DevelopmentalBrain Research, 32 (1987) 241-246 241 Elsevier BRD 50524 Human corticoliberin hypothalamic neuroglandular system: comparative immunocytochemical study with anti-rat and anti-ovine corticotropin-releasing factor sera in the early stages of development Jean-Luc Bresson, Marie-Claire Clavequin, Dominique Fellmann and Claude Bugnon Laboratory of Histology-Embryology, U.A. C.N.R.S. Facultyof Medicine and Pharmacy, Besanfon (France) (Accepted 9 September 1986) Key words: Corticoliberin neuron; Ovine corticotropin-releasing factor; Rat corticotropin-releasing factor; Human fetal hypothalamus; Development; Immunocytochemistry Development of the paraventriculo-infundibular corticoliberin system was studied by immunocytochemical analysis of human hy- pothalamic sections using antisera raised against rat or ovine corticotropin-releasing factor (CRF). This comparative study confirms the presence of a significant number of CRF-immunoreactive fibers in the median eminence during the 16th week of fetal devel- opment and suggests they may appear as early as the 14th week. Some hypothalamic peri- and paraventricular neurons, observed from the 12th week, are rat-CRF-immunoreactive but not ovine CRF-immunoreactive. There appears to be chronological differences con- cerning the ability of the two antisera to recognize hypothalamic structures during the early stage of development. INTRODUCTION Since 1982, our group has been studying the corti- coliberin neurons in the human hypothalamus by means of an antiserum raised against synthetic ovine corticotropin-releasing factor (oCRF) 15. This al- lowed us to give the first description of these neurons in the rat 5'6 and to study them in numerous vertebrate species, anatomically but also ontogenetically and morphophysiologically 1°. In man, we have analysed the paraventriculo-infundibular distribution of the oCRF immunoreactive neuroglandular system, the topographical relationships of its axonal projections with those of other peptide systems in the median eminence, the vasopressin-type immunoreaction ob- tained with some of its perikarya and, from the onto- genetic point of view, the appearance of the immuno- reaction to the anti-oCRF serum in the median emi- nence of the fetus at the 16th week in utero 1'4'7. The presence of CRF-immunoreactive fibers in the medi- an eminence at that time suggests previous differ- entiation of perikarya that we have not however been able to show at earlier stages. More recently, Daikoku et al. 9 used anti-oCRF and anti-rat CRF (rCRF) sera to demonstrate the existence of two types of rCRF-immunoreactive neu- rons in the adult rat: one, common in the paraventric- ular nucleus (PVN) that is oCRF-immunoreactive (oCRF+) but a-melanocyte-stimulating hormone non-immunoreactive (a-MSH-), the other, situated in the posterolateral hypothalamus that is oCRF- but a-MSH+ and identical to those previously dem- onstrated with a-MSH antiserum by other authors. They had also noticed that the anti-rCRF serum showed up perikarya in the rat at the gestational age of 15.5 days in the lateral hypothalamus and at 16.5 days in the PVN, this being two days earlier than had been achieved with their anti-oCRF serum, a fact they attributed to a better recognition of the rat CRF by their anti-rCRF serum 8. Correspondence: J.L. Bresson. Laboratoire d'Histologie-Embryologie, Facult6 de M6decine, 25030 Besanqon Cedex, France. 0165-3806/87/$03.50 © 1987 Elsevier Science Publishers B.V. (Biomedical Division)