This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Intravenous Anesthetic Agents, Subject name: Anaesthesia
All of the following acts on GABA receptor except 
Select and explain. 
A. Propofol, B. Thiopentone, C. Etomidate, D. Dexmedetomidine
D: Dexmedetomidine
Answer: D: Dexmedetomidine 
Explanation: Dexmedetomidine acts on alpha 2 -adrenoceptor. propofol , thiopentone and etomidate acts on GABA receptor ketamine acts on NMDA receptor