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Behavioural effects of acute phenylalanine and tyrosine depletion in healthy male volunteers

Grupo de Psicofarmacologia, Departamento de Psiquiatria, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul e Serviço de Psiquiatria, Hospital de Clínicas de Porto Alegre, Porto Alegre; Centro de Memória, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre; Avenida Taquara 586/606, 90460-210, Porto Alegre, RS, Brazil; grevet{at}terra.com.br

Marcos R. Tietzmann

Grupo de Psicofarmacologia, Departamento de Psiquiatria, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul e Serviço de Psiquiatria, Hospital de Clínicas de Porto Alegre, Porto Alegre

Flávio M. Shansis

Centro de Memória, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre

Caroline Hastenpflug

Grupo de Psicofarmacologia, Departamento de Psiquiatria, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul e Serviço de Psiquiatria, Hospital de Clínicas de Porto Alegre, Porto Alegre

Luiz C. Santana

Serviço de Genética do Hospital de Clínicas de Porto Alegre, RS, Brazil

Letícia Forster

Flávio Kapczinski

Grupo de Psicofarmacologia, Departamento de Psiquiatria, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul e Serviço de Psiquiatria, Hospital de Clínicas de Porto Alegre, Porto Alegre

Ivan Izquierdo

Centro de Memória, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre

Acute phenylalanine and tyrosine depletion (APTD) studies have been used to assess the role of the cathecholaminergic system in various aspects of human behaviour. In this study we conducted a randomized, double-blind, controlled and cross-over comparison to evaluate the effects of APTD on memory, attention and mood in normal subjects. Twelve healthy male volunteers were included in this study. The subjects ingested a nutritionally balanced mixture (B) or a similar mixture deficient in phenylalanine and tyrosine (PT^–). Before and 5 h after ingestion of the drink, volunteers underwent tests on mood, memory and attention. Results of the memory tests showed that PT^– mixture impaired word recall as measured in Rey's test (p = 0.016). The assessment of changes in mood showed that the balanced mixture improved scores of as alertness (VAMS factor I, p = 0.037) and the PT^– mixture induces an opposite effect, increased scores of anxiety (Profiles of Mental State composed-anxious dimension, p= 0.022). These results suggest that tyrosine plasma levels and cathecholamines may be important factors in regulating mood and memory.

Key Words: acute depletion • attention • cathecholamine • memory • mood • phenylalanine • tyrosine

Journal of Psychopharmacology, Vol. 16, No. 1, 51-55 (2002)
DOI: 10.1177/026988110201600103


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