Amino Acid Control of Neurotransmitter Synthesis and Release: Physiological and Clinical Implications

Abstract

Brain catecholamine and serotonin neurons are intimately involved in a number of physiological functions such as cardiovascular regulation, neuroendocrine secretion, regulation of behavior, mood and appetite control. The synthesis and release of these neurotransmitters appear to be remarkably correlated with the subsequent physiological changes observed. While there are numerous pharmacological approaches that affect the neurotransmitters involved (i.e., the catecholamines dopamine, noradrenaline and adrenaline as well as the indoleamine serotonin), one particularly attractive (while specific) approach involves the administration of a precursor amino acid. It is thus a prerequisite for the physiological and possibly therapeutic properties of the precursor amino acids l-tyrosine and l-tryptophan that they affect synthesis and release of their transmitter product. We will describe in detail the nature of the different neurochemical mechanisms guiding transmitter synthesis and their dependent physiological responses, in particular appetite control and neuroendocrine regulation.

Potential role of tryptophan and chloride in the inhibition of human myeloperoxidase

“…In addition of its potential capacity to inhibit MPO, its supplements have been thought to keep good health, act as an antidepressants, relieving poor mood and irritability, reduce the cravings for carbohydrates, provide a relief of chronic pain and the symptoms of manic behavior, and normalize sleep [53,66,67]. Tryptophan serves as a biosynthetic precursor for a wide variety of indole-containing metabolites, which are involved in a large and essential number of physiological functions [68]. For example, it increases levels of serotonin on the brain as well as melatonin [69].…”

Acute administration of nutritionally sourced tryptophan increases fear recognition

“…3 Mean€SEM efficiency at recognising emotional facial expressions in healthy female subjects who were randomly allocated to receive either nutritionally sourced TRP or placebo. Significantly greater than placebo, ***P=0.007; *P<0.06 to competing branch chains was significantly increased which would be expected to enhance the availability of TRP for brain 5-HT synthesis (Bender 1985;Young 1986;Lehnert and Wurtman 1993). In a previous study, we found that the pharmacokinetic profile of 1 g of the nutritionally sourced TRP was very similar to that found following 1 g of pure tryptophan given as "Optimax" tablets (unpublished observations).…”

Aromatic amino acids in weight‐recovered females with anorexia nervosa

“…1 Monoaminergic neurotransmitters, in particular noradrenaline (NA), dopamine (DA), and serotonin (5-HT) contribute to the regulation of eating and feeding behavior. [2][3][4] Vice versa the synthesis of brain monoamines is strongly influenced by nutrition and the availability of precursor amino acids in the bloodstream. 3 In the past three decades, our knowledge regarding the role of the aromatic amino acids (AAA) tryptophan (TRP), tyrosine (TYR), and phenylalanine (PHEN) in the brain monoamine synthesis has further expanded.…”