A compound binds the benzodiazepine site of the GABA-A receptor and decreases chloride channel opening below the level observed even in the complete absence of any ligand. In recombinant systems the receptor shows constitutive activity. How should this compound be classified?
- A Inverse agonist ✓
- B Partial agonist
- C Competitive antagonist
- D Neutral allosteric modulator
Correct answer: A. Inverse agonist
Explanation
An inverse agonist stabilises the inactive conformation of a constitutively active receptor and reduces signalling below basal (ligand-free) levels. Reducing GABA-C channel opening below baseline produces anxiety and convulsant activity, as seen with beta-carbolines at the benzodiazepine site. C competitive antagonist (option C) blocks ligands but leaves basal activity unchanged. C partial agonist increases signalling above baseline, and a neutral modulator binds without altering activity.
Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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