Sympathetic drugs

Question 1

State the location, effect and endogenous ligand of α₁ adrenoreceptors

Answer 1

Location - smooth muscle , arteries/veins , anal sphincter, bladder

effect - contraction

endogenous ligand - noradrenaline, postganglionic sympathetic nerves

Question 2

State the location, effect and endogenous ligand of α₂ adrenoreceptors

Answer 2

Location - sympathetic nerve varicosities , CNS

effect - inhibitions of noradrenaline release/sympathetic nervous system (act as a negative feedback mechanism)

endogenous ligand - noradrenaline, postganglionic sympathetic nerves, noradrenaline central nerves

Question 3

State the location, effect and endogenous ligand of β₁ adrenoreceptors

Answer 3

Location - heart

effect - increased HR/conduction velocity/contractility

Endogenous ligand - noradrenaline from postganglionic sympathetic nerves

Question 4

State the location, effect and endogenous ligand of β₂ adrenoreceptors

Answer 4

Location - smooth muscle , arteries/veins, bronchial smooth muscle

effect - relaxation

Endogenous ligand - adrenaline from adrenal medulla

Question 5

Describe how β₂ receptors act to relax smooth muscle?

Answer 5

Activation of β₂ receptors leads to increase in [cAMP]

MLCK (myosin light chain kinase) is phosphorylated = relaxation

Question 6

Describe how α₁ receptors act to cause smooth muscle contraction

Answer 6

Activation of α₁ receptors leads to release of Ca²⁺ intracellular stores

Ca²⁺ binds with Calmodulin (Cal)

Ca²⁺Cal complex binds to MLCK = contraction

Question 7

State 3 uses of directly acting sympathomimetics such as adrenaline

Answer 7

to treat cardiac arrest/septic shock/sepsis - β₁ stimulation leads to increased heart earth and cardiac output

to treat anaphylactic shock which is caused by excessive histamine release which leads to bronchospasm ; intravenous adrenaline = bronchodilation via β₂ receptors ; increased HR/CO via β₁ ; increased blood pressure via peripheral vasoconstriction via α₂

Question 8

Indirectly acting sympathomimetic drugs

Briefly describe the action of NA reuptake inhibitors

Answer 8

Reuptake of noradrenaline by neurones limits the duration of its action

NA reuptake inhibitors prolong its action at target receptors, leading to heightened sympathetic excitation (Tachycardia, vasoconstriction and hypertension)

Question 9

Uses of NA reuptake inhibitors

Answer 9

Tricyclic antidepressant (TCA) is used to treat depression and other affective disorders (Long term effect)

Question 10

What does tachycardia mean

Answer 10

HR > 100bpm

Question 11

Where is noradrenaline stored ?

Answer 11

Nerve endings

Question 12

Desribe the action of the indirectly actin sympathomimetics cocaine and amphetamine

Answer 12

Cocaine:

addictive CNS stimulant - block reuptake of both dopamine and noradrenline = heightened sympathetic excitation

amphetamine:

taken up by neurones and causes exocytosis of lots of NA

Question 13

Name an example of adrenoceptor antagonists

Answer 13

Propanolol is a non-selective β blocker ; reduces resting heart rate and improves cardiac output

Question 14

What should you remember when prescribing β blockers?

Answer 14

If β₂ receptors are blocked, bronchoconstriction can occur and be fatal in asthmatics

therefore β blockers must not be prescribed to asthmatics

Question 15

describe 2 of the main therapeutic uses of α₁ antagonists

Name 3 examples and describe the major side effect associated

Answer 15

First use

To promote vasodilation and reduce hypertension

examples : doxazosin and prazosin

postural hypotension - leads to dizzines when standing up

Second use

treat impaired bladder function due to benign prostatic hypertrophy

tamsulosin is specific to bladder α adrenoreceptors so helps improve bladder emptying

Question 16

which two adrenoceptors are found in the smooth muscle of vessels (tunica media)

Answer 16

beta 2 (relaxation) and alpha 1 (contraction)