Expression of vasopressin and opiates but not of oxytocin genes studied by in situ hybridization in embryonic rat brain primary cultures

Abstract

Expression of arginine-vasopressin (AVP), oxytocin (OT), dynorphin and enkephalin genes was studied with the in situ hybridization technique in embryonic rat brain serum-free cultures. Neurones were prepared from hypothalamus and extrahypothalamic structures of 16-day-old rat embryos. After 7 days in culture, AVP gene expression occurred in hypothalamic cultures only, whereas ProOT mRNAs were undetectable. By contrast, prodynorphin and proenkephalin mRNAs could be detected in both hypothalamic and extrahypothalamic cultures, however, with a higher number of cells containing proenkephalin mRNAs. These observations demonstrated that AVP, dynorphin and enkephalin, but not OT genes, can be expressed in cultures prepared from embryonic rat brain as young as 16 days old. This is the first report of an early expression of opioid peptide genes within the central nervous system suggesting that opioids could be involved in the early phases of nervous system development.