Question

Question 14 1.81 pts A drug binds and activates a receptor of the natural ligand (neurotransmitter). It interferes with the binding site for the principal ligand. Indirect Agonist Indirect Antagonist Direct Agonist Direct Antagonist

Answer 1

Correct answer - Direct Agonist

Explanation

1. An agonist is a drug that mimics the action of the natural ligand
2. Ligand is a molecule that acts on the receptor.
3. A direct agonist is a drug that attaches to the receptor of a natural ligand
4. Besides attaching, it stimulates the receptor to give rise to an effect similar to the primary ligand.
5. That is why it is called a direct agonist
6. Now coming to the second part of the question - the natural ligand is unable to displace the drug.
7. This is because the affinity of the drug for the receptor is more than that of the natural ligand.
8. In other words, the affinity of the drug for the receptor is so strong, that the natural ligand is unable to displace this drug for its receptor.

Indirect Agonist - Incorrect answer -

1. This drug increases the synthesis/ release of the neurotransmitter at the synaptic junction.
2. It is an agonist because it mimics the action of the natural ligand.
3. It doesn't direct interact with the receptor.

Indirect Antagonist - Incorrect answer -

1. A drug that reduces or stops the neurotransmission is called an antagonist.
2. An indirect antagonist reduces the production or release of neurotransmitters at the synapsis or receptor.
3. It doesn't directly interact with the receptor

Direct Antagonist - Incorrect answer -

1. This drug binds to the receptor of a natural ligand and inhibits it. Therefore, it stops neurotransmission.
2. It has no effect on the production or release of the neurotransmitter.