Neurochemical Identification of Hypothalamic Neurons Expressing c-Fos in response to Hypertonic Saline / 대한해부학회지

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.

Effect of adenylate cyclase inhibitor and protein kinase C inhibitor on GnRH-induced LH release and LH beta subunit biosynthesis in rat anterior pituitary cells

According to our previous studies together with others, GnRH, a hypothalamic decapeptide, has been known to be a major regulator for LH release and its subunit biosynthesis in anterior pituitary gonadotropes. But the precise mechanisms by which GnRH exerts stimulatory effects on LH release and its subunit biosynthesis have not been clearly understood. In the present study we examined the effect of GnRH on protein kinase C (PKC) activity and intracellular cAMP content in cultured anterior pituitary cells of rat to clarify whether PKC or cAMP are involved in GnRH action. Moreover, we examined the effects of staurosporine (ST), a PKC inhibitor and 2',3'-dideoxyadenosine (2',3'-DDA), an adenylate cyclase inhibitor, on LH release and steady state LH beta subunit mRNA levels in cultured anterior pituitary cells of rat. PKC activity was rapidly increased within 30 min after GnRH treatment whereas intracellular cAMP level was elevated 18 h after GnRH treatment. ST significantly inhibited GnRH-induced LH release and LH beta subunit mRNA levels in a dose-dependent manner, showing an half maximal response at 50 nM ST. 2',3'-DDA inhibited GnRH-induced LH release and LH beta subunit mRNA levels in a dose-dependent manner in pituitary cells. From these results, it is suggested that GnRH stimulates LH beta subunit mRNA level as well as LH release in anterior pituitary cells and this GnRH action might be mediated by PKC activation and cAMP stimulation.