Postnatal ontogeny of POMC gene expression in the rat pituitary: an analysis by in situ hybridization histochemistry

Postnatal development of proopiomelanocortin gene expression in the rat pituitary was examined using in situ hybridization histochemistry. In adult rats, a very high density of hybridization signals was seen in the intermediate lobe of the pituitary, while only a moderate density occurred in the anterior lobe. No evidence of hybridization was detected in the posterior lobe. At birth, both the intermediate and anterior lobes had low to moderate frequencies of hybridization signals but a rapid rise to moderate density was noted by the 8th postnatal day. Radioactive labelling in the intermediate lobe continued to increase sharply with age to reach a plateau at postnatal day 28, while hybridization signals in the anterior lobe levelled off at postnatal day 8 with no subsequent rise in density.