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Pharmacology > Patrick Hadoke > Flashcards

Patrick Hadoke Flashcards

1
Q

name the receptor in the effector organ of the sympathetic nervous system

A

adrenoreceptors

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2
Q

where does the alpha-1,2 beta-1,2 adrenoreceptors located in the SNS?

A

alpha 2: nerve terminal involve in NA uptake

alpha 1, beta- 1,2: effector organ and mediate effect

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3
Q

name three drugs that target the synthesis of NA and state what they treat

A
  • methyldopa: anti-hypertensive in pregnant woman
  • alpha-methyl-tyrosine: tumour (phaeochromocytoma)
  • carbidopa: Parkinson’s disease
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4
Q

name which G protein each adrenoreceptor is associated with, name their second messenger and what effect does it have

A
  1. alpha-1 + Gq/11: activates PLC which produces IP3 -> smooth muscle contraction
  2. alpha-2 + Gi: act through inhibiting adenylate cyclase -> decrease cAMP -> decrease [Ca2+]i inhibition of transmitter release
  3. beta-1-3 + Gs: do the opposite of Gi therefore causes heart muscle contraction, smooth muscle relaxation and glycogenolysis
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5
Q

what action is mediated by endogenous agonist NA and Adr acting on its receptors?

name their unwanted side effects

A

NA (alpha 1,2 and beta 1): increase BP

Adr (alpha 1,2 and beta 1,2): bronchodilation, increase BP and HR

side effects: hypertension, vasoconstriction, tachycardia

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6
Q

name two drug targets for indirect sympathomimetics

A
  • inhibit MAO

- inhibit uptake 1

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7
Q

name drugs that inhibit uptake 1 and MAO

A

uptake 1:

  • cocaine
  • tricyclic antidepressant e.g. imipramine

MAOI:
-amphetamines

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8
Q

name three drugs that are able to displace NA through uptake 1

A
  • tyramine
  • amphetamine
  • ephedrine

all these drugs can displace NA and stimulate sympathetic NS but due to the methyl substitution, decreases binding affinity

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9
Q

name the side effects of indirect sympathomimetics

A
  • hypertension
  • convulsion
  • dependence
  • cheese reaction (MAOI only) - interaction with food
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10
Q

what would be the effect of cheese reaction?

A

drastic increase of neurotransmitter in the cleft -> over activation of the sympathetic NS -> vasoconstriction -> increased HR -> hypertenstion

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11
Q

where is the alpha-1 receptor located?

A

smooth muscle cell (cardiovascular system and lower urinary tract)

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12
Q

name two alpha-1 agonists and state its action and the receptor it targets

name their side effects

A

methoxamine -> alpha 1 and 2 -> vasoconstriction

phenylephrine -> alpha 1 -> vasoconstriction

side effects: hypertension and reflex bradycardia

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13
Q

name three alpha-1 receptor antagonists, name its target, action, clinical use and unwanted side effects

A

phenoxybenzamine -> alpha-AR and Uptake 1 (non-sel, irrev) -> vasodilation -> pheochromocytoma (tumour)

prazosin -> alpha -1 AR -> vasodilation -> antihypertensive

tamsulosin -> alpha 1A AR -> relax urinary system -> blocks constriction of urethra

unwanted side effects:

  • hypotension
  • tachycardia
  • nasal congestion
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14
Q

describe the effect mediated by activation of alpha-2 receptors and named the second messenger affected

A

when stimulated, alpha-2 receptors block adenylate cyclase hence generation of cAMP -> prevent Ca2+ influx -> prevent release of neurotransmitters

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15
Q

name a partial agonist and antagonist of alpha-2 receptors

A

clonidine - former antihypertensive -> but causes hypotension, oedema and drowsiness

yohimbine -> hypertension or excitement

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16
Q

where is the beta 1 adrenoreceptor located in the body and which second messenger does it use?

A

cardiac myocyte

uses AC -> cAMP causes contraction of the heart muscle

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17
Q

name a beta-1 receptor agonists, state its action and clinical use, name its side effect

A
  • dobutamine
  • positive ionotropy
  • cardiogenic shock
18
Q

where is the beta-2 receptors located?

