Norepinephrine in fetal and neonatal rabbit brain.

In the first hour after parturition, the newborn rabbit brain norepinephrine content is about 37% less than that of the fetus of 30th or 31st day. Later on, within 2 to 4 h, the norepinephrine level returns to the prenatal value and remains unchanged between 8 to 12 h. This transitory fall of the brain norepinephrine seems to be linked to the stress conditions which occur during parturition.