8)Receptor mediated + Non receptor mediated mechanisms of drug actions

Question 1

Receptor

Answer 1

• Specific molecules in biological systems w/which drugs interact to change the function of a system
• They are proteins
• Drugs act as agonists/antagonists to certain receptors
• Agonists ⇢ Stimulate + activate response
• Antagonist ⇢ stop agonists from stimulating the receptors

Question 2

Affinity

Answer 2

• Determines how tightly a drug binds to a receptor

Intrinsic activity

• Measure of the ability of a bound drug to generate an effect

Question 3

Ionotropic receptors

Answer 3

• Involved in fast synaptic transmission
• Ligand gated ion channel receptors:
• As ligand binds ⇢ allows opening/closing of channel
• Eg: nACh receptors, GABA receptors

Question 4

G-Protein coupled receptors

Answer 4

• Comprised of 7 membrane spanning segments
• Largest segment interacts w/G-protein to cause action inside the cell
• Eg: adrenergic receptors, mACh receptors

Question 5

Tyrosine-Kinase receptors

Answer 5

• Have tyrosine kinase enzyme
• Kinase controls ⇢ phosphorylation, cell growth + cell differentiation
• Eg: Insulin receptors

Question 6

Intranuclear receptors

Answer 6

• Lipophilic drugs diffuse through cell membrane + bind to receptors in cytosol
• They translocate to nucleus + upregulate/downregulate gene transcription
• Via actions on specific sections of DNA

Question 7

Non - Receptor mediated mechanisms

Answer 7

By chemical action:

• Neutralisation - anti acids
• Chelation - EDTA, Dimercaprol + Penicillamine
• Ion exchangers - Cholestyramine exchanges Cl- from bile salts

By Physical action

• Osmosis
• Absorption
• Protectives
• Demulcents - menthol in cough syrups
• Astringents
• Saturation in a bio-phase - General anaesthesia