This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Introduction to Central Nervous System, Subject name: Physiology
An example of "autoreceptors" in the CNS is: 
Select and explain. 
A. NMDA receptors for, B. Nicotinic receptors for acetyl chlorine, C. Alpha2 receptors for NE, D. GABA-C receptors in retina
C: Alpha2 receptors for NE
Answer: C: Alpha2 receptors for NE 
Explanation: Autoreceptor is a presynaptic receptor; binding of the NT with autoreceptor inhibits fuher secretion of the transmitter. a2-receptor for NE is an example of autoreceptor. NMDA receptor for glutamate is a voltage + ligand gated channel. Nicotinic AChR is a non-specific cation channel. GABA-C receptors are found exclusively in the retina; they are ionotropic receptors.