Opposite effects of short and continuous oestradiol replacement on CNS responses to hypoxic stress

Oestrogen can alter neuroendocrine responses to stress but the evidence is conflicting. We examined the effects of a shortterm 17 beta-oestradiol surg e versus a continuous 17 beta-oestradiol replacement regime on neuroendocri ne cell responses to hypoxia in the ovariectomized rat. Short-term oestradi ol replacement significantly increased the number of Fos-positive SON and P VN OT cells and VLM Al and CI cells following hypoxia. In contrast, continu ous oestradiol replacement significantly decreased the number of hypoxia-in duced Fos-positive mPVN, PVN OT and VLM Al and CI and NTS C2 cells. We prop ose that the effects of oestradiol replacement on stress-induced neuroendoc rine responses may be dependent on whether oestrogen levels are rising rapi dly or remaining constant over a relatively long period. NeuroReport 11:224 3-2246 (C) 2000 Lippincott Williams & Wilkins.