Sites of drug action

Question 1

Most drugs have their site of action at the synapse

Answer 1

Agonists and antagonists - both can be direct or indirect

Question 2

Agonists

Answer 2

Drug that binds to and activates a receptor - allows for more NT to be present: more effect

Question 3

Antagonists

Answer 3

Drug that binds to but does not activate a receptor - less NT: inhibitory effect on NT

Question 4

Direct

Answer 4

competitive bidning: drugs take place where NT would go

• Direct agonist: cause opening of ion channels
• Direct antagonist: not cause ion channels to open

Question 5

Indirect

Answer 5

Noncompetitive binding:

• Receptors have multiple sites to which different ligands can bind
• drug and neurotransmitter can both bind
• Indirect agonist: facilitates ion channels opening
• Indirect antagonists: drugs that attach to binding site and interfere with normal action of the receptor; prevents ion channels from opening

Question 6

Neurotransmitter production

Answer 6

1. nt precursor can be administered, increasing the amount of nt produced and serving as agonist
2. drug can inactivate an enzyme used to make a nt and serve as antagonist

Question 7

NT storage and release

Answer 7

1. storage is accomplished by the same transporter molecules that reuptake nt from synaptic cleft into terminal button
   - these transporter proteins are in the membrane of synaptic vesicles and “pump” nt into the vesicle
   - some drugs can block the transporter protein and the vesicles are empty when they dock and are released
2. some drugs prevent release by deactivating the protein that cause docked vesicles to fuse with presynaptic membrane
3. other drugs have opposite effect and by binding with these proteins (as Ca+ would) and cause release of nt

Question 8

Receptors

Answer 8

1. Some drugs bind to postsynaptic receptors just like NTs do
2. Some receptors have multiple sites to which different ligands can bind: Some for NT, others for hormones or other neuromodulators
3. Drugs can bind to autoreceptors in presynaptic membrane

Question 9

Reuptake and enzyme deactivation

Answer 9

1. nt is inactivated by protein that binds to it and returns it to terminal button
   - drug can bind to the reuptake protein and block its action
2. nt can e broken down by an enzyme
   - drug can inactivate the enzyme