DEVELOPMENTAL PROFILE OF CORTICOTROPIN-RELEASING HORMONE MESSENGER-RNA IN THE RAT INFERIOR OLIVE

Corticotropin releasing hormone is a neurotransmitter in the inferior olive complex of marsupials and mammals. The ontogeny of corticotropin releasing hormone gene expression in the rat inferior olive has not b een described. Using in-situ hybridization histochemistry in 25 animal s, we established the developmental profile of the peptide's messenger ribonucleic acid in the postnatal rat. CRH-messenger RNA was first de tectable in two of four animals on the fifth postnatal day. Subsequent ly, gene expression increased linearly with age: by day 14, CRH was ex pressed in all olivary complex nuclei, and the distribution and relati ve abundance on day 18 were comparable to those in the adult. The deve lopmental profile of CRH-mRNA in the rat interior olive differs from t hose in the mouse and opossum. and from the pattern in the rat hypotha lamus, suggesting species and site-specificity of the peptide's functi on.