Which neurotransmitter regulates sleep, mood, attention, and learning, and too little of this neurotransmitter can cause depressed mood?

Serotonin and Dopamine

Dopamine is a neurotransmitter which is usually associated with attention and learning, and too of it little can be related to several forms of depression.  

Also, Serotonin plays a part in the development of mood, appetite and is associated with sleep, whereas; too little of serotonin is related to depression.

the consumer demand because the members have to be aware if people are going to buy what they want to sell in this case either energy drinks or a car wash.