Antagonist which generates an action opposite to a substance but by binding to the different receptors is known as:
**Core Concept**
The question is testing the understanding of the mechanism of action of antagonists, specifically those that generate an opposite action to a substance by binding to different receptors. This concept is crucial in pharmacology, as it helps in understanding how different drugs interact with receptors to produce their desired effects.
**Why the Correct Answer is Right**
The correct answer is an inverse agonist. An inverse agonist is a type of antagonist that binds to the same receptor as the agonist but generates an action opposite to that of the agonist. This is achieved by stabilizing the receptor in a conformation that is opposite to the active conformation of the agonist, thereby producing an effect that is opposite to that of the agonist. For example, in the case of G-protein coupled receptors, an inverse agonist can decrease the activity of the receptor, leading to an opposite effect compared to an agonist that increases the activity of the receptor.
**Why Each Wrong Option is Incorrect**
**Option A:** Competitive antagonist - This is incorrect because a competitive antagonist competes with the agonist for the same receptor but does not generate an opposite action. Instead, it reduces the effect of the agonist.
**Option B:** Non-competitive antagonist - This is incorrect because a non-competitive antagonist reduces the effect of the agonist by binding to a different site on the receptor, but it does not generate an opposite action.
**Option C:** Partial agonist - This is incorrect because a partial agonist is a type of agonist that produces a partial response compared to a full agonist, but it does not generate an opposite action.
**Clinical Pearl / High-Yield Fact**
Inverse agonists can be useful in treating conditions where the agonist is not effective or is even harmful. For example, in the case of GABA receptors, inverse agonists can be used to treat anxiety disorders by decreasing the activity of the receptor.
**Correct Answer:** C. Inverse agonist.