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Basic Pharmacology > 2. Receptors > Flashcards

2. Receptors Flashcards

(60 cards)

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1
Q

Atenolol targets what? For what?

A
  • B2 adrenoreceptors
  • hypertension
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2
Q

Benzodiazepine targets what? For what?

A
  • GABAa receptor (ion channel)
  • anti-anxiety
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3
Q

Penicillin targets what? For what?

A

transpeptidase
- antibiotics

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4
Q

Probenecid targets what? For what?

A
  • organic anion transporter (carrier)
  • prolong penicillin action
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5
Q

What does a drug do at receptor targets?

A
  • agonists activate receptor
  • antagonists block action of agonist
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6
Q

What does a drug do at ion channel targets?

A
  • either block
  • or modulate the open/close of it
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7
Q

A benzodiazepine is given to ..

A

calm patients down

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8
Q

How does benzodiazepine work?

A
  • anxious patients have too much chloride trandsuction
  • benzo binds at an allosteric site near the GABA binding site
  • to enhance effects of GABA
  • when benzo and GABA act together, reduces chloride transduction and hyperpolarizes cell
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9
Q

What do drugs do at enzyme targets?

A

either inhibit or act as false substrate

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10
Q

How do NSAIDs work?

A
  • immune activation, tissue damage etc damage phospholipids in the cell membrane
  • this activates phospholipase A2 to work to produce arachidonic acid
  • this with the work of cyclooxygenase forms prostaglandins (these cause inflammation, pain and fever)
  • NSAIDs stop cyclooxygenase and prevent prostaglandin production
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11
Q

What do drugs do at carrier targets?

A
  • transported in place of endogenous substrate
  • inhibit transport
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12
Q

Define ‘receptor’

A

sensing elements in chemical communication systems that coordinate function of different body cells

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13
Q

Agonists … action of endogenous chemical messengers and antagonists … it

A

mimic
block

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14
Q

Define ‘agonist’

A
  • a ligand (drug, neurotransmitter or hormone)
  • that combines with receptors to elicit cellular response
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15
Q

Example of an agonist

A
  • histamine
  • acts as agonist at H1 receptor in smooth muscle
  • increases local blood flow
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16
Q

Define ‘antagonist’

A

drug which blocks response to agonist

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17
Q

Example of an antagonist

A
  • terfenadine
  • antagonist at H1 receptors in smooth muscle
  • decrease local blood flow
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18
Q

What does receptor sub-types mean?

A
  • receptors within a family occur in different molecular varieties
  • have similar structures but significant differences in pharmacological responses
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19
Q

How to identify receptor sub-types?

A
  • on selectivity of agonists/antagonists (ligand binding assays)
  • by cloning techniques
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20
Q

Give the subtypes of histamine receptor and what their agonist/antagonists are

A
  • H1 ag is histamine, antag is terfendine
  • H2 ag is histamine, antag is cimetidine
  • H3 ag is histamine, antag is thioperamide
  • H4 is same as above
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21
Q

How can receptor subtypes elicit different cellular effects?

A
  • receptor with bound agonist is activated
  • activated receptor has altered physical and chem proporties
  • leads to changes within cell that cause biological response
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22
Q

4 receptor types that respond to drugs

A
  • ligand gated ion channels
  • G-protein coupled receptors
  • enzyme/kinase linked receptors
  • intracellular/nuclear receptors
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23
Q

Difference between ligand gated and voltage gated receptors

A
  • ligand gated are channel linked receptors and require an agonist to open the channel
  • voltage gated are not linked to receptors and require a change in electrical charge across a membrane to open/close
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24
Q

