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Pharmacology 1A > Pharmacology of the ANS > Flashcards

Pharmacology of the ANS Flashcards

1
Q

What are the 3 methods of neurotransmitter elimination from the synaptic cleft?

A
  • Re-uptake
  • Diffusion
  • Breakdown
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2
Q

Why is neurotransmitter elimination from the synaptic cleft important?

A

It prevents receptor desensitisation in the post-synaptic membrane.

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3
Q

Which post-synaptic receptors are faster: ionotropic receptors or metabotropic receptors?

A

Ionotrophic Receptors

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4
Q

What type of post-synaptic receptors are GPCRs?

A

Metabotrophic Receptors

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5
Q

Give 2 examples of drugs that target voltage-gated Na+ to inhibit the signal.

A

Lignocaine (local anaesthetic)
Phenytoin (used to treat epilepsy, which is over-excitation)

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6
Q

Give an example of a drug that targets voltage-gated Ca2+ to inhibit the transmitter release.

A

Ziconotide (experiemental drug to treat neuropathic pain).

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7
Q

Give an example of a drug that targets inhibition of exocytosis.

A

Botulinum toxin A – ‘Botox’:
Blocks exocytosis of acetylcholine. Involved in balancing muscle tone in cerebral palsy, treatment of hypersecretory disorders.

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8
Q

Give an example of a drug that targets presynaptic transmitter uptake.

A

Fluoxetine - blocks pre-synaptic uptake of serotonin.

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9
Q

Which named drug do I need to know that effects Parasympathetic Activation of ACh M2 muscarinic Receptors in the Heart?
How does it work?

A

**Atropine **is a non-selective muscarinic antagonist (can antagonist at ALL muscarinic receptors) used in treatment of bradycardia.
M2 Receptors are Gi coupled - inhibit adenylyl cyclase, active K+ channels, hyperpolarising the membrane of muscle cells, reducing rate of contraction.
Would be administered i.v.

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10
Q

Which named drugs do I need to know that effect Sympathetic Activation of NA β1-muscarinic Receptors in the Heart?

A
  • Adrenaline
  • Isoprenaline
  • Dobutamine
  • Propanolol
  • Atenolol
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11
Q

How can adenaline be used as an agonist at NA β-muscarinic Receptors in the Heart?

A
  • Used in treatment of cardiac arrest (i.v. - unless circulation has stopped, then intracardially (directly into the heart)).
  • Only selective for adrenoreceptors (any sub-type).
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12
Q

How can isoprenaline be used as an agonist at NA β-muscarinic Receptors in the Heart?

A
  • Treatment of shock (now rarely used).
  • It is a non-selective β adrenoreceptor agonist (will work on all β adrenoreceptors).
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13
Q

How can dobutamine be used as an agonist at NA β-muscarinic Receptors in the Heart?

A
  • Selective for β1 receptors
  • Use to treat cardiac arrest, cardiogenic shock, cardiac surgery.
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14
Q

How can propanolol be used as an antagonist at NA β-muscarinic Receptors in the Heart?

A
  • Treatment of angina, arrhythmia, recovery from myocardial infarction, hypertension. Effect depends on prevalent sympathetic tone: very little at rest. With exercise, decrease of cardiac output.
  • Side effects: bradycardia, cold extremities, risk of bronchoconstriction.
  • Non-selective β-antagonists.
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15
Q

How can atenolol be used as an antagonist at NA β-muscarinic Receptors in the Heart?

A
  • Treatment of cardiovascular disease, and symptoms of anxiety (peripheral and central effect).
  • Specific to β1 receptors.
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16
Q

What type of GPCRs are sympathetic NA β1receptors in the heart?

A
  • Gs coupled
  • Increase cAMP signalling.
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17
Q

What type of GPCRs are sympathetic NA α1Receptors in Vascular Smooth Muscle? What types of smooth muscle are they found in?

A
  • Gq-coupled, increase Ca2+ (contraction).
  • Skin, GI tract and kidney vascular smooth muscle
18
Q

What type of GPCRs are sympathetic NA β2 receptors in Vascular Smooth Muscle? What types of smooth muscle are they found in?

