[Detection of mRNA in electronic microscopy: in situ hybridization of a biotin-labeled oligonucleotide prior to embedding].

A technique for mRNA detection by ultrastructural in situ hybridization is reported. Vibratome sections are hybridized with a biotinylated oligonucleotide probe which is detected using an enhanced avidin-peroxidase technique. Sections are then osmicated and embedded in epoxy resin. This rapid, sensitive technique achieved ultrastructural detection of vasopressin mRNA in magnocellular neurons of rat hypothalamus.