Colocalization of calbindin-D28k with vasopressin in hypothalamic cells of the rat: a double-labeling immunofluorescence study.

By use of a double-labeling immunofluorescence method, we examined whether vasopressin-containing cells possess a calcium-binding protein, calbindin-D28k, in the hypothalamus of the rat. Subpopulations of vasopressin-containing cells varied in their ability to possess calbindin-D28k immunoreactivity in different regions. In the supraoptic nucleus, most vasopressin-immunoreactive cells were also stained for calbindin-D28k. By contrast, in the magnocellular part of the hypothalamic paraventricular nucleus, all vasopressin-labeled cells lacked calbindin-D28k. In the suprachiasmatic nucleus, no calbindin-D28k was found in vasopressin-stained cells. This study shows a further characterization of vasopressin-containing cells of the rat hypothalamus.