Tyrosine: effects on catecholamine release.

摘要: Tyrosine administration elevates striatal levels of dopamine metabolites in animals given treatments that accelerate nigrostriatal firing, but not untreated rats. We examined the possibility amino acid might actually enhance release animals, technique measuring metabolism was too insensitive to demonstrate such an effect. Dopamine assessed directly, using brain microdialysis extracellular fluid. (50-200 mg/kg IP) did indeed cause a dose related increase fluid with minor elevations DOPAC and HVA, its major metabolites, which were dose-related. The rise short-lived, suggesting receptor-mediated feedback mechanisms responded increased by diminishing neuronal firing or sensitivity tyrosine. These observations indicate measurement changes if negative, need rule out increases release.