Neuroendocrine studies on modulation of the function of the hypothalmo-pituitary-gonadal axis with nutrients

据报道，哺乳刺激是抑制哺乳期黄体生成素分泌的主要因素。哺乳刺激会随着哺乳时间的推移或母鼠的生理状况（如产仔数、发育程度）而发生变化。我们首先研究了电刺激乳腺神经是否可以代替哺乳刺激，其次，我们研究了哺乳刺激对去卵巢泌乳大鼠整个泌乳期lh分泌模式的影响。电刺激乳腺神经和隐神经、正中神经均可使血浆催产素浓度升高。虽然氯丙嗪能够抑制固定应激下血浆催产素水平的升高，但氯丙嗪不能阻止电刺激乳腺、隐神经和正中神经后血浆催产素水平的升高。没有增加，血浆催产素水平增加当母鼠和封口不吮吸乳汁的幼崽放在一起时。需要进一步的研究来区分催产素对电刺激乳腺神经的反应与对正中神经和隐神经的反应。完整大鼠在哺乳期第10天和第20天脉动性LH分泌被强烈抑制，血浆LH基线保持在很低水平。在去卵巢的大鼠中，基线保持在与完整大鼠相同的水平，在第10天，第20天，基线升高，6只去卵巢的哺乳大鼠中有5只出现搏动分泌。在第6天和第15天，注射雌二醇的哺乳期大鼠在下午晚些时候出现每日LH激增。泌乳第8天取崽后，平均LH水平及LH脉冲频率和振幅逐渐升高。在周期大鼠卵巢切除术后，黄体生成素脉冲频率不变，但平均黄体生成素水平和黄体生成素脉冲幅度增加。这些结果清楚地表明：1。哺乳刺激在下丘脑-垂体水平抑制脉动性黄体生成素分泌的作用在哺乳后期被消除。2. 雌二醇诱导黄体生成素激增的机制不受哺乳刺激的损害。3. 哺乳刺激抑制搏动分泌的方式与卵巢类固醇不同。少

The suckling stimulus has been reported to be a dominant factor suppressing LH secretion during lactation. The suckling stimulus could change with the advancement of lactation or physiologcal condition of mothers e.g. number of pups the degree of pups development. We, first, studied whether or not the electrical stimulation of the mammary nerve could be used as a substitute for the suckling sitmulus, and secondly, we studied effects of thesuckling sitmulus on the secretory pattern of lh in ovariectomized lactating rats throughout the lactating peruid.1. The electrical sitmulation of not only the mammary nerve but also the saphoenous and median nerves increased the plasme oxytocin concentration. Although chlorpromazine adminidtration was able to inhibit the increase of plasma oxytocin level in response to the immobilization stress, chlorpromazine administration failed to prevent the increase occurring after the electrical stimulation of the mammary, saphenous and median nerves. No incre … More ase in the plasma oxytocin levels when the mother was placed with pups whose mouths were sealed not to suckle the teat. Further studies are required to discriminate the oxytocin response to the electrical stimulation of the mammary nerve from that to the sitmulation of the median and saphenous nerves.2. Pulsatile LH secretion was strongly suppressed on either day 10 or 20 of lactation in intact rats in which the base line of plasma LH was kept very low. In ovariectomized rats the base line was kept as low as that observed in intact rats on day 10 day 20 the base line raised and pulsatile secretion appeared in 5 out of 6 ovraiectomized lactating rats. Daily LH surges occurred in the late afternoon in both lactating rats inplanted with estradiol on day 6 or 15. The mean LH level and the frequency and amplitude of LH pulses gradually increased after removal of pups on day 8 of lactation. In cycling rats the frequency of LH pulses was unchanged after ovariectomy, although the mean LH level and the amplitude of LH pulses increased. These results clearly indicate: 1. Suppression of pulsatile LH secretion by the suckling stimulus at the hypothalamo-pituitary level is removed in late lactation. 2. The mechanisms responsible for the estradiol induced LH surge are not impaired by the sucklig sitmulus. 3. The suckling sitmulus suppresses pulsatile secretion in a different manner from that of ovarian steroids. Less