ESTROGEN ALTERS PROENKEPHALIN RNAS IN THE PARAVENTRICULAR NUCLEUS OF THE HYPOTHALAMUS FOLLOWING STRESS

Gonadal steroids modulate activity of the hypothalamo-pituitary-adrena l axis (HPA) following stress, but the regulatory pathways of this mod ulation are unknown. A possible site of action is the synthesis of CRH and/or enkephalin in cells of the paraventricular nucleus of the hypo thalamus (PVN). To investigate this possibility, we utilized two stres sors, i.p. hypertonic saline injection (HSI) or exposure to novel envi ronment, and examined the response of CRH or c-fos mRNAs and proenkeph alin (PPE) mRNA and heteronuclear RNA (hnRNA, primary transcript). Mal e rats were gonadectomized and treated with estrogen or dihydrotestost erone propionate (DHTP) for 2 weeks. In situ hybridization revealed th at novelty or HSI elevated levels of PPE hnRNA and c-fos mRNA in the P VN. Estrogen attenuated the elevation of PPE hnRNA in the PVN followin g HSI, and enhanced the c-fos mRNA response to novelty. In contrast, D HTP did not affect PPE hnRNA, but inhibited the c-fos mRNA response to novelty. These data indicate that in male rats estrogen receptor but not androgen receptor may modulate the endocrine stress response by al tering PPE transcription in the PVN and that this effect depends on th e type of stressor. (C) 1997 Elsevier Science B.V.