NGF is released into plasma during human pregnancy: an oxytocin-mediated response?

The presence of biologically active nerve growth factor (NGF) in the peripheral
circulation of women during pregnancy, labour and lactation was investigated.
Using a sensitive immunoenzymatic assay (ELISA), we found an approximately
five-fold increase in plasma NGF levels during labour and lactation compared with
the concentrations found at the term of gestation or in control healthy women.
Since labour and lactation are characterized by activation of the
hypothalamo-pituitary-adrenal axis and by high plasma levels of the
neurohypophyseal hormone oxytocin, and since the intravenous injection of
oxytocin in female rats causes a 176% increase in the hypothalamic levels of NGF,
it is possible that the increased amount of circulating NGF is correlated with
one or both of these events.