The cholinergic system includes acetylcholine and which other signaling molecules?

• A. Norepinephrine
• B. Dopamine
• C. Neuropeptides
• D. Serotonin

Answer: (C)

Cholinergic signaling is centered on acetylcholine as the primary neurotransmitter. In many pathways, acetylcholine is released together with neuropeptides, which serve as co-transmitters or neuromodulators. Neuropeptides are stored in different vesicles and generally produce slower, longer-lasting effects that shape the overall response to acetylcholine, influence synaptic plasticity, and help regulate autonomic circuits. Because of this co-release, neuropeptides are associated with cholinergic signaling. The other options represent distinct transmitter systems—norepinephrine, dopamine, and serotonin—that operate independently as monoaminergic pathways and are not typically described as part of the cholinergic system. While there can be interactions between systems, the best answer reflects the co-transmitter role of neuropeptides with acetylcholine.