Animals, Humans, Rats, Animals, Newborn, Female, Aging, In Vitro Techniques, Pregnancy, Body Weight, Epinephrine, Morphine, Catecholamines, Adrenal Medulla, Dopamine beta-Hydroxylase, Maternal-Fetal Exchange, Metaraminol, Morphine Dependence, Tyrosine 3-Monooxygenase