SF - Receptor theory

Question 1

What are the molecular targets for drug action? What effect does the drug exert on these targets?

Answer 1

Receptors - transduce signal from drug.
Enzymes - activate or switch off.
Transporters - carry molecules across the membrane.
Ion channels - open or close.
Nucleic acids - affect gene transcription.

Question 2

What is a transporter protein?

Answer 2

Proteins that allow membrane impermeable molecules to enter cells.

Question 3

What is the effect of fluoxetine?

Answer 3

Prevents the reuptake of serotonin at the synapse. This can therefore be targeted by drugs.

Question 4

What are ion channels?

Answer 4

Pores in the cell membrane. Open in response to a voltage or a ligand.

Question 5

What is a receptive substance?

Answer 5

A chemical combination between the drug and constituent of the cell.

Question 6

What are the properties of an ionotropic receptor?

Answer 6

• Responds to a ligand.
• Fast response. (msec)
• Mainly extracellular.
• Loops through the membrane to form pores.
• Formed from many subunits (a,b,g,d)

Question 7

What are the properties of metabotropic receptor?

Answer 7

• GPCR
• 7 transmembrane domains.
• Medium response (sec-min)
• A subunit is bound to GDP. When Pi combines, it forms GTP.

Question 8

What is the function of Gs, Gq and Gi/o

Answer 8

Gs - stimulates adenylate cyclase. Increased cAMP and stimulation of PKA.
Gq - Stimulates PLC and PKC. Increased IP3 and DAG. This leads to calcium release from the ER.
Gi/o - Inhibits adenylate cyclase. Decreases cAMP. bg subunit inhibits calcium channels and activates potassium channels.

Question 9

What are the properties of receptor tyrosine kinases?

Answer 9

Phosphorylation of tyrosine residues in the membrane.

Activates growth factors, cytokines and hormones.

Question 10

What are the properties of DNA-linked receptors?

Answer 10

• Within the cytoplasm.
• Moves to the nucleus when a ligand binds.
• Increase or decreases gene transcription.