CHAPTER 4: SITES OF DRUG ACTION Flashcards
What is an antagonist drug?
-A drug that opposes or inhibits the effects of a particular neurotransmitter on the postsynaptic cell.
What is an agonist drug?
A drug that facilitates the effects of a particular neurotransmitter on the postsynaptic cell
In the case of the administration of an agonist drug, how is synthesis of the NT affected? (give context and then explain)
- Context: many NT are synthesized from precursors.
- When precursor serves as agonist: rate of synthesis and release of NT is increased
In the case of the administration of an antagonist drug, how is synthesis of the NT affected? (give context and then explain)
- Context: steps of synthesis of NT are controlled by enzymes.
- Antagonist drug inactivates one of the enzymes
- Prevents the NT from being produced
What are the different steps of transmission when an agonist drug is administered?
(diagram on this)
- Drug serves as precursor
- Drug stimulates release of NT
- Drug stimulates postsynaptic receptors
- Drug block autoreceptors which increases the synthesis and release of NT
- Drug blocks reuptake
- Drug inactivates acetylcholinesterase
What are the different steps of transmission when an antagonist drug is administered?
- Drug inactivates synthetic enzyme which inhibits the synthesis of NT
- Drug prevents storage of NT in vesicles
- Drug inhibits release of NT
- Drug stimulates autoreceptors which inhibits synthesis and release of NT.
- Drug inhibits release of NT
- Drug blocks postsynaptic receptors.
How do antagonist drug act on presynaptic vesicles in the presynaptic cleft? (context and explanation)
- Context: vesicles are filled with transporter molecules
- Drug molecules bind to a particular site on the transporter and inactivate it.
How does an antagonist drug act on the release of NT?
-Deactivate the proteins that cause synaptic vesicles to fuse with the presynaptic membrane and expel their contents into the synaptic cleft.
What is the most important and complex site of action in the nervous system?
On receptors
How does a direct agonist act on receptors?
- mimics the effects of a neurotransmitter
- molecules of drug attahc to normal binding site of NT
- receptors function just as they do with NT
- ions can pass and produce postsynaptic potential.
What is a direct agonist?
-Drug that binds and activates a receptor
What is a receptor blocker/direct antagonist?
- A drug that binds with a receptor but doesn’t activate it.
- Prevents the natural ligand from binding with the receptor.
How do receptor blockers/ direct antagonists act on receptors?
- Bind to receptor but don’t open ion channel or trigger anything
- They occupy receptors binding site and prevent NT from binding.
How does an indirect antagonist act on receptors? (context and explanation)
- Context: some receptors have multiple binding sites.
- Both drug molecules and NT can bind on same receptor
- Drug attaches and prevents ion channels from opening.
What is noncompetitive binding?
Binding of a drug to a site on a receptor that doesn’t interfere with the binding site for the principal ligand.
