Immunocytochemical staining of supraoptic neurons from homozygous Brattleboro rats by use of antibodies against two domains of the mutated vasopressin precursor.

By use of antibody against the 14 amino acids in the mutated vasopressin precursor (CP-14) characteristic of the homozygous Brattleboro rat, an immunohisto- and -cytochemical study was performed on the supraoptic nuclei of homozygous Brattleboro rats. At the light-microscopic level, varying numbers of perikarya per section exhibited a positive reaction. The most intense staining was observed in a patchy manner on the peripheral portions of the cytoplasm, its central portion being stained less intensely. The antiserum did not react with the supraoptic perikarya of the Wistar rat. In the homozygous Brattleboro rat, antibodies against normal vasopressin only rarely resulted in a positive immunoreaction. However, when it was observed, incubation of the subsequent section with CP-14-antiserum suggested a co-localization of both peptides in the same perikaryon. At the ultrastructural level, CP-14 immunoreactivity was demonstrated on the secretory cisternae of the Golgi apparatus, on lysosome-like bodies and on parts of the rough endoplasmic reticulum. With the use of an antibody against normal vasopressin, immunoreactivity was confined to very limited areas of the rough endoplasmic reticulum. The oxytocin immunoreactivity in supraoptic perikarya of Brattleboro rats did not differ from that in the Wistar rat, either at the light- or at the electron-microscopic levels.