NKCC1 activity modulates formation of functional inhibitory synapses in cultured neocortical neurons
NKCC1 activity modulates formation of functional inhibitory synapses in cultured neocortical neurons
复制标题
DOI：
10.1002/syn.20352
复制
发表时间：
2007-03-01
期刊：
影响因子：
2.3
通讯作者：
Fukuda, Atsuo
中科院分区：
文献类型：
--
作者：
Nakanishi, Keiko;Yamada, Junko;Fukuda, Atsuo
未成熟神经元中的细胞内 Cl- 浓度 ([Cl-](i)) 高于被动分布的预期值，因此氯离子的平衡电位比静息膜电位更正，由此产生的 GABA 使未成熟神经元去极化。未成熟神经元中较高的 [Cl-](i) 被认为是由于 NKCC1（Na+、K+-2Cl(-) 协同转运蛋白）介导的 Cl- 摄取所致。因此，该转运蛋白的功能障碍可能会通过 GABA(A) 受体介导的途径影响突触发育。为了测试这种可能性，我们检查了 Cl-摄取抑制剂对培养的大鼠新皮质神经元突触活动发育的影响。培养过程中用 10 μM 布美他尼长期治疗可降低神经元中突触驱动的节律去极化电位 (RDP) 的幅度，并降低自发抑制性突触后电流 (sIPSC) 的频率，但不会降低自发兴奋性突触后电流 (sEPSC) 的频率。布美他尼长期治疗可减少囊泡 GABA 转运蛋白 (VGAT) 免疫阳性颗粒，而不影响诱发 IPSC (eIPSC) 的配对脉冲比，表明功能性 GABA 能突触数量减少。布美他尼 (10 μM) 急性治疗可降低神经元 [Cl-](i)、RDP 振幅和神经元兴奋性，而荷包牡丹碱存在下布美他尼对 RDP 和神经元兴奋性没有影响。这些结果表明 NKCC1 对 Cl- 的摄取通过促进 GABA 介导的去极化反应来影响抑制性突触的发育。
Intracellular Cl- concentration ([Cl-](i)) in immature neurons is higher than that expected for a passive distribution, therefore the equilibrium potential for chloride is more positive than the resting membrane potential, and the resulting GABA renders immature neurons depolarization. The higher [Cl-](i) in immature neurons is thought to be attributed to the uptake of Cl- mediated by NKCC1 (Na+, K+-2Cl(-)cotransporter). Thus, a dysfunction of this transporter could affect synaptic development through a GABA(A) receptor-mediated pathway. To test this possibility, we examined the effects of a Cl--uptake inhibitor on the development of synaptic activities of rat neocortical neurons in culture. Chronic treatment with bumetanide at 10 mu M during the culture diminished the amplitude of synaptically-driven rhythmic depolarizing potentials (RDPs) in neurons and also decreased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) but not of spontaneous excitatory postsynaptic currents (sEPSCs). Chronic treatment with bumetanide decreased vesicular GABA transporter (VGAT)-immunopositive particles without affecting paired-pulse ratio of evoked IPSCs (eIPSCs), indicating decrease in the number of functional GABAergic synapses. Acute treatment with bumetanide (10 mu M) decreased neuronal [Cl-](i), the amplitude of RDPs, and neuronal excitability, while bumetanide had no effect on RDPs and neuronal excitability in the presence of bicuculline. These results suggest that the uptake of Cl- by NKCC1 affects the development of inhibitory synapses by promoting a depolarizing GABA-mediated response.