Beta-carboline derivatives act at the benzodiazepine binding site on the GABA-A receptor and produce anxiety and seizures, the opposite of diazepam. This pharmacological behaviour is classified as:

• A Inverse agonism ✓
• B Competitive antagonism
• C Functional antagonism
• D Partial agonism

Explanation

The GABA-B receptor shows constitutive activity even without ligand. An inverse agonist binds the same site as the agonist but stabilises the inactive conformation, reducing basal signalling and producing effects opposite to those of the agonist. Beta-carbolines at the benzodiazepine site are the classic example, causing anxiety and proconvulsant effects. B competitive antagonist such as flumazenil blocks diazepam but has no intrinsic activity of its own, so it would neither sedate nor provoke anxiety.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

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