Substance P concentrations in human cerebrospinal fluid vary inversely with age.

The mean concentrations of immunoreactive substance P in cerebrospinal fluid (CSF) of 10 fetuses (gestational age 11-20 weeks) were 22.7 +/- 8.3 pmol/ml, compared with 250.0 +/- 28.2 fmol/ml in premature babies (gestational age 25-31.5 weeks, n = 8), 141.0 +/- 14.2 fmol/ml in full term newborn babies (n = 5), 50.0 +/- 2.3 fmol/ml in children (age 1-6 years, n = 6), and 9.5 +/- 1.5 fmol/ml in 5 adults. The differences between successive age groups were all statistically significant. The high concentration of substance P in human CSF in the early stages of development and its continuous decline towards maturity encourages the idea that substance P plays a role in neuro-development.