Canonaco M, Carelli A, Maggi A
Zoology Laboratory, University of Calabria, Italy.
Neuroendocrinology. 1993 May;57(5):965-73. doi: 10.1159/000126461.
The effects of sex steroid hormones on the different receptor binding sites of the GABAA molecule remain unclear. In this report we have demonstrated, using autoradiography techniques, that the distribution pattern of the benzodiazepine receptors (a component of the GABAA molecule) in some extrahypothalamic brain regions is altered by both in vivo and in vitro sex steroid hormone treatment. In vivo administration of the sex steroids estradiol and progesterone induced a significant change in [3H]flunitrazepam (benzodiazepine agonist) binding levels in the amygdala, and cortico and posterior brain nuclei of the female rat. In fact, elevated and diminished receptor-binding levels were obtained in the corticomedial amygdala nucleus and in the pontine central gray matter respectively, following the administration of estradiol. Significant hormonal effects were also shown for animals that received only a progesterone dose, as demonstrated by the increased and decreased receptor levels in the basolateral amygdala nucleus and cortex lamina VI and in the substantia nigra pars reticulata, respectively. It was interesting, at this point, to investigate whether the hormone effects on [3H]flunitrazepam binding changes might be mediated through a GABA-dependent activity, because the benzodiazepine and GABAA receptors are coupled to a chloride ion channel in an allosteric manner. When 50 microM GABA was added to the incubation medium, substantially altered binding levels were recorded in animals that received progesterone replacement therapy only. The GABA-induced progesterone effects both increased substantially the binding levels in the oriens-pyramidalis CA1 layer of the hippocampus and in the intermediate gray layer of the superior colliculus as well as reducing receptor levels in the substantia nigra pars reticulata.(ABSTRACT TRUNCATED AT 250 WORDS)
性类固醇激素对γ-氨基丁酸A型（GABAA）分子不同受体结合位点的影响尚不清楚。在本报告中，我们使用放射自显影技术证明，体内和体外性类固醇激素处理均会改变某些下丘脑外脑区苯二氮䓬受体（GABAA分子的一个组成部分）的分布模式。对雌性大鼠体内施用性类固醇雌二醇和孕酮会导致杏仁核、大脑皮质及后脑核中[3H]氟硝西泮（苯二氮䓬激动剂）结合水平发生显著变化。事实上，施用雌二醇后，皮质内侧杏仁核和脑桥中央灰质中的受体结合水平分别升高和降低。仅接受孕酮剂量的动物也显示出显著的激素效应，分别表现为基底外侧杏仁核、皮质第VI层和黑质网状部中受体水平的增加和降低。此时，研究激素对[3H]氟硝西泮结合变化的影响是否可能通过GABA依赖性活性介导很有意思，因为苯二氮䓬受体和GABAA受体以变构方式与氯离子通道偶联。当向孵育培养基中添加50微摩尔GABA时，仅接受孕酮替代疗法的动物记录到结合水平发生了显著改变。GABA诱导的孕酮效应既显著增加了海马体的梨状细胞层CA1区和上丘中间灰质层的结合水平，也降低了黑质网状部的受体水平。（摘要截选至250字）
