Neonatal development of ACTH-immunoreactive neurons in the rat

Using immunohistochemical techniques, the distribution of ACTH 25-39 immunoreactive perikarya and fibers was studied in the newborn rat. Perikarya and fibers were demonstrated on day 1 after birth in the diencephalon, mesencephalon, pons and medulla. However, the amount of material increased rapidly from the first to third day of postnatal development.