HETEROGENEITY IN CALBINDIN-D28K EXPRESSION IN OXYTOCIN-CONTAINING MAGNOCELLULAR NEURONS OF THE RAT HYPOTHALAMUS

We have used a double-labeling immunofluorescence method to examine wh ether oxytocin-containing magnocellular neurons possess a calcium-bind ing protein, calbindin-D28k, in the hypothalamus of the rat. In the su praoptic nucleus, most oxytocin-immunoreactive cells were also stained for calbindin-D28k. However, in the magnocellular part of the paraven tricular nucleus nearly all oxytocin-labeled cells were devoid of calb indin-D28k. In the anterior commissural nucleus, approximately one-thi rd of oxytocin-stained cells were also calbindin-D28k-immunoreactive, but the other cells were negative for calbindin-D28k. This study indic ates that there may be distinct chemical features between oxytocin-con taining magnocellular neurons of the supraoptic nucleus compared to th ose of the paraventricular nucleus.