ALTERATIONS IN KAPPA-OPIOID RECEPTOR MESSENGER-RNA LEVELS IN THE PARAVENTRICULAR NUCLEUS OF THE HYPOTHALAMUS BY STRESS AND SEX STEROIDS

IN this study, the levels of kappa opioid receptor (kOR) mRNA were det ermined using in situ hybridization following two types of stress (i.p . injection of hypertonic saline or novelty). In addition, we examined the possibility that estrogen or androgen would modify kOR mRNA. Gona dectomized male rats treated with estrogen or dihydrotestosterone were sacrificed 45 min after spending 15 min in a novel open field, or 60 min following hypertonic saline injection. Two-way ANOVA revealed that estrogen and novelty increased the levels of kOR mRNA in the ventral zone of the medial parvocellular part of the paraventricular nucleus ( PVN), but not in the lateral parvocellular part of the PVN, claustrum, nucleus accumbens or the nucleus of the lateral olfactory tract. Furt hermore, novelty increased kOR mRNA in gonadectomized (GDX) and GDX ra ts treated with dihydrotestosterone (DHTP), but not in sham-operated o r estrogen-treated animals. Taken together, these data indicate that k OR mRNA levels are under estrogenic control and up-regulated in a stre ssor specific fashion.