Normative values of substance P and neurokinin A in neonates.
BACKGROUND
Substance P (SP) and neurokinin A (NKA) are neuropeptides that have been researched as pain markers in adults, as they are involved in transmission and modulation of pain signals. There is a potential role for them as neurochemical markers of pain in neonates, but this has never previously been investigated.


OBJECTIVE
To establish normative values of SP and NKA in neonates.


METHODS
Longitudinal once-daily morning blood samples were collected over two weeks from 142 neonates, gestation 23-40 weeks. Peptides were extracted, and then quantified using an in-house radioimmunoassay. Infants with presumed painful conditions were excluded.


RESULTS
SP concentrations ranged from <0.98 to 11.2 pmol/L (median 1.7 pmol/L) and NKA concentrations from <1.95 to 74.6 pmol/L (median 6.0 pmol/L). Gestation and birth weight had no significant correlation with peptide concentrations. Postnatally, there was a gradual rise in median SP during the first three days, which decreased again by day 14. Median NKA showed a similar rise, but was not statistically significant. This postnatal rise and fall were more apparent in preterm infants < or = 32 weeks gestation.


CONCLUSIONS
This is the first description of normative values of SP and NKA in neonates. SP and NKA show changes with postnatal age, which are more marked in preterm infants.
Wong
C Mae
CM
Neonatal Unit, Simpson Centre for Reproductive Health, Edinburgh EH16 4SA, UK. chuimae@yahoo.co.uk
Boyle
Elaine M
EM
Stephen
Rhona I
RI
Smith
John
J
Stenson
Benjamin J
BJ
McIntosh
Neil
N
Laing
Ian A
IA
D000367:Age Factors; D015415:Biomarkers / Q000097:blood; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D015288:Neurokinin A / Q000097:blood / Q000592:standards*; D010146:Pain / Q000097:blood; D011247:Pregnancy; D047928:Premature Birth / Q000097:blood; D012016:Reference Values; D013373:Substance P / Q000097:blood / Q000592:standards*
D015415:Biomarkers; D013373:Substance P; D015288:Neurokinin A