Identifying the Mood-Regulating Neurotransmitter

Neurotransmitters play a vital role in the functioning of the nervous system by transmitting signals between neurons. Each neurotransmitter has specific effects on behavior and physiological processes. For example, dopamine is often associated with feelings of pleasure and reward. Understanding their roles can help us comprehend various psychological and physiological disorders. One neurotransmitter, Acetylcholine, is specifically known for its role in muscle contraction and memory function.

Which of the following neurotransmitters is primarily associated with mood regulation and has been implicated in conditions such as depression?