We adapted a high-performance liquid chromatographic method with electrochemical detection (Clin Chim Acta 1984;139:1-12) to the determination of platelet serotonin. We used this method to determine platelet serotonin reference values in a healthy population, measuring platelet serotonin concentration in the following subjects: 31 newborns (16 girls, 15 boys); 41 children (11 girls, 30 boys), ages 20 months to 15 years; 56 adults (26 women, 30 men), ages 20 to 58 years; and 20 elderly subjects (16 women, four men), ages 65 to 94 years. There was no significant difference in platelet serotonin concentration between sexes in each age group. However, significant changes (P less than 0.001) were observed between the newborns (mean +/- SD: 1.67 +/- 0.74 nmol/10(9) platelets) and the children (4.09 +/- 1.04) or the adults (3.81 +/- 0.87). Moreover, the platelet serotonin concentration in the elderly subjects (2.57 +/- 1.12) was significantly (P less than 0.001) lower than in the adults and children and significantly higher (P less than 0.01) than in the newborns. Such age-related differences must be taken into consideration when data from neurological or psychiatric patients and control subjects are compared.

Dysfunctions of the serotonergic system are implicated in psychiatric disorders, and there is evidence that a familial element may be significant in childhood autism. The concentrations of platelet 5-HT and free and total plasma tryptophan were determined in healthy pregnant women at each month of pregnancy and, at delivery, in both maternal and umbilical cord blood. A significant rise in the level of platelet 5-HT occured during month 3 and 4 followed by a retum to normal from month 5 until the delivery. The level of total plasma tryptophan remained equal to that in normal healthy non pregnant women until the 6th month. By month 7, it had decreased significantly and remained low until the month 9. At delivery the level fell significantly by -41%. The concentration of free tryptophan varied widely from one month to another but there was a trend towards a progressive increase from month 1 to 9, and at delivery the level returned to basal values. The concentration of 5-HT in the umbilical cord blood was about half that of the maternal blood. Inversely the concentrations of both free and total plasma tryptophan in the umbilical cord blood were nearly twice that of the maternal blood.