Calbindin D28k and calretinin in oxytocin and vasopressin neurons of the rat supraoptic nucleus - A triple-labeling immunofluorescence study

The aim of the present study was to examine quantitatively whether two calc ium-binding proteins, calbindin D28k and calretinin, are localized in oxyto cin and vasopressin neurons of the supraoptic nucleus of the male rat. We u sed a triple-labeling immunofluorescence method with a confocal laser scann ing microscope. Of the oxytocin-labeled cells, 70% were stained for both ca lbindin D28k and calretinin, 15% were stained for only calbindin D28k, 13% were stained for only calretinin, and 2% were stained for neither protein. Of the vasopressin-labeled cells, 73% were stained for neither calbindin D2 8k nor calretinin, 21% were stained for only calbindin D28k, 4% were staine d for only calretinin, and 2% were stained for both proteins. Calbindin D28 k and calretinin :have been shown previously to contribute to calcium homeo stasis by buffering [Ca2+](i). Therefore, these findings suggest that most of the oxytocin neurons may have a higher Ca2+-buffering capacity than most of the vasopressin neurons.