What neurotransmitter is involved in arousal and mood regulation?

The neurotransmitter that plays a significant role in arousal and mood regulation is norepinephrine. Norepinephrine is involved in the body's response to stress and helps regulate attention and response actions. It is crucial in the 'fight or flight' response, enhancing alertness and readiness, which contributes to arousal states. Additionally, norepinephrine is associated with mood regulation and has been implicated in mood disorders such as depression and anxiety.

Dopamine, while also related to mood and motivation, primarily influences reward processing and is not solely responsible for arousal. Serotonin is known for its role in mood stabilization and emotional regulation, but it does not primarily mediate arousal. Glutamate serves as the main excitatory neurotransmitter in the brain but is less directly involved in the specific processes of arousal and mood regulation compared to norepinephrine. Therefore, norepinephrine is the correct choice as it directly influences both arousal and mood.