Orexin-A in the human brain and tumor tissues of ganglioneuroblastoma and neuroblastoma

Regional distribution of orexin-A-like immunoreactivity in the human brain and pituitary, and the presence of orexin-A-like immunoreactivity in the tu mor tissues of pheochromocytomas, ganglioneuroblastomas and neuroblastomas were studied by radioimmunoassay. Expression of orexin mRNA was studied by reverse transcriptase polymerase chain reaction (PCR) method. Orexin-A-like immunoreactivity was detected in every region of human brain, but not in t he pituitary. The highest concentration of orexin-A-like immunoreactivity i n the human brain was found in hypothalamus (17.8 +/- 4.3 pmol/g wet weight , mean +/- SEM, n = 7), followed by thalamus, medulla oblongata, and pens. Orexin-A-like immunoreactivity was detected in the tumor tissues of ganglio neuroblastoma and neuroblastoma, but not in the tumor tissues of pheochromo cytoma. Reverse phase high performance liquid chromatographic analyses of t he orexin-A-like immunoreactivity in the human brain extracts and neuroblas toma extracts showed a single immunoreactive peak, which was eluted in an i dentical position to synthetic human orexin-A, Orexin mRNA was expressed in the hypothalamus and in the tumor tissues of ganglioneuroblastoma and neur oblastoma. These findings suggest that orexin-A is produced in the hypothal amus and transported to various brain regions via axons. In addition, this study has shown for the first time the production of orexin-A by ganglioneu roblastomas and neuroblastomas. (C) 2000 Elsevier Science Inc. All rights r eserved.