- Birth-related up-regulation of mRNA encoding tyrosine hydroxylase, dopamine beta-hydroxylase, neuropeptide tyrosine, and prepro-enkephalin in rat adrenal medulla is dependent on postnatal oxygenation. Holgert, H., Pequignot, J.M., Lagercrantz, H., Hökfelt, T. Pediatr. Res. (1995)