In vitro studies performed on cell lines or embryonic hypothalamic neuronal cultures suggest that neurotensin gene expression can be stimulated by dexamethasone, a synthetic glucocorticoid agonist. In order to test whether such an action could be observed in vivo, the distribution of neurotensin mRNA in the rat forebrain was analysed by in situ hybridization in rats treated chronically with corticosterone and in control animals. Corticosterone treatment resulted in a selective induction of neurotensin mRNA in both the periventricular and rostral arcuate nuclei of the hypothalamus but not in the paraventricular nucleus of the hypothalamus or the hippocampal CA1-CA2 region. This selective effect of corticosterone could be involved in neuroendocrine changes observed following glucocorticoid administration.