Effects of pregnancy and delivery on the availability of plasma tryptophanto the brain: relationships to delivery-induced immune activation and early post-partum anxiety and depression

Background. There is now evidence that the availability of plasma tryptopha n is decreased during pregnancy and the puerperium and also in patients wit h major depression and inflammation. The aims of the present study were to examine: (i) the effects of pregnancy and delivery on plasma tryptophan and the amino acids known to compete for the same cerebral uptake mechanism (C AAs), valine, leucine, tyrosine, phenylalanine and isoleucine; (ii) the rel ationships between the availability of plasma tryptophan and postpartum dep ression or anxiety; and (iii) the relationships between the availability of plasma tryptophan to the brain and inflammatory markers, such as serum int erleukin-6 (IL-6), interleukin-1 receptor-antagonist (IL-1RA) and the leuka emia inhibitory factor receptor (LIF-R). Methods. The above variables were measured in 13 healthy non-pregnant and i n 98 pregnant women 3 to 6 days before delivery and 1 and 3 days after deli very. On each occasion the parturient women completed the state version of Spielberger State-Trait Anxiety Inventory (STAI) and the Zung Depression Ra ting Scale (ZDS). Results. Plasma tryptophan and the tryptophan/CAA ratio were significantly lower at the end of term and after delivery than in the plasma of non-pregn ant, healthy women. The tryptophan/CAA ratio was significantly lower in the early puerperium than at the end of term. There were no significant relati onships between the availability of plasma tryptophan and either post-partu m depression or changes in the STAI or ZDS scores in the early puerperium. The changes in the tryptophan/CAA ratio from the end of term to the early p uerperium were significantly and inversely related to serum IL-6, IL-1RA an d LIF-R. Conclusions. The results show that the reduction in the availability of pla sma tryptophan from the end of term to the early puerperium is related to i mmune activation: and that the lowered availability of plasma tryptophan is not related either to depressive or anxiety symptoms in the early puerperi um or to post-partum depression ensuing some months later.