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Basic Pharmacology > 2. Receptors > Flashcards

2. Receptors Flashcards

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
Q

Example of a voltage-gated receptor

A
  • sodium ion channels in nerve cell membranes
  • local anaesthetics work to block these
26
Q

Nicotinic ion channel is what structure?

A
  • pentamer of 5 subunits
  • 2 alpha, a beta, a gamma and a delta
27
Q

Resting vs active state of a nicotinic ion channel

A
  • 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
Q

Clinical use of ACh antagonists

A
  • in skeletal muscle, ACh acts on nicotinic receptor to cause muscle contraction
  • nicotinic ACh receptor antagonists are muscle relaxants to allow surgical procedures
29
Q

2 examples of G protein coupled receptors and what drugs work on them

A
  • alpha/beta adrenoreceptors for epinephrine
  • beta 2 adrenoreceptors for salbutamol
30
Q

G protein coupled receptors are the smallest/largest receptors
How are they structured?

A
  • largest
  • single polypeptide chain with 7 transmembrane helices
  • 3 subunits (alpha, beta and gamma)
31
Q

G protein coupled receptors are slow/fast

A
  • slower than others
  • minutes
32
Q

How is specificity of G-protein coupled receptors achieved?

A
  • through molecular variation in alpha subunits
  • Gs, Gi, Gq and G0
33
Q

What does the Gs protein on G protein coupled receptors do?

A
  • activates adenylyl cyclase
  • activates calcium ion channels
34
Q

What does the Gi protein on G protein coupled receptors do?

A
  • inhibits adenylyl cyclase
  • activates potassium ion channels
35
Q

What does the Gq protein on G protein coupled receptors do?

A

activates phospholipase C

36
Q

What does the Go protein on G protein coupled receptors do?

A

doesn’t have an alpha subunit

37
Q

Explain Gs protein signal transduction

A
  • 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
Q

All subunits of adrenoreceptors are activated by …

A

adrenaline or noradrenaline

39
Q

Response in a particular cell of adrenoreceptor is dependent on …

A

which receptor subtype is expressed

40
Q

What happens to adrenoreceptor alpha 1 when adding adrenaline?

A
  • is the Gq form
  • activates PLC
  • get vasoconstriction
41
Q

What happens to adrenoreceptor alpha 2 when adding adrenaline?

A
  • is Gi form
  • inhibits adenylyl cyclase
  • auto-inhibition of neurotransmitter release
42
Q

What happens to adrenoreceptor beta 2 when adding adrenaline?

A
  • Gs form
  • stimulate adenylyl cyclase
  • bronchodilation
42
Q

What happens to adrenoreceptor beta 1 when adding adrenaline?

A
  • Gs form
  • stimulates adenylyl cyclase
  • accelerated heart rate
43
Q

… is a beta 2 receptor agonist

A

salbutamol

44
Q

… is a beta 1 receptor antagonist

A

atenolol

45
Q

2 examples of kinase-linked receptors

A
  • insulin receptor for insulin
  • tyrosine kinase for imatinib
46
Q

Structure of ‘kinase-linked receptors’

A
  • large extracellular ligand binding domain connected to intracellular domain by single membrane-spanning helix
47
Q

4 things formed by kinase-linked receptors

A
  • receptor tyrosine kinase i.e insulin
  • serine/threonine kinase
  • cytokine
  • guanylyl cyclase-linked
48
Q

3 steps of kinase-linked receptors

A
  • ligand binding
  • dimerisation
  • autophosphorylation
49
Q

How do insulin binding receptors work as kinase-linked receptors?

A
  • 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
Q

2 examples of nuclear receptors

A
  • estrogen receptor for estradiol
  • estrogen receptor for tamoxifen
51
Q

Are nuclear receptors highly expressed?

A
  • 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
Q

Nuclear receptors are a family of … … receptors

A

48 soluble

53
Q

2 classes of nuclear receptors

A
  • class 1 (in cytoplasm, forming homodimers, ligands are endocrine - steroids, hormones)
  • class 2 (in nucleus, form heterodimers, ligands are lipids - fatty acids)
54
Q

Binding to … in nuclear receptors creates … changes

A

hormone response elements
Gene transcription changes - pos or neg

55
Q

Explain nuclear receptor class 1 signal transduction

A
  • 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
Q

Most receptor operated channels have single/multiple binding sites. Explain

A
  • 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
Q

3 types of allosteric sites

A
  • positive
  • negative
  • allosteric antagonists
58
Q

4 types of orthosteric sites

A
  • full and partial agonists
  • inverse agonists
  • reversible competitive antagonists
  • irreversible competitive antagonists
59
Q

2 effector regions

A
  • non-competitive antagonists
  • channel activators

Basic Pharmacology (16 decks)

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