Norepinephrine neurotransmitter increase

Norepinephrine or noradrenaline is a hormone and a neurotransmitter; it is secreted by the adrenal medulla as a hormone into the blood, and as a neurotransmitter from neurons. Along with epinephrine (adrenaline), another hormone secreted by the adrenal medulla, norepinephrine is involved in the fight-or-flight response to physical or mental stress, directly increasing heart rate, triggering the release of glucose from energy stores, and increasing skeletal muscle readiness, among other actions.

Questions
Q. I have read information you have posted on the Internet for the last few years and have found it extremely useful. I have a question that no person, physician or company has an answer too. Is there a supplement or medication that raises the norepinephrine levels in the body without the use of central nervous system stimulants? Stimulants prescribed by a physician, and over the counter supplements only last for a few days. Medications effecting other neurotransmitters (i.e. seretonin) at the same time as effecting norepinephrine makes them counter productive. If there is any way to raise norepinephrine levels by itself, I am sure this will help my energy level.
   A. I am aware of the amino acid tyrosine leading to an elevation of norepinephrine and the amino acid phenylalanine. Energy levels in the body are influenced by a host of factors, not just the levels of one substance. As such, I don't see the need to focus on one neurotransmitter levels. One should rather focus on a number of natural ways to improve energy.