Whole-blood 5-HT was examined in thirty-five depressive patients not on antidepressants, and in comparable control subjects. The concentration of whole-blood 5-HT was significantly lower during depression, but returned to normal after clinical recovery.

Summary The human fetus of 38 to 41 weeks' gestation has a whole blood 5‐hydroxytryptamine (5‐HT) concentration equivalent to the adult. It is suggested that the fetus in utero is capable of producing 5‐HT in sufficient amounts to account for the documented rise in placental 5‐HT concentration found in late pregnancy.

In the course of a study on endogenous depressive illness, whole blood 5-hydroxytryptamine (5HT) has been recorded in sixteen in-patients at Roffey Park Hospital. Thirteen patients received L-tryptophan 1 G t.d.s. and 3 G nocte, of whom two received in addition phenelzine 15 mg. b.d. for 48 hours followed by 30 mg. b.d. thereafter. Three patients received amitriptyline 25 mg. b.d. and 50 mg. nocte for 48 hours followed by 50 mg. b.d. and 75 mg. nocte thereafter. One patient receiving Ltryptophan had essential hypertension and received α-methylDOPA throughout. Observation continued for six weeks.