A

smooth muscle cell: vein, skeletal muscle artery or bronchiole

19
Q

name a beta-2 receptor agonists, name its uses and side effects

A

isoprenaline (non selective) -> asthma

salbutamol (beta-2) -> asthma

side effects: peripheral vasodilation, tremor, dysrythmias

20
Q

name three beta receptors antagonists, its target receptor, action and clinical use. name the side effects

A
  1. propanolol (b1 and 2) -> negative inotropy -> angina, hypertension, cardiac arrythmia, anxiety
  2. atenolol (metoprolol) -> b1 selective -> same as propanolol
  3. nebivolol -> b1 and increase NO -> positive inotropy and vasodilation -> hypertension

side effects: bronchoconstriction, cardiac failure, depression

21
Q

how do beta antagonists exert its anti-hypertensive effect?

A
  1. decreases CO
  2. vasodilation
  3. CNS effects -> decrease sympathetic act
  4. blocks the RAAS system which is associated with vasoconstriction, salt retention, hypertrophy
22
Q

how does b antagonists contribute in preventing heart failure?

A

blocks sympathetic drive -> causes vasodilation -> prevention of cardiac hypertrophy -> maintain CO

23
Q

name a drug used to treat glaucoma targeting the beta-2 receptor what is its mechanism of action?

A

timolol -> release of humour -> decrease pressure

24
Q

name the features of the alpha subunit of G proteins

A

alpha:

  • hydrolyses GTP back to GDP (GTPase domain)
  • provides binding surface for GBgamma and effector proteins
25
Q

describe what happened to G proteins when agonist binds to GPCRs (general pathway)

A
  1. agonist binds
  2. change loop structure cause high affinity binding for G protein
  3. GDP dissociates replace with GTP
  4. dissociation of the protein trimer
  5. active form of g-protein diffuse freely in the membrane and associate with other enzymes/ion channels
  6. attachment of alpha subunit increases its GTPase activity
  7. hydrolysis of GTP -> GDP
26
Q

name the second messenger used to mediate the action of these G proteins:

Gs
Gi/o
Gq
G12

A
  1. AC
  2. AC
  3. Rho
  4. PLC
27
Q

name the enzyme that breaks down cAMP

A

PDEs hydrolyse it into 5’-AMP

28
Q

describe how isoprenaline could cause muscle relaxation (arterial)

A
  1. isoprenaline binds to b1 receptor
  2. stimulates adenylate cyclase to convert ATP -> cAMP
  3. cAMP activates PK (PKi -> PKa)
  4. PK phosphorylates MLCK -> MLCK-P -> relaxation
29
Q

name the receptor in which clonidine binds to and what is its effect?

A

a2 receptor -> inhibits cAMP which causes contraction through unphosphorylated MLCK

30
Q

which enzymes does cAMP and cGMP is broken down with?

A

cAMP - PDE3 and 4

cGMP - PDE5

31
Q

which enzyme does rolipram targets? and what does it treat?

A

PDE4 in the treatment of asthma to cause relaxation of smooth muscle

32
Q

what is the substrate for the membrane phospholipid PLC?

A

PIP2

33
Q

which type of receptors uses Gq protein?

A

M3 and alpha1

34
Q

explain how activation of PLC in the smooth muscle cell lead to increase in [Ca2+]

A

activation of PLC cleaved PIP2 to release IP3.

IP3 interacts with IP3R (ligand-gated calcium channel) to control release of Ca2+ from intracellular storage

35
Q

apart from PIP2 what other protein does DAG interact with and activate?

A

membrane bound PKC which phosphorylates other proteins (perhaps IP3 -> IP4)

36
Q

which receptor and G protein mediates the relaxation and contraction of blood vessels?

A

M3 and Gq

37
Q

what happened to the response if you rub the inner surface of the vessel and when you expose your tissue to NA?

A

rub inner surface: contraction

without rubbing: relaxation

38
Q

ach can both relax and contract smooth muscle. explain this phenomenon

A

the arterial wall is made up of two cells: endothelium nd smooth muscle cell

when rubbed from the inside, Ach interacts with M3 receptors on the surface of the smooth muscle cell -> increases [Ca2+] -> contraction

without rubbing Ach stimulates M3 receptors on the surface of endothelium -> entry of Ca2+ into cell -> converts L-Arg to NO -> No diffuse to smooth muscle cell -> act through GC -> causes relaxation

39
Q

what is the name of the calcium-dependent enzyme in the endothelium?

A

NO-synthase which produces NO

40
Q

how does NO causes relaxation of the smooth muscle?

A

NO causes activation of GC -> concerts GTP to cGMP -> phosphorylate PKG -> relaxation

Pharmacology (8 decks)

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