PRENATAL AND POSTNATAL EFFECTS OF CHRONIC MATERNAL HYPOXIA ON SUBSTANCE-P IMMUNOREACTIVITY IN RABBIT BRAIN-STEM REGIONS

The effect of chronic maternal hypoxia on substance-P immunoreactivity (SPI) was examined in brainstem regions of fetal (gestational day E-2 8), neonatal (postnatal days 3, 7, 14, 21), and adult rabbits. Time-da ted pregnant rabbit does were housed in environmental chambers at gest ational day E-10. Between E-14 and E-28, the pregnant does were separa ted into two groups, Group 1, the control group, breathed 21% O-2/79% N-2 and group 2 the hypoxia-exposed group, breathed 12-14% O-2/86-88% N-2. Sacrifice occurred at various days depending on the experimental paradigm. On gestational day E-28, 6 pregnant animals were delivered b y hysterotomy and the pups were immediately sacrificed. On and after g estational day E-28, the remaining 12 pregnant animals breathed room a ir. These animals delivered spontaneously between E-30 and E-32 and th e pups remained with their mothers until sacrifice. On postnatal days 3, 7, 14, and 21, SPI was measured by radioimmunoassay in the collicul i (fetal animals), superior and inferior colliculi (postnatal animals) , pens and medulla (both groups). In both prenatally normoxia- and hyp oxia-exposed animals, SPI was highest in the medulla, intermediate in the pens and lowest in the colliculi, SPI increased with development. Chronic maternal hypoxia did not alter the caudal-rostral profile nor did it alter the maturational increase in SPI. However, chronic matern al hypoxia increased SPI in prenatal animals and decreased SPI in post natal animals at 14 and 21 days of life but not in postnatal 3- or 7-d ay-old animals. These data support the concept that regional differenc es exist in basal SPI within the brainstem of fetal and neonatal anima ls, and that maternal hypoxia has both immediate and long-term effects on brainstem SPI.