Eicosanoids in third 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.(ABSTRACT TRUNCATED AT 250 WORDS)