Benzodiazepines block alpha2-containing inhibitory glycine receptors in embryonic mouse hippocampal neurons.
Benzodiazepines block alpha2-containing inhibitory glycine receptors in embryonic mouse hippocampal neurons.
复制标题
DOI：
10.1152/jn.00612.2002
复制
发表时间：
2003-07
影响因子：
2.5
通讯作者：
L. Thio;A. Shanmugam;K. Isenberg;Kelvin A. Yamada
中科院分区：
文献类型：
--
作者：
L. Thio;A. Shanmugam;K. Isenberg;Kelvin A. Yamada
哺乳动物皮质中的抑制性甘氨酸受体（GlyR）可能有助于大脑发育和维持强直抑制。鉴于它们遍布整个皮层，它们的调节可能会产生重要的生理后果。尽管苯二氮卓类药物可增强 γ-氨基丁酸 A 受体 (GABAAR)，但它们也可能调节 GlyR，因为结合研究最初表明它们作用于 GlyR。此外，它们增强新生儿 GABAAR 的能力减弱表明它们可能在发育中大脑的另一个部位发挥其有益的临床作用。因此，我们研究了苯二氮卓类药物对培养的胚胎小鼠海马神经元中 GlyR 介导的全细胞电流的影响。首先，我们确定了该制剂中的 GlyR 亚基组成。甘氨酸、β-丙氨酸和牛磺酸以剂量依赖性方式激活士的宁敏感的氯电流。三种激动剂的最大浓度产生与完全激动剂预期相同的、非加性的反应。 GlyR 电流的药理学特性，包括印防毒素、印防肽和托烷司琼的调节模式，表明 GlyR 由 α2β 异聚体和 α2 同聚体组成。逆转录酶聚合酶链反应 (RTPCR) 研究证实了 α2 和 β 亚基的存在。其次，我们发现微摩尔浓度的一些苯二氮卓类药物（包括利眠宁和硝西泮）会抑制 GlyR 电流。硝西泮对 GlyR 的抑制是非竞争性的，不依赖于电压，并且不反映增强的脱敏作用。因此，苯二氮卓类药物通过“低”亲和力位点变构抑制胚胎小鼠海马神经元中含有α2的GlyR。
Inhibitory glycine receptors (GlyRs) in the mammalian cortex probably contribute to brain development and to maintaining tonic inhibition. Given their presence throughout the cortex, their modulation likely has important physiological consequences. Although benzodiazepines potentiate gamma-aminobutyric acidA receptors (GABAARs), they may also modulate GlyRs because binding studies initially suggested that they act at GlyRs. Furthermore, their diminished ability to potentiate neonatal GABAARs suggests that they may exert their beneficial clinical effects at another site in the developing brain. Therefore we examined the effect of benzodiazepines on whole cell currents mediated by GlyRs in cultured embryonic mouse hippocampal neurons. First, we determined the GlyR subunit composition in this preparation. Glycine, beta-alanine, and taurine activate strychnine-sensitive chloride currents in a dose-dependent manner. Maximal concentrations of the three agonists produce equal, nonadditive responses as expected of full agonists. The pharmacological properties of the GlyR currents including their pattern of modulation by picrotoxinin, picrotin, and tropisetron indicate that GlyRs consist of alpha2beta heteromers and alpha2 homomers. Reverse transcriptase polymerase chain reaction (RTPCR) studies confirmed the presence of alpha2 and beta subunits. Second, we found that micromolar concentrations of some benzodiazepines, including chlordiazepoxide and nitrazepam, inhibit GlyR currents. Nitrazepam inhibition of GlyRs is noncompetitive, is not voltage dependent, and does not reflect enhanced desensitization. Thus benzodiazepines allosterically inhibit alpha2-containing GlyRs in embryonic mouse hippocampal neurons via a "low"-affinity site.