Wk9 Pharmacology Revision Qs

Question 1

What is the family of ligand-gated ion channels mediating autonomic transmission and where in autonomic nervous system are they? What happens to a target cell (such as neurone) when such receptors are activated by an agonist?

Answer 1

A1-adrenoceptor - peripheral tissues - increase in IP3/DAG
A2-adrenoceptor - peripheral tissues, decrease in cAMP
B-adrenoceptor, cardiac nodal tissue, increase in cAMP
M1 & M3 - cerebral cortex/gastric/salivary glands, increase in IP3/DAG
M2 - smooth muscle/cardiac tissue, decrease in cAMP

Question 2

What is the key family of GPCRs mediating autonomic transmission and where in autonomic nervous system are they? What happens to target cells (such as neuron) when such receptors are activated by an agonist?

Answer 2

G proteins are located in the cell membrane.

Gq (increased IP3/DAG) Gi(decreased cAMP), Gs (increased cAMP)

Question 3

What are the 5 main types of adrenoceptors? Identify one or two key locations for each, and the effect of activating each of these with an agonist?

Answer 3

A ‘ ‘ 1, A2, B1, B2 and B3. Found in peripheral tissues. A1 = vascular smooth muscle, A2 = brain

Question 4

Where does hexamethonium act, by what mechanism and what are its effects? To what historical use did the drug have and why is it no longer used?

Answer 4

• Neuronal sub-type of nicotiniques receptor
• Blocks ion channel - Na+ can’t move through even though ACh still binds, thereby blocking all effects of autonomic stimulation.
• Used originally to lower blood pressure. No longer used as it stopped both the sympathetic and parasympathetic nervous systems and so was not effective.

Question 5

When would you see muscardine poisoning? How does its mechanism explain the symptoms observed?

Answer 5

• Eating many types of mushrooms.
• Muscarinic agonists mimic the action of ACh on muscarinic receptors. This stimulates the symptoms observed as they are parts of the parasympathetic nervous system.

Question 6

What role has Belladonna and the Calar Bean played in our understanding of drugs that affect parasympathetic transmission?

Answer 6

• Belladonna is an anicholinergic which blocks ACh - shows the effects of the neurotransmitter being blocked by drugs.
• Calar Bean = nicotine
• its effects on the nicotinic receptors.

Question 7

To what clinical use are antimuscarinics put? Link the clinical uses to a physiological function with which the drugs are interfering?

Answer 7

• Astmtha - ipratropium given - reverses it.

Question 8

To what clinical use is adrenaline put? Link the clinical uses, the location and function of adrenoceptors around the body.

Answer 8

• Against anaphaltic shock - increases cardiac output. In a/B adrenoreceptor agonists.

Question 9

Describe the signalling pathways mediated by Gq, Gs, and Gi and how these pathways mediate the actions of adrenoceptors and muscarinic receptors.

Answer 9

Gq - PLC
Gi - Decreased AC
Gs - Increased AC

Question 10

Outline the mechanisms of action of the following drugs on the sympathetic nervous system:

Answer 10

• Cocaine (2 distinct protein targets it directly inhibits the function of)
• Amphetamine
• Monoamine oxidase inhibitors (particularly those affecting MAO-A)