A
  • Gs increasing cAMP, relaxation.
  • Heart, brain, lungs and skeletal muscle vascular smooth muscle
19
Q

Which named drug do I need to know that effects Parasympathetic Activation of ACh M3 Muscarinic Receptors in Vascular Endothelial Cells?
How does it work?

A

Glycerol Trinitrate:
- A nitric oxide donor, lowers blood pressure to treat rapid onset angina.
- ACh M3 Muscarinic Receptors are Gq-coupled, increase intracellular Ca2+.
- Stimulates nitric oxide (very membrane-permeable signalling molecule) production in endothelial cells.
- Indirectly relaxes vascular smooth muscle.

20
Q

Which named drugs do I need to know that effect Sympathetic Activation of Noradrenaline / Adrenaline α1 and β2 Receptors in Vascular Smooth Muscle?

A
  • Adrenaline (agonist)
  • Phenylephrine (agonist)
  • Phentolamine (antagonist)
  • Prazosin (antagonist)
21
Q

How can adenaline be used as an agonist at NA α1 and β2 Receptors in Vascular Smooth Muscle?

A
  • To treat anaphylaxis (i.m.) and to prolong actions of local anaesthetics via local vasoconstriction.
  • It is a non-selective agonist, slightly less α-selective than NA.
22
Q

How can phenylephrine be used as an agonist at NA α1 and β2 Receptors in Vascular Smooth Muscle?

A
  • Treatment of acute hypotension.
  • Over The Counter nasal decongestant.
  • Systemic side effects: hypertension - and reflex bradycardia.
  • An α1 –selective agonist.
23
Q

How can phentolamine be used as an antagonist at NA α1 and β2 Receptors in Vascular Smooth Muscle?

A
  • Control of hypertension in phaeochromocytoma (adrenal tumour - the tumour may be caused uncontrolled release of adrenaline).
  • Reversible competitive α-antagonist.
24
Q

How can prazosin be used as an antagonist at NA α1 and β2 Receptors in Vascular Smooth Muscle?

A
  • Antihypertensive.
  • Side effects: postural hypotension, headache, reflex tachycardia.
  • α-antagonist
25
Q

Which named drug do I need to know that effects parasympathetic Activation of ACh M3 Muscarinic Receptors in the Airways?
How does it work?

A

Ipratropium: Agonist drug that can be inhaled to treat asthma through muscle relaxation.
- ACh M3 Muscarinic Receptors are Gq coupled - activating PKC and subsequent increase in intracellular Ca2+

26
Q

Which named drugs do I need to know that effect Sympathetic Activation of Noradrenaline β2 Receptors in Smooth Muscle of Trachea and Bronchi?

A
  • Salbutamol (β2 –selective agonist: β2 > β1): Anti-asthmatic by inhalation, short acting. Also used as tocolytics, i.e. to inhibit premature labour.
  • Salmeterol (β2 –selective agonist: β2 > β1): Anti-asthmatic by inhalation, longer term action.
  • Receptors are Gs-coupled (increasing cAMP, relaxation).
27
Q

How does a parasympathomimetic drug work?

A

Agonist drug that activates PNS receptors.

28
Q

How does a sympatholytic drug work?

A

Antagonist drug that blocks sympathetic action relative to parasympathetic action.

29
Q

Which parasympathetic receptors are activated in digestion? What effect does this produce?

A
  • ACh activates M3 muscarinic receptors (Gq-coupled) in gastro-intestinal smooth muscle.
  • Contraction, increasing peristalsis, food is moved along GI tract.
  • ACh activates M1 and M3 muscarinic receptors in GI tract glands:
  • Stimulates secretion of saliva and stomach acid.
30
Q

Which drugs are agonists / antagonists at ACh M3 and M1 receptors in PNS involved in digestion?

A
  • Pilocarpine: Parasympathomimetic agonist drug that activates M3 receptors -> increase in saliva production.
  • Bethanechol: Parasympathomimetic agonist drug that activates M3 receptors -> increase of peristalsis in GI tract.
  • Atropine, hyoscine: Non-selective antagonists at muscarinic receptors: Used to reduce secretions (e.g. preparing patient for surgery).
  • Pirenzepine: M1 antagonist used to reduce acid secretion in stomach (formerly used in treatment for peptic ulcers).
31
Q

Which sympathetic receptors are activated in digestion and metabolism? What effect does this produce?

