LOCALIZATION OF CORTICOTROPIN-RELEASING FACTOR IMMUNOREACTIVITY IN THE BRAIN OF THE TELEOST SPARUS-AURATA

The distribution of perikarya and fibers containing corticotropin-rele asing factor (CRF) was studied in the brain of the teleost Sparus aura ta by immunocytochemistry using the peroxidase-antiperoxidase method. Antisera against rat CRF, arginine vasotocin, and human adrenocorticot ropin (ACTH) were used. Most CRF-im munoreactive neurons were located in the nucleus lateralis tuberis, but they were absent from the nucleu s preopticus, which only contained arginine vasotocin neurons. Few CRF perikarya were identified in the nucleus preopticus periventricularis and in the mesencephalic tegmentum. A conspicuous bundle of immunorea ctive fibers ran along the diencephalic floor and pituitary stalk to e nd near the cells of the hypophysial pars intermedia. No CRF was seen near the adenohypophysial rostral pars distalis. Our results suggest t hat, in Sparus aurata, CRF is a releasing factor for melanotropic cell s. Its role as a releasing factor for ACTH is discussed.