Plasma precursors of brain catecholaminergic and serotonergic neurotransmitters in rehabilitation patients with ischemic stroke

OBJECTIVE: To determine levels of plasma amino acid tyrosine and tryptophan, precursors of brain catecholamine and serotonin neurotransmitters, respectively, in rehabilitative patients with ischemic stroke. DESIGN: Controlled, pre-post analysis, consecutive sample. SETTING: Rehabilitation center. PARTICIPANTS: Twenty men with ischemic stroke (age, 68+/-11.3y) consecutively admitted into rehabilitation 15+/-10 days (range, 7-28d) after an acute cerebrovascular insult; 15 healthy sedentary subjects (controls 1); and 13 healthy hypoactive individuals who had recently had knee arthroplasty (controls 2). Both control groups were matched to stroke subjects for age, gender, and body weight. INTERVENTIONS: At 8:00 am, after overnight fasting, venous blood samples were drawn from patients to determine plasma tyrosine and tryptophan levels. A nutritional evaluation, including nitrogen balance, was made. The same procedures were repeated after 45 days of rehabilitation. Amino acid data were compared with those obtained from the controls. MAIN OUTCOME MEASURE: Plasma concentrations of amino acids. RESULTS: Patients with ischemic stroke, on admission, had lower plasma tyrosine concentration than did both controls 1 (P<.0005) and controls 2 (P<.001), but a similar tryptophan level. The plasma content of tyrosine was similar between the 2 control groups. After 45 days of rehabilitation, the stroke patients' tyrosine and tryptophan levels remained virtually unchanged, as did nutritional parameters. Nutritional intakes were adequate to meet body needs but insufficient to correct plasma tyrosine. CONCLUSIONS: Patients experiencing a recent stroke may have low plasma tyrosine levels and, therefore, reduced brain catecholamine formation. It is possible that an imbalance of brain neurotransmitters may occur