Bourguignon J P, Gérard A, Purnelle G, Czajkowski V, Yamanaka C, Lemaître M, Rigo J M, Moonen G, Franchimont P
Department of Pediatrics, CHU Sart Tilman, University of Liège, Belgium.
J Neuroendocrinol. 1997 Mar;9(3):183-91. doi: 10.1046/j.1365-2826.1997.00567.x.
Using antisense oligodeoxynucleotides we aimed to study the role of N-methyl-D-aspartate (NMDA) and gamma-aminobutyric acid (GABA) receptors in the mechanism of Gonadotrophin-releasing hormone (GnRH) secretion in vitro. Since GnRH cell bodies are located in the rat preoptic hypothalamus while most GnRH terminals are in the retrochiasmatic hypothalamus, we compared the effects of oligodeoxynucleotides on explants of the whole (preoptic area included) or retrochiasmatic hypothalamus. When GnRH secretion is evoked by muscimol and NMDA, a time-related reduction of GnRH secretion is caused by antisense oligodeoxynucleotides for the beta subunit of the GABAA receptor and the NR2A subunit of the NMDA receptor, respectively. After 6-7 h, binding studies of tritiated ligands show a decrease in GABA- and NMDA-receptor expression. While these antisense effects are observed using whole explants, no such effects are seen using retrochiasmatic explants, indicating that the facilitatory GABAA and NMDA receptors are encoded in the preoptic area. Using several missense oligodeoxynucleotides or antisense for the NR2B and NR2C subunits of the NMDA receptor, the muscimol- and NMDA-evoked release of GnRH is not affected. When spontaneous pulsatile GnRH secretion is studied, the NR2A antisense oligodeoxynucleotides cause an increase of the interpulse interval. This increase is seen using whole but not retrochiasmatic explants. In contrast, the GABAA and NR2C antisense oligodeoxynucleotides result in a reduction of GnRH interpulse interval. Such a reduction is seen using whole as well as retrochiasmatic explants, indicating that the GABAA and NMDA receptors which mediate inhibition of GnRH pulsatility are encoded in the retrochiasmatic hypothalamus. We conclude that NMDA receptors (NR2A subunit) encoded in the preoptic hypothalamus mediate a facilitatory effect on GnRH pulsatility while GABAA and NMDA (NR2C subunit) receptors encoded in the retrochiasmatic hypothalamus mediate an inhibition of GnRH pulsatility. Pulsatile GnRH secretion is affected differently than the agonist-evoked release of GnRH suggesting that the GnRH secretory neurons and the GnRH pulse generator consist of different cellular entities.
我们使用反义寡脱氧核苷酸来研究N-甲基-D-天冬氨酸（NMDA）和γ-氨基丁酸（GABA）受体在体外促性腺激素释放激素（GnRH）分泌机制中的作用。由于GnRH细胞体位于大鼠视前下丘脑，而大多数GnRH终末位于视交叉后下丘脑，我们比较了寡脱氧核苷酸对整个（包括视前区）或视交叉后下丘脑外植体的作用。当用蝇蕈醇和NMDA诱发GnRH分泌时，GABAA受体β亚基和NMDA受体NR2A亚基的反义寡脱氧核苷酸分别导致GnRH分泌随时间减少。6 - 7小时后，氚标记配体的结合研究显示GABA和NMDA受体表达降低。虽然使用整个外植体可观察到这些反义效应，但使用视交叉后外植体则未观察到此类效应，这表明促进性GABAA和NMDA受体在前视区编码。使用几种错义寡脱氧核苷酸或针对NMDA受体NR2B和NR2C亚基的反义寡脱氧核苷酸，蝇蕈醇和NMDA诱发的GnRH释放不受影响。当研究自发性脉冲式GnRH分泌时，NR2A反义寡脱氧核苷酸导致脉冲间期延长。使用整个外植体可观察到这种延长，但使用视交叉后外植体则未观察到。相反，GABAA和NR2C反义寡脱氧核苷酸导致GnRH脉冲间期缩短。使用整个外植体以及视交叉后外植体均观察到这种缩短，这表明介导对GnRH脉冲性抑制的GABAA和NMDA受体在视交叉后下丘脑编码。我们得出结论，视前下丘脑编码的NMDA受体（NR2A亚基）介导对GnRH脉冲性的促进作用，而视交叉后下丘脑编码的GABAA和NMDA（NR2C亚基）受体介导对GnRH脉冲性的抑制作用。脉冲式GnRH分泌与激动剂诱发的GnRH释放受到不同影响，这表明GnRH分泌神经元和GnRH脉冲发生器由不同的细胞实体组成。
