Krsmanović L Z, Stojilković S S, Merelli F, Dufour S M, Virmani M A, Catt K J
Endocrinology and Reproduction Research Branch, Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892.
Proc Natl Acad Sci U S A. 1992 Sep 15;89(18):8462-6. doi: 10.1073/pnas.89.18.8462.
Gonadotropin-releasing hormone (GnRH) is released episodically into the pituitary portal vessels and from hypothalamic tissue of male and female rats in vitro. Perifused primary cultures of rat hypothalamic neurons, as well as the GT1-1 GnRH neuronal cell line, spontaneously exhibited episodic GnRH secretion of comparable frequency to that observed with perifused hypothalami. Such pulsatile GnRH release from GT1 cells indicates that GnRH neurons generate rhythmic secretory activity in the absence of input from other cell types. In primary hypothalamic cultures, the frequency of GnRH pulses increased with the duration of culture. The spontaneous pulsatility in GnRH release was abolished in Ca(2+)-deficient medium and was markedly attenuated in the presence of nifedipine, an antagonist of voltage-sensitive Ca2+ channels. The basal intracellular Ca2+ level of perifused GT1-1 cells cultured on coverslips was also dose-dependently reduced by nifedipine. Conversely, depolarization with high K+ increased intracellular Ca2+ and GnRH release in an extracellular Ca(2+)-dependent and nifedipine-sensitive manner. The dihydropyridine Ca2+ channel agonist Bay K 8644 increased basal and K(+)-induced elevations of intracellular Ca2+ concentration and GnRH secretion. These findings demonstrate that pulsatile neuropeptide secretion is an intrinsic property of GnRH neuronal networks and is dependent on voltage-sensitive Ca2+ influx for its maintenance.
促性腺激素释放激素（GnRH）呈阵发性释放到垂体门脉血管中，并且在体外可从雄性和雌性大鼠的下丘脑组织中释放出来。大鼠下丘脑神经元的灌流原代培养物以及GT1-1 GnRH神经元细胞系，自发地表现出与灌流下丘脑所观察到的频率相当的阵发性GnRH分泌。GT1细胞的这种脉冲式GnRH释放表明，GnRH神经元在没有其他细胞类型输入的情况下产生节律性分泌活动。在原代下丘脑培养物中，GnRH脉冲的频率随着培养时间的延长而增加。GnRH释放的自发搏动性在缺钙培养基中消失，并且在电压敏感性Ca2+通道拮抗剂硝苯地平存在的情况下明显减弱。在盖玻片上培养的灌流GT1-1细胞的基础细胞内Ca2+水平也因硝苯地平而呈剂量依赖性降低。相反，高钾去极化以细胞外Ca2+依赖和硝苯地平敏感的方式增加细胞内Ca2+和GnRH释放。二氢吡啶Ca2+通道激动剂Bay K 8644增加基础和钾诱导的细胞内Ca2+浓度升高以及GnRH分泌。这些发现表明，脉冲式神经肽分泌是GnRH神经元网络的固有特性，并且其维持依赖于电压敏感性Ca2+内流。
