In situ hybridization of oxytocin messenger RNA: macroscopic distribution and quantitation in rat hypothalamic cell groups.

Oxytocin mRNA was detected in the rat hypothalamus by in situ hybridization to a single stranded 35S-labelled DNA probe and the distribution of oxytocin mRNA-containing cell groups was studied at the macroscopic level. Specificity of hybridization was confirmed by comparison to vasopressin mRNA hybridization in parallel tissue sections. Cell groups containing oxytocin mRNA were confined to a set of hypothalamic cell groups, i.c. the supraoptic, paraventricular, anterior commissural nuclei, nucleus circularis and scattered hypothalamic islets. These cell groups displayed similar densities of autoradiographic signals indicating that the oxytocin gene is expressed at approximately the same average level at these various sites.