What are natural/holistic ways of stimulating or increasing norepinephrine in the brain?

Tyrosine: Some feel that stress depletes catecholamine neurotransmitters such as norepinephrine in the brain.Tyrosine is a precursor for the synthesis of catecholamines, norepinephrine, epinephrine, and dopamine. Mental well-being is much more complex than any one neurotransmitter, but supplemental tyrosine may increase ne levels in the brain. Nausea, headache, fatigue, heartburn & arthralgias may come too.