EFFECT OF VALINE ON 5-HT-MEDIATED PROLACTIN-RELEASE IN HEALTHY-VOLUNTEERS, AND ON MOOD IN REMITTED DEPRESSED-PATIENTS

Background. Animal experimental studies suggest that the amino acid va line may decrease brain serotonin (5-HT) function by inhibiting the tr ansport of the 5-HT precursor, L-tryptophan, across the blood barrier. The aim of the present study was to assess whether valine could decre ase brain 5-HT function in healthy subjects and provoke symptomatic re lapse in recently remitted depressed patients taking antidepressant dr ug treatment. Method. We studied the effect of valine (30 g) on the pr olactin (PRL) response to the 5-HT releasing agent, D-fenfluramine, in healthy male subjects and on the mood of 12 remitted depressed patien ts taking either selective serotonin re-uptake inhibitors (n=10) or li thium and amitriptyline (n=2), Results. Valine significantly lowered t he PRL response to D-fenfluramine in healthy subjects. in the remitted depressives, valine caused a mild but detectable lowering of mood on a number of measures but only one patient experienced a significant re lapse in mood. Conclusions. Valine administration may decrease brain 5 -HT neurotransmission in humans. This effect could explain the mild in crease in depressive symptoms in patients taking 5-HT-potentiating dru gs.