This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'Which drug acts through alpha subunit of GABA ? \nSelect and explain. \nA. Benzodiazepine, B. Barbiturate, C. Haloperidol, D. TCA', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e., Benzodiazepine 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 y subunits that Coassemble with some unceain stoichiometry. o Binding site of GABA is on beta-subunit. o Benzodiazepine site is located on the alpha subunit but the stabilization or completion of that site in the assembled structure also requires the y subunit. "The photo-affinity labelling of the benzodiazepine site has confirmed, using isoform - antibodies, to be on an alpha and not a y subunit". -- Receptor subunit & complexes. o So, BZD binding site is present on a subunit at alpha - y interface, and both a & y units are required for BZDs action. o Barbiturates act on picrotoxin site that is located usually on beta- subunit at alpha - beta interface. Both alpha & beta subunit are required for barbiturates action. GABA ---> beta - subunit BZD ---> alpha subunit at a - y interface, i.e. a/g site Barbiturate - ---> beta subunit at alpha - beta interface, i.e. a/b site', 'role': 'assistant'}]