Ontogeny of the Neuroglandular System Revealed with HPGRF 44 Antibodies in Human Hypothalamus

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Abstract
Using the indirect immunofluorescence technique, an antiserum to synthetic hpGRF 44 (the 44 residue peptide with high growth hormone releasing activity isolated from a human pancreatic tumor), antibodies of which interact with 40–44 C terminal amino acid sequence, stains a novel neuron system in the adult human hypothalamus. HpGRF-like immunoreactivity (GLI) containing neurons are different from previously known peptidergic systems. GLI perikarya are few in number and located mainly in the infundibular nucleus. In the median eminence, abundant GLI fibers terminate against portal capillaries in the same areas as somatostatin fibers which are morphologically different. No GLI staining was observed in hypothalami before 18 weeks of fetal development. GLI perikarya and intraeminential nerve terminals were simultaneously detected in 18-week-old fetuses attesting to a possible release of this peptide in the portal vessels as early as this stage. GLI neuron system was steadily revealed in 19- to 30-week-old fetuses. It was not detectable in 6 out of the 7 studied hypothalami from newborn infants. In most infant and adult hypothalami, it is well developed. Results presented here support the hypothesis (1) that hpGRF antiserum stains the neuron system producing the somatocrinin and (2) that this neuron system may begin in controlling pituitary somatotrophs at the 18th week of fetal development, which is in agreement with previous hypotheses.