Netherlands Central Institute for Brain Research, Ijdijk 28, Amsterdam – 0, The Netherlands
(Received 6 November 1974)
Although immunohistochemistry is considered to provide a specific and sensitive tool for the localization of hypothalamic hormones (Zimmerman, Hsu, Ferin & Koslowski, 1974), attempts to localize vasopressin and oxytocin by immunofluorescence have raised questions about the specificity of this technique. Homozygous Brattleboro rats were used in our experiments as a control for vasopressin immunofluorescence since their hypothalamo-neurohypophysial system (HNS) does not contain any measurable amount of this hormone (Valtin, Sawyer & Sokol, 1965). Despite this, bright fluorescence was observed in the HNS of these animals, not only using antibodies against oxytocin, but also with all tested antibodies raised against lysine- or arginine-vasopressin. In addition, immunofluorescence was observed beyond the HNS of Wistar and heterozygous Brattleboro rats, i.e. in the suprachiasmatic nucleus.
Because of these findings and the fact that the commonly used