This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Despite the popularity of L-tryptophan manipulation procedures, which can temporarily produce changes in serotonergic levels in the central nervous system, a number of methodological concerns have become evident in psychiatric behavioral research. Most notable is the fact that L-tryptophan balanced formulations, which serve as a control or placebo condition, actually decrease plasma L-tryptophan levels rather than maintaining stable concentrations of circulating L-tryptophan. Data indicates that the amount of L-tryptophan in the current balanced formulation is inadequate and does not truly serve as an inactive placebo formulation. Thus, we propose to compare the traditional formulation to three new amino acid formulations that vary in the amount of L-tryptophan. Healthy normal controls will be recruited and each will consume one of the formulations, hourly blood samples will be drawn to determine changes in plasma L-tryptophan concentrations across the following 7 hours. The overall goal of the proposed study is to determine the amount of L-tryptophan necessary for a balanced placebo that will maintain stable plasma L-tryptophan concentrations across time. Achieving this goal will be a significant methodological improvement, which will be implemented in our NIH sponsored L-tryptophan studies (R01-AA-014988), and this methodological improvement will also considerably change methods used in this area of research.
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