What neurotransmitter is secreted by parasympathetic boutons?

What neurotransmitter is secreted by parasympathetic boutons?

• A. Glutamate
• B. Acetylcholine
• C. Epinephrine
• D. Histamine

Answer: (B)

The neurotransmitter secreted by parasympathetic boutons is acetylcholine. This is because the parasympathetic nervous system primarily utilizes acetylcholine as its neurotransmitter at both preganglionic and postganglionic synapses. Acetylcholine binds to nicotinic receptors in the ganglia and to muscarinic receptors on the target organs, facilitating the "rest-and-digest" responses characteristic of parasympathetic activation.

In contrast, glutamate is primarily involved in excitatory neurotransmission in the central nervous system, epinephrine is primarily released by sympathetic postganglionic neurons and plays a key role in the "fight or flight" response, and histamine is associated with immune responses and signaling in the central nervous system but is not a neurotransmitter of the parasympathetic system. Thus, acetylcholine is the definitive answer regarding parasympathetic neurotransmission.