Smith F G, Fewell J E, Abu-Amarah I
Department of Physiology and Biophysics, University of Calgary, Alberta, Canada.
Am J Physiol. 1997 Sep;273(3 Pt 2):R1053-7. doi: 10.1152/ajpregu.1997.273.3.R1053.
In adult rats, exposure to a novel environment, such as a simulated open field, elicits an increase in body core temperature. We have recently shown that this response is attenuated in midpregnancy and abolished at term of pregnancy in rats. We postulated that this gestation-dependent response resulted from alterations in the hypothalamic-pituitary-adrenal axis. To test this hypothesis, we measured the effects of pregnancy on renin, corticosterone, and arginine vasopressin (AVP) responses to exposure to either a simulated open field (30 or 120 min) or to the home cage (30 or 120 min) in rats. Pregnancy increased renin and corticosterone levels but not plasma AVP levels. Exposure to an open field decreased renin and increased plasma AVP levels in nonpregnant rats and on days 15 and 20 of gestation in pregnant rats, compared with home cage responses. Serum corticosterone levels were elevated after exposure to an open field in nonpregnant and pregnant rats, compared with home cage rats, the effect being more prolonged on day 20 of gestation. These observations provide new information on endocrine changes during pregnancy in rats and may help to explain the attenuated stress-induced hyperthermic response to exposure to a novel environment seen near term of pregnancy.
在成年大鼠中，暴露于新环境，如模拟的旷场，会引起体核温度升高。我们最近发现，这种反应在大鼠妊娠中期减弱，在妊娠末期消失。我们推测这种依赖于妊娠的反应是由下丘脑-垂体-肾上腺轴的改变引起的。为了验证这一假设，我们测量了妊娠对大鼠暴露于模拟旷场（30或120分钟）或饲养笼（30或120分钟）时肾素、皮质酮和精氨酸加压素（AVP）反应的影响。妊娠增加了肾素和皮质酮水平，但未增加血浆AVP水平。与饲养笼对照相比，暴露于旷场使未孕大鼠以及妊娠第15天和第20天的孕鼠肾素水平降低，血浆AVP水平升高。与饲养笼中的大鼠相比，未孕和孕鼠暴露于旷场后血清皮质酮水平升高，在妊娠第20天这种效应持续时间更长。这些观察结果为大鼠妊娠期间的内分泌变化提供了新信息，可能有助于解释妊娠末期暴露于新环境时应激诱导的体温过高反应减弱的现象。
