They believe it is associated with dopamine, as well as with the closely related neurotransmitter norepinephrine.

High levels of dopamine are also associated with norepinephrine, which heightens attention, short-term memory, hyperactivity, sleeplessness and goal-oriented behavior.

Epinephrine and dopamine had deleterious effect on oxygen metabolism, while norepinephrine plus low dose of dobutamine improved gastric mucosal perfusion and tissue oxygen utilization.