Hello,
Serotonin is the coolant for the nervous system running from brain and all throughout body. It balances and counteracts the hyperactivite energizing qualities of dopamine, adrenaline and noradrenaline system, or the "Fight or Flight" response. Serotonin happens to be involved in many other mechanisms in the body, such as good mood, appetite, temperature regulation, sleep, and digestion to name a few.
Dopamine may or may not be a malfunction in the Tourettes case. There may simply not be enough serotonin to calm the very driven, sensitive, energetic and stimulated personality of an individual. The "soul", or drive behind the thoughts in some people isn't so aggressive in life, and therefore when their serotonin is low, they are reclined in their bodies and don't push beyond. Touretters on the other hand keep going, so the brain tries to brake, but it can't, dopamine activity is fueled by thoughts. So then the mind needs to let off the steam through emergency break, tics.
Serotonin is made from an essential animo acid L-Tryptophan. Since this is the most deficiency amino acid in our society (because 8 other amino acids compete with it for absorption), we need to supplement with pure L-tryptophan along with B-6, Vit. C and magnesium to help production.
Taking 5-Htp supplements bypasses the rate limiting steps in serotonin production and is not advisable in my opinion, since body cannot regulate it precisely.
Also, dopamine neurons can "malfunction" due to overwhelming oxidative stress. Increasing antioxidants would help this.
Heavy metals such as lead, mercury, inorganic iron, cadium, aluminum, etc can also interefere with normal nerve transmission.
Intestinal dysbiosis, Candida, and other bacterial infections are directly involved in neurotoxicity and the byproducts they release into the bloodstream are direct nerve irritants and should be eliminated.
But each person needs a custom and comprehensive approach. What I mentioned are the most obvious and logical starting points.
Good luck ,
Igor M.
Healing Advisor