A
  • NA activates α and β receptors in liver and adipose tissue:
  • Glycogenolysis.
  • Gluconeogenesis.
  • Lipolysis (fat mobilisation).
  • NA activates β2 receptors in the GI tract:
  • Relaxation of smooth muscle: decreased peristalsis.
32
Q

What is a drug that affects sympathetic activation of receptors involved in digestion and metabolism? How does it work?

A

Clenbuterol: sympathomimetic agonist doping agent (banned in competitive sports): activates β2 adrenoreceptors increasing muscle mass and speed of contraction in skeletal muscles, increasing lipolysis in adipose tissue, increased bronchodilation.

33
Q

Which receptors are involved in parasympathetic activation of the bladder? How do they work?

A
  • ACh activates M3 muscarinic receptors (Gq-coupled) in the bladder detrusor muscle.
  • Smooth muscles contract promoting bladder emptying.
34
Q

Which drugs are agonists / antagonists at ACh M3 receptors in PNS in the bladder?

A
  • Bethanechol: parasympathomimetic agonist drug activating M3 receptors, assisting bladder emptying.
  • Darifenacin: parasympatholytic M3 antagonist, used in treatment of urinary frequency, urgency and incontinence.
35
Q

Which receptors are involved in sympathetic activation of the bladder? How do they work?

A
  • NA β2 adrenoreceptors in detrusor muscle (Gs-coupled), causing relaxation.
  • NA α1 adrenoreceptors in sphincter muscle (Gq-coupled) contraction.
  • Overall effect preventing urination.
36
Q

What is a drug involved in sympathetic activation of receptros in the bladder? How does it work?

A

Prazosin sympatholytic α1 antagonist that increases urinary flow by relaxing sphincter muscle - used particularly in benign prostatic hyperplasia.

37
Q

What is midriasis?

A
  • Widening of the pupil.
  • Occurs in sympathetic activation of receptors in the eye.
  • Midriasis hinders intraocular fluid drainage.
38
Q

What is miosis?

A
  • Pupil constriction.
  • Allows better near vision.
  • Occurs in parasympathetic activation of receptors in the eye.
  • Helps with intraocular fluid drainage.
39
Q

Which parasympathetic receptors are activated in the eye? How do they work?

A
  • Gq-coupled ACh M3 muscarinic receptor circular iris muscle. → constriction of pupil (miosis)
  • Gq-coupled ACh M3 muscarinic receptors in ciliary muscle (sphincter muscle - contraction causes lens to bulge allowing better near vision).
40
Q

Which drugs are involved in parasympathetic activation of receptors in the eye?
How do they work?

A
  • Atropine: - parasympatholytic antagonist of M3 muscarinic receptors, eye drops to cause mydriasis and cycloplegia (paralysis of the ciliary muscle) for up to 7 days. Can be used in eye examinations. Recipients will struggle with focusing close up.
  • Tropicamide: (up to 6 hours - otherwise same as atropine action).
41
Q

Which receptors are activated by the SNS in the eye?
How do they work?

A
  • NA activates α1-adrenoreceptors (Gq-coupled) in the radial dilator pupillae muscle, leading to contraction, the pupil widens (mydriasis).
  • Useful in flight-or-flight as increases light sensitivity and gives a wider field of vision.
  • NA activates β-adrenoreceptors (Gs-coupled) in epithelium at ciliary body, stimulating increased production of intraocular fluid.
  • NA activates α1-receptors (Gq-coupled) in the iris radial muscle - mydriasis may hinders fluid drainage (iris is thicker).
  • Overall increased intraocular pressure (increased production of fluid and decreased drainage).
42
Q

What is glaucoma? How does it occur? How is it treated?

A

Glaucoma is chronically raised intraocular pressure above 21mmHg. Can damage optic nerve - potentially causing blindness. It results from imbalances in production and drainage of fluid in the eye.

  • Pilocarpine: muscarinic parasympathomimetic drug (lowers intraocular pressure).
  • Timolol: Non-selective β-adrenoreceptor antagonist (sympatholytic).

Pharmacology 1A (5 decks)

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