L-Arginineis a semi-essential amino acid that has shown promise in the prevention of atherosclerosis (blockage of the arteries). L-arginine is pure 100%free form arginine and is the precursor for endothelium-deprived nitric oxide (EDNO). A team of Three scientists were awarded the Nobel Prizein Medicine in 1998 for discovering nitric oxide’s role as a vasodilator. In a healthy endothelium (inner wall of a blood vessel),nitric oxide will keep vessels pliable and elastic, dilate (open up)blood vessels keeping blood flowing smoothly, relax blood vessels, keep platelets and white blood cells calm and prevent them from sticking to the vessel wall, prevent oxidation, slow plaque growth, suppress atherosclerosis and melt away plaque that already exists.
Afterarginine is consumed in foods and in supplements, it makes its way into the bloodstream and circulates throughout the body. As it enters the endothelial cells that line the smooth muscle walls of blood vessels,an enzymatic reaction occurs that converts arginine to nitric oxide,which in turn can have a dramatic and positive effect on your cardiovascular health.
There are over 75,000 medically published clinical studies attesting to the fact that arginine will:
- help lower blood pressure
- improve memory and cognitive functions
- improve sexual function
- improve diabetes
- lower cholesterol and triglycerides
- improve congestive heart failure
- reduce blood clots and strokes
- improve wound healing
- improve liver and kidney function
- improve human growth hormone (HGH)
- improve muscle growth and performance
and much more.
So what's the main reason it's put into Smart Energy Drinks? Well probably that it makes you feel good when your blood vessels are relaxed and blood is flowing smoothly. I'm guessing that's the main reason. All the rest is just a bonus.
Here's a pdf of a doctor's report on L-Arginine
Phenylethylamine or P.E.A. has (according to wikipedia) been shown at least indirectly to satisfy the fourmain criteria required to demonstrate that a neuroamine sustains mood and that its deficit can be responsible for depression. In fact, antidepressant drug therapy is an indirect (pharmacological) "replacement" of brain... 
