Gonadotropin-releasing hormone secretion into third ventricle cerebrospinal fluid of cattle: Correspondence with the tonic and surge release of luteinizing hormone and its tonic inhibition by suckling and neuropeptide Y
Gonadotropin-releasing hormone secretion into third ventricle cerebrospinal fluid of cattle: Correspondence with the tonic and surge release of luteinizing hormone and its tonic inhibition by suckling and neuropeptide Y
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DOI：
10.1095/biolreprod59.3.676
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发表时间：
1998-09-01
影响因子：
3.6
通讯作者：
Williams, GL
中科院分区：
文献类型：
--
作者：
Gazal, OS;Leshin, LS;Williams, GL
当前研究的目的是表征牛第三脑室脑脊液中GnRH的分泌模式，确定其与去卵巢奶牛LH的强补性和激增性释放的对应关系，并检查GnRH脉冲发生器活性对已知LH释放调节剂（哺乳；神经肽Y [NPY]）的响应动态。在去卵巢奶牛中，强亢释放模式与雌二醇诱导的GnRH和LH升高高度相关（0.95;p < 0.01）。总的来说，基线处的LH脉冲开始与GnRH脉冲（84%）或在GnRH脉冲（100%）开始后的一个采样点一致，所有雌二醇诱导的LH激增都伴随着相应的GnRH激增。500 μ g剂量的NPY可立即停止LH脉冲，降低血浆LH浓度至少4小时（p < 0.001）。这与GnRH脉冲幅度和频率的下降（p < 0.05）相对应，但GnRH脉冲仅在1.5-3小时内被完全抑制。在完整的无情奶牛中，GnRH脉冲频率在产后第18天断奶前和断奶后48-54小时没有差异。但GnRH浓度（p < 0.05）和GnRH脉冲振幅（4 / 7）随断奶和LH分泌增加而升高。我们认为，研究第三脑室CSF中GnRH的分泌动态为研究成年牛下丘脑脉冲发生器的活性和调节提供了一个合理的方法。但是，使用这种方法生成的数据必须在最广泛的上下文中进行解释。虽然强神经介导的LH脉冲抑制剂（哺乳；NPY）对CSF中的一种或多种GnRH分泌特征有强大的影响，但只有高剂量的NPY才能短暂地消除GnRH脉冲。这意味着在这些条件下垂体门静脉接收到的GnRH信号可能在数量或质量上与CSF中的GnRH信号不同，并且在理论上，当LH脉冲不存在时，GnRH信号将无法检测到或低于生物有效阈值。
Objectives of the current studies were to characterize the pattern of GnRH secretion in the cerebrospinal fluid of the bovine third ventricle, determine its correspondence with the tonic and surge release of LH in ovariectomized cows, and examine the dynamics of GnRH pulse generator activity in response to known modulators of LH release (suckling; neuropeptide Y [NPY]). In ovariectomized cows, both tonic release patterns and estradiol-induced surges of GnRH and LH were highly correlated (0.95; p < 0.01). Collectively, LH pulses at the baseline began coincident with (84%) or within one sampling point after (100%) the onset of a GnRH pulse, and all estradiol-induced LH surges were accompanied by corresponding surges of GnRH. A 500-mu g dose of NPY caused immediate cessation of LH pulses and lowered (p < 0.001) plasma concentrations of LH for at least 4 h. This corresponded with declines (p < 0.05) in both GnRH pulse amplitude and frequency, but GnRH pulses were completely inhibited for only 1.5-3 h. In intact, anestrous cows, GnRH poise frequency did not differ before and 48-54 h after weaning on Day 18 postpartum, but concentrations of GnRH (p < 0.05) and amplitudes of GnRH pulses (4 of 7 cows) increased in association with weaning and heightened secretion of LH. We conclude that the study of GnRH secretory dynamics in third-ventricle CSF provides a reasonable approach for examining the activity and regulation of the hypothalamic pulse generator in adult cattle. However, data generated using this approach must be interpreted in their broadest context. Although strong neurally mediated inhibitors of LH pulsatility (suckling; NPY) had robust effects on one or more GnRH secretory characteristics in CSF, only high doses of NPY briefly abolished GnRH pulses. This implies that the GnRH signal received at the hypophyseal portal vessels under these conditions may differ quantitatively or qualitatively from those in CSF, and theoretically would be undetectable or below a biologically effective threshold when LH pulses are absent.