Norepinephrine, also known as noradrenaline, is a neurotransmitter found in the sympathetic nervous system. The sympathetic nervous system stimulates the heart, blood vessels, sweat glands, the large internal organs, and the adrenal medulla in the brain. Like dopamine, norepinephrine has a stimulating effect, fosters alertness, and plays an important regulatory role in long-term memory and learning. It also protects endorphins from being broken down prematurely. Optimal levels of this transmitter can stimulate a sense of wellbeing or even create a euphoric effect in stressful situations. Yet excess norepinephrine can fuel the physiological expressions of fear and anxiety, as may be the case for people who suffer from anxiety disorders.

The amino acid tyrosine, found in high concentrations in cheese, is converted by specific reactions into at least two neurotransmitters - norepinephrine and dopamine. Norepinephrine is produced from dopamine, with the help of the amino acids phenylalanine, lysine, and methionine. Vitamins C and B₆, magnesium, and manganese are important cofactors.