Which chemical is described as increasing arousal and may be involved in mania?

The correct choice is norepinephrine, which is a neurotransmitter associated with the body's arousal and alertness responses. Norepinephrine plays a crucial role in regulating mood and emotional responses, and its levels can significantly influence energy, arousal, and enthusiasm.

In the context of mania, elevated levels of norepinephrine can contribute to heightened energy and increased emotional reactivity, characteristic of manic episodes in bipolar disorder. This neurotransmitter's impact on alertness and arousal makes it a significant factor in mood regulation and psychiatric conditions where these symptoms are pronounced.

Understanding the role of norepinephrine highlights its importance in the physiological processing of emotional states and how it can affect behavior in states of mania, thus providing a clear connection between this chemical and the experience of increased arousal.