All diagrams in supply, synthesis and cofactors
Amino acid supply and brain entry
Supply, transport and synthesis are separate control points. A blood level or dietary increase does not directly measure a synapse.
Amino acid supply and brain entry
Scoped educational mechanism
Open larger diagram · Full-size PNG · Diagram page
Read the diagram explanation and sources
Amino acids are supplied by diet and protein turnover. Brain entry is regulated by transporters, including LAT1, which transports several large neutral amino acids as part of an exchange system. Circulating abundance, transport competition, intracellular supply, enzyme activity and transmitter handling must be distinguished. More dietary precursor does not guarantee more transmitter released at a relevant synapse. The LAT1 experimental source includes mouse studies and human rare-variant observations, not a dietary ADHD treatment trial.
- Dietary protein → Circulating amino acids: absorption
- Circulating amino acids → Brain entry: transport
- Brain entry → Inside cells: availability
- Inside cells → Transmitter synthesis: enzyme action
- Transmitter synthesis → Synaptic availability: additional steps
What the diagram shows
Amino acids are supplied by diet and protein turnover. Brain entry is regulated by transporters, including LAT1, which transports several large neutral amino acids as part of an exchange system. Circulating abundance, transport competition, intracellular supply, enzyme activity and transmitter handling must be distinguished. More dietary precursor does not guarantee more transmitter released at a relevant synapse. The LAT1 experimental source includes mouse studies and human rare-variant observations, not a dietary ADHD treatment trial.