Drugs And The ANS

Question 1

Which division of the autonomic nervous system has a Cranio-sacral outflow?

Answer 1

Parasympathetic

Question 2

Which division of the autonomic nervous system has short pre-ganglionic and long post-ganglionic fibres?

Answer 2

Sympathetic

Question 3

Which division of the autonomic nervous system has long pre-ganglionic and short post-ganglionic fibres?

Answer 3

Parasympathetic

Question 4

Where do the nerve fibres have cell bodies in the sympathetic nervous system?

Answer 4

In all 12 thoracic sections and first 2 lumbar sections.

Question 5

List the major drug classes acting at cholinergic nerve terminals

Answer 5

Nicotinic cholinoceptor antagonists
Muscarinic cholinoceptor agonists
Muscarinic cholinoceptor antagonists
Cholinesterase inhibitors

Question 6

Give an example of a nicotinic cholinoceptor antagonist and its use

Answer 6

Tubocurarine

Muscle paralysis during anaesthesia

Question 7

Give an example of a muscarinic cholinoceptor antagonist and its use

Answer 7

Hyoscine: anaesthetic premedication

Ipratropium bromide: treat bronchoconstriction in asthmatics

Homatropine/tropicamide: pupillary dilation and paralysis

Question 8

Give an example of a muscarinic cholinoceptor agonist and its use

Answer 8

Pilocarpine:
Treatment of glaucoma
Increased GI motility after surgery
Suppression of atrial tachycardia
Stimulates bladder emptying

Question 9

Give an example of a cholinesterase inhibitor and its use

Answer 9

Edrophonium/physostigimin: treatment of glaucoma, myasthenia gravis

Tacrine/donepezil: treatment of Alzheimer’s

Question 10

List the major drug classes acting on noradrenergic receptors

Answer 10

Selective B1 agonist
Selective B2 agonist
Selective a1 agonist
Selective a2 agonist
a-antagonist
Selective a1 antagonist
B-anatgonists (blockers)

Question 11

Give an example of a selective B1 agonist and its use

Answer 11

Dobutamine:

Positive ionotropy and positive chronotropy

Question 12

Give an example of a selective B2 agonist and its use

Answer 12

Salbutamol: bronchodilation

Question 13

Give an example of a selective a1 agonist and its use

Answer 13

Phenylephrine: nasal decongestants

Adrenaline: local vasoconstriction to reduce the dissipation of anaesthetic

Question 14

Give an example of a selective a2 agonist and its use

Answer 14

Clonidine:

anti-hypertension, act on pre-synaptic receptors to reduce NA release.

Question 15

Give an example of an a-antagonist and its use

Answer 15

Phentolamine:
Peripheral vasodilation to treat peripheral vascular disease. Not used to treat hypertension as they cause postural hypotension

Question 16

Give an example of a selective a1 antagonist and its use

Answer 16

Prazosin:

Treatment for hypertension

Question 17

Give an example of a B antagonist and its use

Answer 17

Propranolol:
Treatment for hypertension, MI, angina.
Unwanted side effect= bronchoconstriction

Question 18

What is a-Methyl-tyrosine used for and how does it work?

Answer 18

Used to block NA synthesis is pheochromocytoma.

Competitively inhibits tyrosine hydroxylase

Question 19

What is a-Methyl-DOPA used for and how does it work?

Answer 19

Reduces NA release.
Taken up by adrenergic nerves and is converted to a-Methyl-noradrenaline, accumulates in the synaptic vesicles of noradrenergic nerve terminals. When released by Ca mediated exocytosis it primarily activates presynaptic a2 receptors which inhibit the VOCC, reducing Ca mediated neurotransmitter release.

Question 20

What is CarbiDOPA used for and how does it work?

Answer 20

Used in combination with L-DOPA to treat Parkinson’s disease.
Inhibits DOPA decarboxylase in the periphery but not in the CNS (does not cross the blood brain barrier).

Question 21

What are adrenergic blocking drugs and why are they rarely used clinically?

Answer 21

They reduce impulse conduction, Ca mediated exocytosis, and repletion of NA from synaptic vesicles.
Not used therapeutically because of major side effects (postural hypotension)

Question 22

What are Indirectly-acting Sympathomimetic Agents (IASAs) and how do they work?

Answer 22

Structurally related to NA.
Recognised and transported into adrenergic terminals by Uptake 1 and taken into synaptic vesicles. The displaced NA can leak into the synaptic cleft by a mechanism unrelated to Ca mediated exocytosis.
The extent that NA leaks into the cleft can be enhanced by inhibition of the NA-degrading enzyme MAO.

Question 23

What are Uptake 1 inhibitors and what are some unwanted side effects?

Answer 23

Inhibit NA uptake. Act as tricyclic antidepressants.

Side effects are tachycardia and cardiac arrhythmias.

Question 24

Which division of the autonomic nervous system has a Thoraco-Lumbar outflow?

Answer 24

Sympathetic