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Mesoprefrontal dopaminergic neurons: can tyrosine availability influence their functions?
1Department of Pathology, Beth Israel Hospital, Harvard Medical School, Boston, MA 02215, USA.
Biochemical Pharmacology
|February 21, 1997
Summary
Dopamine (DA) neuron functions in the prefrontal cortex (PFC) depend on tyrosine. Supplementing tyrosine can impact cognitive functions, working memory, and stress responses, particularly in certain conditions like PKU and schizophrenia.
Area of Science:
- Neuroscience
- Biochemistry
Background:
- Dopamine (DA) neurons projecting to the prefrontal cortex (PFC) are crucial for cognitive functions, including working memory and stress response.
- These DA neurons are implicated in the pathophysiology of schizophrenia.
- The role of tyrosine, a precursor amino acid, in the function of mesoprefrontal DA neurons is under investigation.
Purpose of the Study:
- To review the evidence for tyrosine dependence of mesoprefrontal DA neurons.
- To explore the impact of tyrosine availability on PFC functions in both animal models and humans.
- To understand how tyrosine supplementation affects cognitive processes and DA neuron activity under various physiological conditions.
Main Methods:
- Review of existing studies in rats using models of experimental diabetes and phenylketonuria (PKU).
- Analysis of human studies investigating tyrosine levels and PFC functions.
- Examination of tyrosine's effects on cognitive tasks, including working memory and smooth-pursuit eye movements, under stress and in patient populations.
Main Results:
- Reduced brain tyrosine levels in animal models significantly alter DA neuron physiology and function.
- Tyrosine supplementation enhances DA neuron outflow only when activity is high and regulation is compromised.
- Human studies show impaired cognitive functions in PKU patients with low tyrosine and altered eye movements in schizophrenic patients with tyrosine supplementation.
- Tyrosine administration improved working memory in humans after cold stress.
Conclusions:
- Mesoprefrontal DA neuron function is demonstrably influenced by tyrosine availability, especially under specific physiological challenges.
- Tyrosine's impact on PFC functions highlights its importance in cognitive processes and neurological conditions.
- Further research is warranted to elucidate the precise mechanisms and therapeutic potential of tyrosine modulation in brain function.