Résumé
Previous studies have shown that hypertonic saline induces c-fos expression in the magnocellular neurons of rat hypothalamus. The present immunohistochemical double-labeling study was undertaken to determine the identification of magnocellular neurons expressing c-Fos in response to osmotic stimulus. Hypertonic saline induced c-Fos-like immunoreactivity (FLI) in various regions of hypothalamus in addition to supraoptic nucleus (SON) and paraventricular nucleus (PVN). FLI was detected in most of oxytocin neurons in the preoptic region and in the accessory nuclei located between the PVN and SON as well as in the SON and PVN. In particular, most of all oxytocin neurons in the accessory nuclei were labeled for c-Fos. There were also many FLI cells that did not show oxytocin and vasopressin immunore-acitivity in their cytoplasm. Relative frequencies of oxytocin and vasopressin neuronal responses showed that much more cells of oxytocin than vasopressin were induced to express c-fos in response to hypertonic saline. These data show that both oxytocin and vasopressin neurons are sensitive to osmotic stimulus and activated via expression of c-Fos by hypertonic saline.