Which statement best describes an inverse agonist?

Which statement best describes an inverse agonist?

• A. Activates receptors more than the agonist.
• B. Only blocks receptor binding without affecting basal activity.
• C. Binds to receptors and reduces their baseline activity in the absence of an agonist.
• D. Increases receptor desensitization without occupancy.

Answer: (C)

The concept being tested is constitutive (basal) receptor activity and how different ligands influence it. An inverse agonist binds to the receptor and shifts the equilibrium toward the inactive state, reducing the receptor’s signaling even when no agonist is present. This is what makes the statement that describes binding to receptors and lowering baseline activity in the absence of an agonist the correct one. This differs from a neutral antagonist, which simply blocks agonist binding without changing the receptor’s basal activity, and from an agonist, which increases signaling. It also isn’t about increasing desensitization without occupancy, since desensitization generally requires some receptor occupancy to trigger the process.

The concept being tested is constitutive (basal) receptor activity and how different ligands influence it. An inverse agonist binds to the receptor and shifts the equilibrium toward the inactive state, reducing the receptor’s signaling even when no agonist is present. This is what makes the statement that describes binding to receptors and lowering baseline activity in the absence of an agonist the correct one.

This differs from a neutral antagonist, which simply blocks agonist binding without changing the receptor’s basal activity, and from an agonist, which increases signaling. It also isn’t about increasing desensitization without occupancy, since desensitization generally requires some receptor occupancy to trigger the process.