Localization of neuroendocrine secretory protein 55 messenger RNA in the rat brain

Neuroendocrine secretory protein 55 (NESP55) is a recently characterized se cretory protein localized to large dense-core vesicles resembling the class of chromogranins. We investigated the distribution of the messenger RNA en coding for NESP55 in the rat brain by in situ hybridization with specific S -35-labelled oligonucleotides. NESP55 messenger RNA was detected only on ne uronal but nor glial cells. In the brain, expression of NESP55 messenger RN A was most prominent in several areas throughout the midbrain and brainstem , including the locus coeruleus, the raphe complex and the reticular format ion. NESP55 messenger RNA-expressing cells were also found in many areas an d nuclei throughout the hypothalamus. Neocortical areas, the hippocampus an d the cerebellum were devoid of NESP55 messenger RNA-containing neurons. Fr om this distribution pattern, a significant overlap of NESP55 expression wi th the noradrenergic, adrenergic and serotonergic transmitter systems was e vident. The present study defines, for the first rime, the cellular localizaton of NESP55 messenger RNA in the rat brain. The present results provide the basi s for future studies defining the as yet obscure function of NESP55, (C) 19 99 IBRO. Published by Elsevier Science Ltd.