Postnatal developmental changes in NSE and NNE mRNA expression in the rat pineal gland: in situ hybridization histochemistry.

By in situ hybridization, neuron-specific enolase (NSE) and non-neuronal enolase (NNE) mRNAs were examined in the rat pineal gland at the postnatal developmental and adult stages. The distributions of hybridized signals were analyzed in comparison with immunohistochemical staining of synaptophysin (SYN), which is a marker for pinealocytes. In SYN-positive areas that were observed throughout postnatal developmental and adult stages, we detected both NSE and NNE signals, which increased simultaneously during early postnatal development and thereafter became stationary. Quantitative analysis revealed that NNE signals were 2- to 3-fold greater in number than NSE signals at any given stage. This predominant expression pattern of NNE differed from that in neurons, which usually showed both signals at similar levels and seemed to reflect the difference in physiological function from neurons. During the early postnatal stages, a cord-like arrangement of cells without distinct SYN staining was observed. This arrangement was the thickest at postnatal day 0 and became dispersed and thinner with development, showing a relationship with formation of vascularized connective tissue stroma. By in situ hybridization, many of the constituent cells showed weak NNE signals but no distinct NSE signals. However, some cells also showed weak NSE signals, suggesting heterogeneity of these cells. The characteristic NSE and NNE expression patterns in the pineal gland cells clarified in this study might provide a basis for further studies of the differentiation and function of the pineal gland.