EICOSANOIDS IN 3RD VENTRICULAR CEREBROSPINAL-FLUID OF FETAL AND NEWBORN SHEEP

A method to serially sample cerebrospinal fluid (CSF) from the third ventricle of chronically catheterized fetal and newborn sheep was developed. Either sampling cannulas of preset lengths (''fixed-probe' technique) or a single cannula that could be positioned at the desired depth (''roving-probe'' technique) was used. The roving probe proved superior because free CSF flow was obtained in seven of ten animals after surgery compared with two of nine animals implanted with a fixed probe. CSF (5 animals) and plasma (7 animals) was collected serially from 2 wk before to 2 wk after birth, including the time around labor. Prostaglandin E2 (PGE2) levels (means +/- SE) were significantly higher in CSF (366 +/- 120 pg/ml; n = 5) and plasma (520 +/- 69 pg/ml; n = 7) before the day of delivery than in the same animals after birth. During labor, CSF and plasma PGE2 levels increased significantly to 1,428 +/- 643 pg/ml in CSF and to 2,015 +/- 414 pg/ml in plasma. However, by 1 h after birth, PGE2 had fallen to 366 +/- 165 pg/ml in CSF and to 338 +/- 106 pg/ml in plasma; levels similar to those observed in the fetus before labor. PGE2 continued to decrease precipitously and, at 24 h of age, levels were significantly less than those observed in the fetus. PGE2 levels were near the limit of detection of the assay in CSF (<5 pg/ml) and were 49 +/- 10 pg/ml in plasma. In contrast, CSF thromboxane B2 (n = 2) and total peptidoleukotriene content (n = 4) showed little change during labor or after birth. We conclude that specific changes in CSF and plasma PGE2 levels; occur in the perinatal period. Whether PGE2 in CSF is produced locally or is derived from peripheral sources and the role of these changes in adaptations to postnatal life remain to be determined.