Final answer:
Serotonin is the neurotransmitter involved in regulating levels of arousal and mood, affected by Zoloft. Zoloft increases serotonin levels by inhibiting its reuptake in the brain.
Step-by-step explanation:
The neurotransmitter involved in levels of arousal and mood that is influenced by drugs such as Zoloft is serotonin. Serotonin, also known as 5-hydroxytryptamine or 5-HT, is a key monoamine neurotransmitter in the central nervous system (CNS) and plays a significant role in mood regulation, among other functions. Zoloft, an antidepressant, modulates the availability of serotonin by inhibiting its reuptake, thereby increasing serotonin levels and influencing mood and arousal. In contrast, acetylcholine (ACh) is a neurotransmitter that triggers depolarization at motor end-plates, while GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the CNS, and dopamine is another neurotransmitter that influences reward, motivation, and motor control.