Question

All of the following receptor sub-types are ionotropic, EXCEPT ______

A) AMPA glutamatergic.
B) nicotinic cholinergic.
C) kainate glutamatergic.
D) GABAA
E) muscarinic cholinergic.

Answer 1

Muscarinic cholinergic receptors are the only ones mentioned that are not ionotropic; they are metabotropic receptors that work through G proteins and second messengers, unlike the others which form ion channels.

Step-by-step explanation:

All of the following receptor sub-types are ionotropic, EXCEPT E) muscarinic cholinergic. Ionotropic receptors, such as NMDA, AMPA, and kainate glutamatergic receptors, directly form ion channels through the membrane that open in response to a neurotransmitter, allowing ions such as Na+ and Ca2+ to enter the cell. In contrast, muscarinic cholinergic receptors are metabotropic receptors that activate a cascade of intracellular events through G proteins and second messengers when acetylcholine binds to them, which may indirectly lead to the opening or closing of ion channels.