In situ hybridization histochemistry with oxytocin synthetic oligonucleotide: strategy for making the probe and its application.

A 25 mer synthetic oligonucleotide, complementary to a specific region of the oxytocin-neurophysin preprohormone messenger RNA (mRNA), was designed for its application to in situ hybridization histochemistry. The probe was 3'-end labeled with [3H] deoxycytidine triphosphate (dCTP) by using terminal deoxynucleotidyl transferase, and hybridization of the labeled probe to the mRNA in the rat hypothalamus was visualized autoradiographically. Hybridization products were specifically localized in the dorsal part of the supraoptic nucleus and the peripheral part of the paraventricular nucleus. Not only is the oligomer designed useful for distinguishing oxytocin from vasopressin gene expressing neurons, but also it is proving useful for studies of estrogen-progesterone effects on neurons in the paraventricular nucleus. Thus, these results indicate that in situ hybridization histochemistry with synthetic oligonucleotide can be a valuable approach to measuring gene expression in hypothalamic neuroendocrine cells.