Effects of dexamethasone and forskolin on neurotensin production in rat hypothalamic cultures.

In the present study, the effects of glucocorticoids and forskolin, an activator of adenylate cyclase, were examined on neurotensin (NT) production from rat hypothalamic neurons in primary culture. Treatment with dexamethasone induced a dose-dependent increase in NT content. The maximum was reached at 1 microM dexamethasone, which induced a 100% increase in NT levels. The effect of dexamethasone was mimicked by the glucocorticoid agonist RU28362 and blocked by the antiglucocorticoid RU38486, suggesting that this effect was mediated through the glucocorticoid receptor. The treatment with dexamethasone also enhanced the number of immunoreactive NTergic cells (92% increase). In contrast to dexamethasone, forskolin affected neither the NT content nor the number of immunoreactive NTergic cells. However, when cells were treated with both dexamethasone and forskolin, a 285% increase in NT content and a 430% increase in the number of immunoreactive NTergic cells were observed, representing 2.8- and 4.7-fold increases, respectively, compared to the effect of dexamethasone alone. Moreover, this combined treatment increased the accumulation of NT in the culture medium (160% increase) as well as the abundance of NT messenger RNA. We conclude from the present findings that dexamethasone and forskolin act synergistically to enhance NT production in hypothalamic neurons.