuron

36
Q

second phase of opening a voltage-sensitive ion channel

A

influx of sodium changes the voltage of the neuron which triggers the opening of voltage-sensitive calcium channels and calcium rushes in

37
Q

third phase of opening a voltage-sensitive ion channel

A

once action potential is gone, potassium enters neuron and sodium is pumped out which restore electrical milieu back to baseline

38
Q

what makes up the “pore” of VSSCs

A

when 4 amino acid subunits with sodium ionic filters come together to form the hole in the middle

39
Q

what makes up the “pore” of VSCCs

A

when 4 amino acid subunits with calcium ionic filters come together to form the hole

40
Q

what is the pore called on VSSCs

A

subunit a

41
Q

what is the pore called on VSCCs

A

subunit a1

42
Q

which transmembrane proteins flank subunit a (pore) of VSSCs and what do they do

A

B units and their function is not clearly established

43
Q

how many transmembrane regions are on the amino acid subunits that make up VSSCs and VSCCs

A

6

44
Q

which transmembrane segment detects the difference in charge across the membrane of voltage-sensitive ion channel subunits and why is that important

A

transmembrane segment 4
alerts the rest of the protein when it senses a change in charge which triggers conformational changes that open/close the channel

45
Q

where is the extracelluar loop on voltage-sensitive ion channel subunits and why is it important

A

between transmembrane segments 5 and 6
functions as a filter to either allow sodium (VSSC) or calcium (VSCC) to enter

46
Q

how are the subunits of voltage-sensitive ion channels connected

A

by connector loops

47
Q

what is the significance of the connector loop between transmembrane units 3 and 4

A

act as a plug to close the channel

48
Q

what are the three states of voltage-sensitive ion channels

A

open and active
inactivated
closed and inactivated

49
Q

open and active state of voltage-sensitive ion channels

A

allow max flow of ions across the membrane

50
Q

inactivated state of voltage-sensitive ion channels

A

loop goes into pore to stop the flow of ions immediately (before channel is even closed)

51
Q

closed and inactivated state of voltage-sensitive ion channels

A

when there are conformational changes in the ion channels shape that closes it

52
Q

what is the pore called on VSCCs

A

subunit a1

53
Q

extracellular proteins that flank subunit a1

A

y (spans the membrane)
B (cytoplasmic units)
a2ẟ

54
Q

pregabalin and gabapentin target which extracellular protein of VSCCs

A

a2ẟ

55
Q

types of VSCCs

A

N or P/Q channels
L channels
R and T channels

56
Q

N or P/Q channels of VSCCs

A

presynaptic regulators of neurotransmitter release

57
Q

what is the “snare” in VSCCs

A

the amino acid loop that connects the 2nd and 3rd subunits work as a “snare” to hook to the synaptic vesicle to regulate the release of the neurotransmitter into the synapse during neurotransmission

58
Q

how does the molecular “snare” work in N or P/Q voltage-sensitive ion channels

A

If a drug interferes with calcium entering the cell then the vesicle stays tethered to the channel and neurotransmission is prevented. When calcium enters the cell, the snare docks with the vesicles and moves it to the synapse so the neurotransmitter can spill into it.

58
Q

how does the molecular “snare” work in N or P/Q voltage-sensitive ion channels

A

If a drug interferes with calcium entering the cell then the vesicle stays tethered to the channel and neurotransmission is prevented. When calcium enters the cell, the snare docks with the vesicles and moves it to the synapse so the neurotransmitter can spill into it.

59
Q

what is another term for the work of the snare in N or P/Q voltage-sensitive ion channels

A

excitation-coupling

60
Q

Where do L channel VSCC reside

A

in the CNS but also on vascular smooth muscle

61
Q

R and T channel voltage-sensitive ion receptors

A

exact roles being clarified
some anticonvulsants and psychotropic drugs interact here

62
Q

discuss ion channels and neurotransmission

A

neuron receives info from previous neuron and encodes it into an action potential.
the impulse is sent down the axon via VSSCs.
when the impulse reaches the axon terminal it meets VSCCs in the presynaptic membrane.
when the voltmeter in the VSCC detects the impulse they open to allow calcium into the neuron. Then neurotransmitter is released into the synapse

Psychopharmacology (14 decks)

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