Which of the following correctly describes GABA-A and GABA-B receptors?

• A. GABA-A is metabotropic; GABA-B is ionotropic.
• B. GABA-A is an ionotropic Cl- channel causing hyperpolarization; GABA-B is a metabotropic GPCR that opens K+ channels and closes Ca2+ channels; both reduce excitability.
• C. GABA-A inhibits neurotransmitter release via second messenger cascades.
• D. GABA-B directly gates Cl- channels.

Answer: (B)