Jorgenson K L, Schwartz N B
Neuroendocrinology. 1984 Dec;39(6):549-54. doi: 10.1159/000124036.
The purpose of these experiments was to determine whether daily gonadotropin surges that occur in intact or ovariectomized hamsters kept in short days (less than 12 h of light/day) are manifest because of extremely low levels of steroids. Hamsters were ovariectomized and placed in 16L:8D or 10L:14D. After 10-13 weeks, animals in each photoperiod were divided among four treatment groups: estradiol implant plus progesterone injection 5 days later; estradiol implant plus water injection; empty implant plus progesterone injection; empty implant plus water injection. Blood samples were taken from animals in the morning and afternoon before and after various treatments. In animals not receiving estradiol, all short-day and some long-day females showed low morning values of LH and surge values in the afternoon. Estrogen suppressed morning and enhanced afternoon values of LH in long-day animals, intensifying the surge. However, in the presence of estrogen, these LH surges eventually diminished in both photoperiods. Progesterone hastened the loss of the LH surge. Hamsters did not consistently demonstrate FSH surges until treated with estrogen. Serum FSH in untreated hamsters was much higher in long-day than in short-day animals. Treatment with both steroids maximally suppressed morning and afternoon FSH levels in all hamsters. Thus, in the absence of estrogen, circadian expression of LH surges always occurs in short days; FSH surges sometimes occur. In all animals showing spontaneous or estrogen-induced surges, estrogen eventually leads to inhibition of gonadotropin secretion, particularly in the presence of progesterone.(ABSTRACT TRUNCATED AT 250 WORDS)
这些实验的目的是确定，在短日照（光照时间每天少于12小时）条件下饲养的完整或去卵巢仓鼠中，每日出现的促性腺激素激增是否是由于类固醇水平极低所致。仓鼠被去卵巢后，分别置于16小时光照：8小时黑暗或10小时光照：14小时黑暗的环境中。10 - 13周后，每个光周期的动物被分为四个处理组：植入雌二醇并在5天后注射孕酮；植入雌二醇并注射水；植入空载体并注射孕酮；植入空载体并注射水。在各种处理前后，于上午和下午采集动物的血样。在未接受雌二醇的动物中，所有短日照和一些长日照雌性动物的促黄体生成素（LH）上午值较低，下午出现激增。雌激素抑制长日照动物LH的上午值并提高其下午值，增强了激增。然而，在有雌激素存在的情况下，这两种光周期中的LH激增最终都减弱了。孕酮加速了LH激增的消失。仓鼠在接受雌激素治疗之前，促卵泡生成素（FSH）激增并不一致。未处理的仓鼠中，长日照动物的血清FSH水平远高于短日照动物。两种类固醇同时处理能最大程度地抑制所有仓鼠上午和下午的FSH水平。因此，在没有雌激素的情况下，短日照时LH激增的昼夜节律性表达总是会出现；FSH激增有时会出现。在所有表现出自发性或雌激素诱导的激增的动物中，雌激素最终会导致促性腺激素分泌受到抑制，尤其是在有孕酮存在的情况下。（摘要截选至250词）
