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 tumor 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 the pituitary. The highest concentration of orexin-A-like immunoreactivity in 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 pons. Orexin-A-like immunoreactivity was detected in the tumor tissues of ganglioneuroblastoma and neuroblastoma, but not in the tumor tissues of pheochromocytoma. Reverse phase high performance liquid chromatographic analyses of the orexin-A-like immunoreactivity in the human brain extracts and neuroblastoma extracts showed a single immunoreactive peak, which was eluted in an identical position to synthetic human orexin-A. Orexin mRNA was expressed in the hypothalamus and in the tumor tissues of ganglioneuroblastoma and neuroblastoma. These findings suggest that orexin-A is produced in the hypothalamus and transported to various brain regions via axons. In addition, this study has shown for the first time the production of orexin-A by ganglioneuroblastomas and neuroblastomas.