Which of the following is NOT listed as a method for receptor identification?

• A. Structure-Activity Relationship (SAR)
• B. Binding of radioactive ligand
• C. Molecular cloning
• D. Patch-clamp electrophysiology

Answer: (D)

The key idea is how receptors are identified using biochemical and molecular approaches rather than purely functional electrical measurements. Structure-Activity Relationship helps map what chemical features a ligand needs to bind a receptor, linking chemical structure to receptor interaction. Binding of a radioactive ligand directly identifies receptor presence and properties by showing specific, saturable binding that defines receptor density and affinity. Molecular cloning reveals the receptor’s gene sequence, confirming its identity and allowing expression studies to validate its role.

Patch-clamp electrophysiology, while powerful for characterizing how ions flow through channels and how ligands modulate those currents, isn’t used to identify receptors themselves. It’s a functional technique that evaluates channel activity after a receptor has already been identified or when studying the properties of ion channels, rather than a method to discover or confirm receptor identity.