Roth C, Leonhardt S, Theiling K, Lakomek M, Jarry H, Wuttke W
Children's Hospital, University of Göttingen, Göttingen, Germany.
Brain Res Dev Brain Res. 1998 Sep 10;110(1):105-14. doi: 10.1016/s0165-3806(98)00102-3.
Amino acid neurotransmitters like gamma-aminobutyric acid (GABA) and glutamate (GLU) are involved in the regulation of hypothalamic gonadotropin releasing hormone (GnRH) release. We investigated, whether there are changes of gene expression in the rat hypothalamus for GnRH, GnRH receptor, as well as glutaminase and glutamate decarboxylase, two enzymes regulating neurotransmitter concentrations of GLU and GABA in the brain during the ontogeny. After reverse transcription-polymerase chain reaction (RT-PCR) we used an ELISA method to quantify PCR products. In 15-day old animals high plasma luteinizing hormone (LH) levels with pronounced variations were found. In 25-day old animals LH values were low, whereas in 35-day old rats LH levels increased significantly indicating the reactivation of the GnRH-pulse generator at the beginning of puberty. In parallel to these changes, the mRNA levels of the GnRH receptor in the mediobasal hypothalamus were high at day 15, significantly lower at day 25 and again high at day 35 after birth (ELISA O.D. GnRH-R day 15: 0.46+/-0.07, day 25: 0.16+/-0.04, day 35: 0.36+/-0.04; p<0.01), but no changes of GnRH receptor gene expression were found in the preoptic area. The mRNA of GnRH in the preoptic area as well as mRNA levels of glutaminase and glutamate decarboxylase in the mediobasal hypothalamus and the preoptic area did not change during ontogeny. We conclude that hypothalamic GnRH receptors are involved in the characteristic changes of LH secretion patterns during sexual maturation. Major changes of GnRH receptor gene expression occurred in the mediobasal hypothalamus and correlated well with plasma LH levels, whereas hypothalamic mRNA levels of GnRH, glutaminase and glutamate decarboxylase did not change within the different age groups. Thus the activity of the GABA- and glutamatergic system during ontogeny may be regulated at the receptor or postreceptor level.
γ-氨基丁酸（GABA）和谷氨酸（GLU）等氨基酸神经递质参与下丘脑促性腺激素释放激素（GnRH）释放的调节。我们研究了在个体发育过程中，大鼠下丘脑内GnRH、GnRH受体以及谷氨酰胺酶和谷氨酸脱羧酶（这两种酶调节大脑中GLU和GABA的神经递质浓度）的基因表达是否有变化。经过逆转录-聚合酶链反应（RT-PCR）后，我们使用酶联免疫吸附测定（ELISA）方法对PCR产物进行定量。在15日龄动物中发现血浆促黄体生成素（LH）水平较高且有明显波动。在25日龄动物中LH值较低，而在35日龄大鼠中LH水平显著升高，表明青春期开始时GnRH脉冲发生器重新激活。与这些变化同时，出生后第15天，下丘脑内侧基底部GnRH受体的mRNA水平较高，第25天显著降低，第35天又升高（ELISA光密度值，GnRH-R第15天：0.46±0.07，第25天：0.16±0.04，第35天：0.36±0.04；p<0.01），但在视前区未发现GnRH受体基因表达的变化。视前区GnRH的mRNA以及下丘脑内侧基底部和视前区谷氨酰胺酶和谷氨酸脱羧酶的mRNA水平在个体发育过程中没有变化。我们得出结论，下丘脑GnRH受体参与性成熟过程中LH分泌模式的特征性变化。GnRH受体基因表达的主要变化发生在下丘脑内侧基底部，且与血浆LH水平密切相关，而不同年龄组下丘脑GnRH、谷氨酰胺酶和谷氨酸脱羧酶的mRNA水平没有变化。因此，个体发育过程中GABA能和谷氨酸能系统的活性可能在受体或受体后水平受到调节。
