Cholinergic Pharmacology

Question 1

Name the antagonist of all types of muscarinic ACh receptor

Answer 1

Atropine.

Question 2

What is the difference, in terms of antagonism, between muscle nACh receptors and ganglionic nACh receptors?

Answer 2

muscle nACh receptors are potently blocked by tubocarine whereas ganglion nACh receptors require high concentration of tubocarine to block them.

Question 3

Name a potent antagonist of the nACh receptors of the autonomic ganglia

Answer 3

Hexamethonium

Question 4

What pharmacological effect does Carbachol have?

Answer 4

It is a muscarinic agonist (also nicotinic to an extent). It is used experimentally.

Question 5

What muscarinic agonist is used for the treatment of bladder and Gastrointestinal hypotonia?

Answer 5

Bethanechol. It Is a selective muscarinic agonist

Question 6

What effects does Pilocarpine have?

Answer 6

it stimulates the mACh receptors in the iris sphincter muscles and the cilliary muscles of the eye. The contraction of these aid drainage of the Aqueous Humour so Pilocarpine is useful for treatment of Glaucoma.

Question 7

Which muscarinic receptor is Cevimeline selective for?

Answer 7

The M3 muscarinic receptor. This receptor is found on salivary glands so stimulation increases secretion. This effect is used to treat Sjorgen Syndrome

Question 8

Name three antagonists of mACh receptors

Answer 8

Atropine, Hyoscine and Homatropine

Question 9

What do the antagonists of mACh receptors have in common in terms of their chemical structure?

Answer 9

They tend to be tertiary bases. The are similar to ACh as they contain an ester and basic group. Instead of the acetyl group they have an aromatic group.

Question 10

What are the 4 general effects of mACh antagonists in the periphery?

Answer 10

1) Block of secretions
2) Tachycardia
3) Pupillary Dilation
4) Relaxation of smooth muscle

Question 11

What effect does Atropine have on the CNS?

Answer 11

In large doses, it has a stimulatory effect on CNS. Causes restlessness, disorientation and hallucination

Question 12

What are the clinical uses of Atropine?

Answer 12

• Used alongside anaesthesia to prevent vagal inhibition
• Treatment of Bradycardia
• Treatment of GI hypermotility

Question 13

What effect does Hyoscine have on the CNS?

Answer 13

It is a CNS depressant. It causes sleep and amnesia.

Question 14

What are the clinical uses of Hyoscine?

Answer 14

• Used prior to anaesthesia to block secretions and to cause drowsiness
• Used following eye surgery to prevent contraction of the pupil and ciliary muscle

Question 15

What are the clinical uses of Homatropine?

Answer 15

• Used to dilate the pupil and paralyse the lens for examination