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Pharmacology RCOA > pharmacology basics 2 > Flashcards

pharmacology basics 2 Flashcards

1
Q

Which type of receptors typically show signal amplification?

A

Receptors coupled to enzymes

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2
Q

What secondary responses can ligand binding initiate?

A
  • (De)phosphorylation of peptides
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3
Q

What is affinity?

A

The tenacity/probability to which a drug binds to its receptor. Determines the range of drug conc at steep portion of cone-effect curve

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4
Q

What is the formula for fraction of occupied receptors?

A

F = D / Kd + D

D = Drug
Kd = Dissociation constant

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5
Q

How is Kd and affinity associated?

A

Inverse relationship. Lower Kd = greater drug affinity

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6
Q

Define potency

A

The conc/amount of a drug needed to produce a defined effect

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7
Q

How is potency measured?

A

EC50 - The conc at which a drug produces 50% its maximal response
- Drug with low EC50 = high potency

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8
Q

What type of receptors are inotropic?

A

Ligand-gated

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9
Q

What does Lidocaine bind to?

A

Binds to internal surface of phospholipid cell membrane to Na voltage-gated ion channels leading to inactivation

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10
Q

How does NorAdrenaline work?

A
  • Activates Gq-proteins and Gs-proteins
  • Increases intracellular Ca & cAMP
    -Stimulates alpha-1 adrenoreceptors
  • Positive inotropic/chronotropic effects on beta-1 adrenoreceptors
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11
Q

How does Propofol work?

A
  • Binds to beta subunit of GABA-A
  • Activation results in increase in channel opening allowing inc Cl- entry and cell hyper polarisation
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12
Q

How do opioids affect their receptors?

A
  • G protein coupled receptors linked to inhibitory G proteins
  • Agonists hyperpolarise the cell
  • Reduces levels of cAMP = inhibition of neurotransmitter release
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13
Q

How do Benzos act on receptors?

A
  • Act on allosteric binding sites on inotropic GABA-A (ligand gated)
  • Exert anxiolytic/sedative effects \
  • GABA-B receptors are metabotropic = stimulate K+ conductance = hyper polarising neuronal membrane
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14
Q

What does mass action state?

A

The rate of a reaction is proportional to the conc of the reacting elements

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15
Q

What is the affinity constant?

A
  • The strength of the drug-receptor bond (Ka)
  • Ka = K(on) / K(off)
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16
Q

What is the dissociation constant?

A
  • Reflects tendency drug-receptor complex has to dissociate back to its drug & receptor components (Kd)
  • OR molar conc of a drug when 50% of its receptors are occupied at equilibrium
  • Kd = K(off) / K(on)
17
Q

What is median effective dose?

A
  • ED50
  • Dose of a drug that produces a response in 50% of the population it is administered to
  • Drug with low ED50 = high potency
18
Q

What is intrinsic activity?

A
  • Drugs maximal efficacy as a fraction of the maximal efficacy produced by a full agonist acting on the same receptor under the same conditions
19
Q

What happens if a system has a partial & full agonist at the same time working on the same receptors?

A

Partial agonist will act as a competitive antagonist to the full agonist

20
Q

How does Buprenorphine work?

A
  • Partial agonist at MOP & NOP opioid receptors
  • Analgesic effects at low/middle doses
  • Anti-analgesic effects at high doses
  • Therefore in the presence of Morphine (full agonist) acts as a competitive antagonist
21
Q

What is constitutive activity?

A

Most receptors can signal in the absence of an agonist
Magnitude is dependent on: Conformational flexibility & efficiency which receptor produces system change once activated

22
Q

What is an inverse agonist?

A

A drug which inhibits constitutive activity
Has intrinsic activity -1 - 0

23
Q

What do the action of G-Coupled protein receptors depend on?

A
  • Receptor: 7 transmembrane helices
  • G protein: Heterotrimeric protein of 3 subunits (a, b,y)
  • Effector molecule: Activated by a-subunit , synthesises secondary messengers
24
Q

What are the 3 parts of an enzyme-linked receptor?

A
  • Extracellular ligand-binding domain
  • Transmembrane domain
  • Intracellular ‘active enzyme’ domain (mostly kinases that phosphorylate serine/tyrosine/threonine)
25
Q

Give an example of an enzyme linked receptor

A
  • Insulin
  • Binds to receptor
  • Activates P13K causing GLUT vesicle to bind with Glucose transporter allowing glucose to enter cell
26
Q

Give an examples of drugs that acts on voltage-gated ion channels

A

CCBs
Local anaesthetics
Class III anti-arrhythmics
NA channel blockers

27
Q

Give an examples of drugs that acts on ligand-gated ion channels

A

Muscle relaxants
Induction agents

28
Q

What are the 2 main types of intracellular receptors?

A
  • Type 1: Ligands bind to protein receptors in cytoplasm/nucleus (sex hormone, cortisol, mineralocorticoid)
  • Type 2: Ligands bind directly to DNA (Vit A, D, Retinoid, thyroid)
29
Q

What are the components of intracellular receptors?

A
  • Transcription-activating domain
  • DNA-binding domain (zinc containing loops)
  • Ligand-binding domain
30
Q

What are the types of steroid receptors?

A
  • Oestrogen
  • Progesterone
  • Androgen
  • Glucocorticoid
  • Mineralocorticoid
31
Q

How does steroid hormone receptor activation occur?

A
  • When inactive associated with chaperone proteins (HSP) keeping them stable
  • On hormone binding undergo conformational change
  • HSP dissociates to reveal nuclear localisation sequence allowing passage of complex into nucleus
  • Interacts with HRE via DNA-binding domain
  • Activates gene transcription or silence gene expression
32
Q

How does thyroid hormone receptor activation work?

A
  • Hormone binds to receptor = conformational change
  • DNA-binding domain binds to thyroid response element (TRE) located in promoter region of T3-responsive gene
  • Gene transcription & expression occurs
33
Q

Which channels are more sensitive to general anaesthetic?

A

Ligand-gated ionic (mainly GABAa)

Pharmacology RCOA (12 decks)

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