This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Pharmacology
[{'content': 'Benzodiazepine binding ste on GABA receptors is on- \nSelect and explain. \nA. g-subunit, B. a-subunit, C. b-subunit, D. d-subunit', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. is \'b\' i.e., a-subunit o The exact subunit structures of native GABA receptors are still are unknown, but it is thought that most GABA receptor are composed of a, b and g subunits that Coassemble with some uncertain stoichiometryo Binding site of GABA is on b-subunit.o Benzodiazepine site is located on the a subunit but the stabilization or completion of that site in the assembled structure also requires the g subunit."The photo-affinity labelling of the benzodiazepine site has confirmed, using isoform - antibodies, to be on an a and not a g subunit". -- Receptor subunit & complexes.o So, BZD binding site is present on a subunit at a - g interface, and both a & g units are required for BZDs action.o Barbiturates act on picrotoxin site that is located usually on b - subunit at a- b interface. Both a & b subunit are required for barbiturates action.o GABA - b - subunito BZD - a subunit at a - g interface, i.e. a/g siteo Barbiturate - b subunit at a- b interface, i.e. a/b site', 'role': 'assistant'}]