Making neurotransmitters: precursors and rate-limiting steps
Explains why transmitters must be made inside the brain, and how drugs like L-DOPA shortcut the process.
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- Distribution: membranes, protein binding and barriers — Transmitters are polar, so they can't cross the blood-brain barrier.
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- Dopamine: receptor families, clearance and pathways — Tyrosine → DOPA → dopamine.
- When enzymes change: induction, inhibition and genetics — Carbidopa blocks peripheral breakdown of L-DOPA — an enzyme inhibition you'll see again.
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Neurotransmitters must be synthesized within the brain – within presynaptic neuron itself, because NTs themselves can’t cross into or out of the brain. Start with a dietary precursor that can cross into the brain, then metabolized into NT within. Some step of this chemical reaction is rate limiting, which determines how fast new NT can be synthesized.
Términos del curso
Las palabras de tu profesor, tal cual aparecen en las diapositivas. Aprende el término y esta definición; la explicación de abajo solo ayuda a entenderla.
- Neurotransmitter
“Molecules released from presynaptic neurons that bind to receptors on pre/postsynaptic neurons”Diapositivas 03, p. 16
Rapidly reuptaken/metabolized after release.
- Dietary precursor
“Start with a dietary precursor that can cross into the brain, then metabolized into NT within”Diapositivas 03, p. 16
NTs don't pass through the blood-brain barrier, so the brain builds them from precursors that do.
- Rate limiting step
“Some step of this chemical reaction is rate limiting”Diapositivas 03, p. 16
The slowest step; it “determines how fast new NT can be synthesized”.
- Tyrosine hydroxylase
“Tyrosine into DOPA is rate limiting (tyrosine hydroxylase)”Diapositivas 03, p. 22
The rate-limiting enzyme for dopamine and norepinephrine.
- L-DOPA (levodopa)
“Levodopa (L-DOPA) can be taken to “shortcut” this process and boost DA levels in brain”Diapositivas 03, p. 22
Parkinson's treatment; taken with a peripheral AADC inhibitor so it isn't converted before reaching the brain.
- 5-HTP
“Tryptophan into 5-HTP is rate limiting”Diapositivas 03, p. 27
The rate-limiting step for serotonin (enzyme: tryptophan hydroxylase).
De tu curso: Course slides 03, pp. 16, 22, 27
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