Comparative immunoelectron microscopic localization of corticotropin-releasing factor (CRF-41) and oxytocin in the rat median eminence.

Comparative ultrastructural localization of corticotropin-releasing factor (CRF) and oxytocin was performed in the rat median eminence of Long Evans and Brattleboro rats. The peroxidase-antiperoxidase technique used on serial ultrathin sections revealed CRF and oxytocin neurosecretory granule colocalization in the same fibers of the internal layer running towards the posterior pituitary. It is probable that both these peptides coexist in the same granules. In the Brattleboro rats, while genetically lacking vasopressin, CRF was nevertheless shown to be present. In these rats, as was demonstrated in the Long Evans rats, CRF distribution paralleled that of oxytocin only in the internal zone of the median eminence.