Presence of relatively high concentrations of arginine vasotocin in the cerebrospinal fluid of newborns and infants.

Lumbar cerebrospinal fluid (CSF) was obtained from healthy newborns, infants, and children of both sexes between 23-777 days of age. Bioassay of the CSF revealed relatively high antidiuretic and hydroosmotic activities. Rat uterine activities could be detected only in the CSF of newborns, and these activities were increased in the presence of magnesium. The antidiuretic and hydroosmotic activities of CSF from newborns were significantly higher than the same CSF activities of infants (P less than 0.01) and children (P less than 0.001). No sex differences were observed in the above biological activities of CSF. The ratio of these activities, their susceptibility to tryptic digestion, and the increase of the rat uterine activity by magnesium demonstrate the presence in CSF of a basic peptide indistinguishable from synthetic arginine vasotocin. In contrast to the CSF of healthy newborns and infants, neither antidiuretic nor hydroosmotic activities could be detected in the CSF of a boy, aged 413 days, with a pineal tumor and precocious puberty.