Question

Which one of the following is a competitive antagonist at benzodiazepine site of GABA- receptor gated chloride channel?

• A. Muscimol
• B. Picrotoxin
• C. Flumazenil
• D. Beta-carboline (DMCM)

Answer 1

The Correct Option is C

The question involves identifying a competitive antagonist at the benzodiazepine site of the GABA_A receptor gated chloride channel. Let us analyze each provided option to determine the correct answer:

1. Muscimol: It is a potent agonist of the GABA_A receptor. Muscimol binds to the GABA binding site and not to the benzodiazepine site. Thus, it does not act as a competitive antagonist at the benzodiazepine site.
2. Picrotoxin: It is a non-competitive antagonist that acts at the GABA_A receptor by blocking the chloride ion channel. It does not act specifically at the benzodiazepine binding site.
3. Flumazenil: This is a well-known competitive antagonist specifically at the benzodiazepine receptor site of the GABA_A receptor. It is used in clinical settings to reverse the effects of benzodiazepines in cases of overdose.
4. Beta-carboline (DMCM): Beta-carbolines are known to act as inverse agonists at the benzodiazepine site, meaning they have an opposite effect to agonists on the GABA_A receptor. However, they are not explicitly competitive antagonists.

From the above analysis, Flumazenil is the only option that acts as a competitive antagonist at the benzodiazepine site of the GABA_A receptor. Therefore, the correct answer is:

Flumazenil