Neurotransmitter release and receptor actions
In this lesson, we'll cover the somewhat complicated process of neurotransmitter release, as well as discuss some effects drugs can have when they bind to neurotransmitter receptors (we'll talk more about specific drugs later in the course).
1) Start with this video about neurotransmitter release:
2) Then, watch this video about the general effects drugs can have on neurotransmitter (and other) receptors:
3) Finally, answer these questions to test your understanding:
1. When an action potential reaches the synaptic boutons, it triggers the influx of which ion that is essential for neurotransmitter release?
- A. Potassium
- B. chloride
- C. magnesium
- D. calcium
Show Answer
Correct answer: D
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated calcium channels. The resulting calcium influx helps mobilize synaptic vesicles, preparing them for neurotransmitter release.
2. Which family of proteins is primarily responsible for getting synaptic vesicles ready to fuse with the presynaptic membrane during neurotransmitter release?
- A. SNARE proteins
- B. neurofilaments
- C. voltage-gated potassium channels
- D. kinesin motor proteins
Show Answer
Correct answer: A
SNARE proteins (including synaptobrevin/VAMP, syntaxin, and SNAP-25) form a complex that docks and primes synaptic vesicles and then drives membrane fusion during neurotransmitter release.
3. A drug binds to a serotonin receptor, activates it, and causes a response, but the response is only a fraction of what is caused when serotonin binds to the receptor. What is the term used to describe this type of drug action?
- A. partial agonism
- B. agonism
- C. antagonism
- D. inverse agonism
Show Answer
Correct answer: A
Agonism occurs when a drug binds to a receptor and causes a biological response. Agonists that can generate a maximal response at a receptor are called full agonists. Partial agonists are only able to generate a fraction of the possible response at a receptor.
4. Naloxone (Narcan) is a drug that can be administered to treat and potentially reverse the effects of an opioid overdose. It works by blocking opioid receptors (the receptors opioid drugs bind to), as well as by displacing opioid drugs that are already attached to the receptor. Naloxone's mechanism of action is best described as:
- A. antagonism
- B. agonism
- C. allosteric modulation
- D. inverse agonism
Show Answer
Correct answer: A
Naloxone is a competitive antagonist at opioid receptors, which means that it works by binding to the same receptors that opioid drugs bind to, but instead of activating those receptors like opioid drugs, naloxone blocks activity at them. Naloxone also causes opioid drugs that are already attached to the receptor to be displaced.
5. A drug binds to a site on the serotonin receptor that is distinct from the serotonin binding site. This binding increases the likelihood that serotonin will bind to the receptor and activate it. Which mechanism below best describes the mechanism of action of this drug?
- A. agonism
- B. antagonism
- C. allosteric modulation
- D. inverse agonism
Show Answer
Correct answer: C
Allosteric modulators bind to a receptor at a different site from where an agonist binds and influence the function of the receptor. Allosteric modulators can increase or decrease the likelihood of an agonist binding to a receptor, enhance or reduce the effects an agonist has when it does bind, or activate the receptor on their own.