Example of a ligand gated receptor

A
  • nicotinic acetylcholine receptor
  • ACh causes skeletal muscle to contract by opening ligand-gated channels
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25
Example of a voltage-gated receptor
- sodium ion channels in nerve cell membranes - local anaesthetics work to block these
26
Nicotinic ion channel is what structure?
- pentamer of 5 subunits - 2 alpha, a beta, a gamma and a delta
27
Resting vs active state of a nicotinic ion channel
- inside in resting is kinked and ion channel is closed - when ligand or agonist binds to extracellular binding site, change in conformational shape - twists around and opens kink to allow cations to go through
28
Clinical use of ACh antagonists
- in skeletal muscle, ACh acts on nicotinic receptor to cause muscle contraction - nicotinic ACh receptor antagonists are muscle relaxants to allow surgical procedures
29
2 examples of G protein coupled receptors and what drugs work on them
- alpha/beta adrenoreceptors for epinephrine - beta 2 adrenoreceptors for salbutamol
30
G protein coupled receptors are the smallest/largest receptors How are they structured?
- largest - single polypeptide chain with 7 transmembrane helices - 3 subunits (alpha, beta and gamma)
31
G protein coupled receptors are slow/fast
- slower than others - minutes
32
How is specificity of G-protein coupled receptors achieved?
- through molecular variation in alpha subunits - Gs, Gi, Gq and G0
33
What does the Gs protein on G protein coupled receptors do?
- activates adenylyl cyclase - activates calcium ion channels
34
What does the Gi protein on G protein coupled receptors do?
- inhibits adenylyl cyclase - activates potassium ion channels
35
What does the Gq protein on G protein coupled receptors do?
activates phospholipase C
36
What does the Go protein on G protein coupled receptors do?
doesn't have an alpha subunit
37
Explain Gs protein signal transduction
- unoccupied receptor doesn't interact with Gs protein - hormone or neurotransmitter binds to receptor - occupied receptor changes shape and interacts with Gs protein - Gs protein releases GDP and binds to GTP - alpha subunit of Gs protein dissociates and activates adenylyl cyclase - adenylyl cyclase catalyzes formation of cAMP - when hormone is no longer present, receptor reverts to resting state - GTP is hydrolysed to GDP and adenylyl cyclase is deactivated
38
All subunits of adrenoreceptors are activated by ...
adrenaline or noradrenaline
39
Response in a particular cell of adrenoreceptor is dependent on ...
which receptor subtype is expressed
40
What happens to adrenoreceptor alpha 1 when adding adrenaline?
- is the Gq form - activates PLC - get vasoconstriction
41
What happens to adrenoreceptor alpha 2 when adding adrenaline?
- is Gi form - inhibits adenylyl cyclase - auto-inhibition of neurotransmitter release
42
What happens to adrenoreceptor beta 2 when adding adrenaline?
- Gs form - stimulate adenylyl cyclase - bronchodilation
42
What happens to adrenoreceptor beta 1 when adding adrenaline?
- Gs form - stimulates adenylyl cyclase - accelerated heart rate
43
... is a beta 2 receptor agonist
salbutamol
44
... is a beta 1 receptor antagonist
atenolol
45
2 examples of kinase-linked receptors
- insulin receptor for insulin - tyrosine kinase for imatinib
46
Structure of 'kinase-linked receptors'
- large extracellular ligand binding domain connected to intracellular domain by single membrane-spanning helix
47
4 things formed by kinase-linked receptors
- receptor tyrosine kinase i.e insulin - serine/threonine kinase - cytokine - guanylyl cyclase-linked
48
3 steps of kinase-linked receptors
- ligand binding - dimerisation - autophosphorylation
49
How do insulin binding receptors work as kinase-linked receptors?
- insulin binding activates receptor tyrosine kinase activity in intracellular domain of beta subunit of insulin receptor - tyrosine residues of beta subunit are auto-phosphorylated - receptor tyrosine kinase phosphorylates other proteins like insulin receptor substrates - phosphorylated IRS promote activations of other protein kinases and phosphatases, leading to biologic actions of insulin - for example lowered blood glucose levels
50
2 examples of nuclear receptors
- estrogen receptor for estradiol - estrogen receptor for tamoxifen
51
Are nuclear receptors highly expressed?
- about 40 types so no - heavily involved in kinetic reactions of drugs and interacts with gene transcription to increase proteinsynthesis - but effects seen over months, years
52
Nuclear receptors are a family of ... ... receptors
48 soluble
53
2 classes of nuclear receptors
- class 1 (in cytoplasm, forming homodimers, ligands are endocrine - steroids, hormones) - class 2 (in nucleus, form heterodimers, ligands are lipids - fatty acids)
54
Binding to … in nuclear receptors creates … changes
hormone response elements Gene transcription changes - pos or neg
55
Explain nuclear receptor class 1 signal transduction
- unoccupied receptor doesn't provide intracellular signal - lipid soluble drug diffuses across cell membrane - drug binds to receptor and occupied receptor changes shape and activates - activated receptor moves to nucleus - drug-receptor complex binds to chromatin, activating transcription of specific genes - mRNA is translated into specific proteins resulting in specific biologic response
56
Most receptor operated channels have single/multiple binding sites. Explain
- multiple - nACHR - heteromers 2 sites, homomers up to 5 - glycine Rs at least 4 sites - binding at one site alters binding at another (pos or neg)
57
3 types of allosteric sites
- positive - negative - allosteric antagonists
58
4 types of orthosteric sites
- full and partial agonists - inverse agonists - reversible competitive antagonists - irreversible competitive antagonists
59
2 effector regions
- non-competitive antagonists - channel activators

Basic Pharmacology (16 decks)

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