滋阴泻火中药对下丘脑GnRH的合成、分泌及其调节机制的影响

目的：探讨滋肾阴泻相火（简称滋阴泻火）中药对下丘脑促性腺激素释放激素（GnRH)的合成、分泌及其调节机制的影响。方法：青春大白喂饲滋阴泻火中药后，采用内侧基底下丘脑区的脑片孵育法，测定KCl刺激后孵育液中GnRH的含量观察其正丘脑GnRH的紧张性分泌中心（弓状核及腹内侧核）GnRH成水平的变化，采用免疫组化及计算机图像处理技术，测定其下丘脑视前区GnRH阳性的积分光密芳值，观察其下丘脑GnRH的脉冲性分泌中心（视前内侧核）GnRH含量的变化；采用下丘脑的内侧视前区的挽灌流技术，以放射免疫法测序列的灌注流中GnRH的含量，观察其下丘脑视前内侧核GnRH脉冲释放频率及幅度的变化；以高效液相色谱－荧光检测法，测定灌注液中门冬氨酸，谷氨酸及γ氨基酸的含量，并以放射免疫法测定灌流液中β-内啡肽的含量，观察其正丘脑GnRH的脉冲性分泌中心（视前内侧核区）兴奋性、抑制性氨基酸递质及β-内啡肽放量的变化。结果：滋阴泻火中药可使内侧基底下丘脑区（弓状核、腹内侧核）及下丘脑视前区（视前内侧核）的GnRH含量显著减少，并可使下丘脑视前内侧核GnRH脉冲释放的频率及幅度明显降低，滋阴泻火中还可使下丘脑内侧视前区门冬氨酸和谷氨酸的释放明显减少，而使γ氨基丁酸和β-内啡肽的释放明显增加。结论：滋阴泻火中药可通过抑制中枢兴奋性氨基酸递质的释放及促进中枢抑制性氨基酸递质和β-内啡肽的放明显增加。结论：滋阴泻火中药可通过抑制中枢奋性氨基酸递质的释放井枢抑制性氨基酸递质和β-内啡肽的释放，使下丘脑GnRH神经元的功能活动显著降低，从而使下丘脑GnRH的紧张性分泌中心和脉冲性分泌中心GnRH的合成及分泌明显减少，这可能是滋阴泻火中药能有效地治疗特发性真性早熟的主要作用机理之一。

Effect of Chinese Herbal Medicine for Nourishing Yin and Removing Fire on Biosynthesis, Secretion and Regulative Mechanism of Gonadotropin-Releasing Hormone in Hypothalamus

OBJECTIVE: To elucidate the effect of Chinese herbal medicine (CHM) for nourishing Yin and removing fire on the biosynthesis, secretion and regulative mechanism of gonadotropin-releasing hormone (GnRH) in hypothalamus. METHODS: The brain slices of medial basal hypothalamus of adolescent rats, which had been fed with CHM, were incubated. The content of GnRH in incubative liquid was determined during the slices were stimulating with high KC1 to observe the change of GnRH biosynthesis from tonic secretory center of GnRH (arcuate nucleus and ventromedial nucleus) in hypothalamus. The integrated optic density of GnRH positive immunoreactive substance in preoptic area of hypothalamus was determined by immunohistochemistry and image processing to observe the change of GnRH content in pulsative secretory center of GnRH (medial preoptic nucleus) in hypothalamus. The push-pull perfusion of medial preoptic area in hypothalamus was performed. The content of GnRH in serial perfusates was determined by radioimmunoassay (RIA) to observe the change of frequency and amplitude of GnRH pulse releasing from medial preoptic area in hypothalamus. The content of aspartic acid, glutamic acid and gamma-amino butyric acid in the perfusate was determined by high performance liquid chromatography-fluorometry, and the content of beta-endorphic in the perfusate was determined by RIA to observe the change of releasing amount of exciting aminoacid neurotransmitter and beta-endorphin from pulsative secretory center of GnRH (medial preoptic area) in hypothalamus. RESULTS: CHM could markedly reduce the content of GnRH in medial basal hypothalamus (arcuate nucleus and veatromeolial nucleus) and preoptic area (meolical preoptic nucleus) of hypothalamus, and could obviously lower the frequency and amplitude of GnRH pulse releasing from medial preoptic nucleus, It also could markedly decrease the releasing amount of aspartic acid and glutamic acid, while obviously increase the releasing amount of gamma-amino butyric acid and beta-endorphin from medial preoptic area of hypothalamus. CONCLUSION: CHM could markedly reduce the activity of GnRH neurons in hypothalamus through inhibiting the releasing of central exciting aminoacid neurotransmitter and promoting the releasing of central inhibiting aminoacid neurotransmitter and beta-endorphin, thereby, obviously decrease the biosynthesis and secretion of GnRH from tonic and pulsative secretory center of GnRH in hypothalamus. It could be one of chief effective mechanism of CHM in efficiently treating the idiopathic precocious puberty.