Ramirez V D, Dluzen D E
Biol Reprod. 1987 Feb;36(1):59-76. doi: 10.1095/biolreprod36.1.59.
In this report, we have reviewed recent information gathered by probing with a push-pull cannula (PPC) the in vivo activity of the suprachiasmatic nucleus (SCN), hypothalamus, and anterior pituitary gland of freely moving animals. In male and female rats, probing of the SCN with the PPC revealed distinct oscillatory patterns of 5-hydroxy indole-acetic acid (5-HIAA) output very much dependent on the position of the cannula. In males, it was also possible to demonstrate, for the first time, in vivo output of immunoreactive vasopressin (VP) most likely from the SCN. Interestingly, the output of VP was stimulated by local activation of probable 5-hydroxytryptamine (5-HT) terminals with 5-hydroxytryptophan (5-HTP), a precursor of 5-HT synthesis. Probing the hypothalamus of rats and rabbits revealed that the in vivo release of luteinizing hormone-releasing hormone (LHRH) (frequency and amplitude of the LHRH signal) can be altered by administration of estrogen to ovariectomized rats; in both species, progesterone stimulated the amplitude of the LHRH signal, but only when this steroid was infused in pulses--the physiological mode of circulating progesterone in the rat. Further, in male rabbits, pulses of progesterone did not stimulate LHRH release. Last, probing the anterior pituitary with the PPC revealed that a series of push-pull perfusions could be performed in the same animal under different experimental conditions for nearly 60 days of experimentation. It also resolved the apparent paradox that after castration, decreased instead of increased activity of the neural LHRH apparatus was noticed when the PPC was positioned in the hypothalamus. Moving the PPC to the anterior pituitary revealed that castration was accompanied by an increase in the amplitude and frequency of the LHRH signals arriving in the anterior pituitary of castrated male rats. This mode of operation of the LHRH pulse generator is clearly compatible with the mode of luteinizing hormone (LH) release in gonadectomized animals. Finally, based on these results, a hypothetical model of the operation of the LHRH pulse generator has been proposed.
在本报告中，我们回顾了通过使用推挽套管（PPC）探测自由活动动物的视交叉上核（SCN）、下丘脑和垂体前叶的体内活性所收集到的最新信息。在雄性和雌性大鼠中，用PPC探测SCN发现5-羟色胺酸（5-HIAA）输出呈现出明显的振荡模式，这在很大程度上取决于套管的位置。在雄性大鼠中，还首次证明了视交叉上核很可能是体内免疫反应性加压素（VP）的输出部位。有趣的是，5-羟色胺（5-HT）合成的前体5-羟色氨酸（5-HTP）对可能的5-HT终末的局部激活刺激了VP的输出。探测大鼠和兔子的下丘脑发现，对去卵巢大鼠施用雌激素可改变促黄体生成素释放激素（LHRH）的体内释放（LHRH信号的频率和幅度）；在这两个物种中，孕酮刺激了LHRH信号的幅度，但只有当这种类固醇以脉冲形式注入时才会如此——这是大鼠体内孕酮循环的生理模式。此外，在雄性兔子中，孕酮脉冲并未刺激LHRH释放。最后，用PPC探测垂体前叶发现，在近60天的实验中，可以在同一动物的不同实验条件下进行一系列推挽灌注。这也解决了一个明显的矛盾，即阉割后，当PPC位于下丘脑时，神经LHRH装置的活性反而降低而不是增加。将PPC移至垂体前叶发现，阉割伴随着到达阉割雄性大鼠垂体前叶的LHRH信号的幅度和频率增加。LHRH脉冲发生器的这种运作模式显然与性腺切除动物中促黄体生成素（LH）的释放模式相符。最后，基于这些结果，提出了一个LHRH脉冲发生器运作的假设模型。
