Gottmann K, Pfrieger F W, Lux H D
Max-Planck-Institute for Psychiatry, Department of Neurophysiology, Planegg-Martinsried, Germany.
Brain Res Dev Brain Res. 1994 Aug 12;81(1):77-88. doi: 10.1016/0165-3806(94)90070-1.
The formation of synapses between cultured rat thalamic neurons was studied with electrophysiological and immunocytochemical methods. Thalamic neurons in culture form predominantly glutamatergic synapses. Already after 3 days in vitro glutamatergic miniature EPSCs occurred spontaneously and their frequency was strongly increased after K+ depolarization, while GABAergic mIPSCs were found after K+ depolarization at lower frequency. This demonstrates that both, excitatory glutamatergic and inhibitory GABAergic synapses were functional in close succession to initial neurite outgrowth. Synapses formed independent of spontaneous electrical activity, which was absent during the first week in culture. Spontaneous action potentials appeared during the second week and chronic action potential blockade by addition of tetrodotoxin reduced neuronal survival and the number of glutamatergic synapses per neuron. During in vitro differentiation the number of synapsin I immunoreactive presynaptic terminals and the frequency of spontaneous glutamatergic miniature EPSCs increased closely correlated, while the frequency of GABAergic mIPSCs after K+ depolarization did not increase. Thus, the continous formation of presynaptic terminals, including possible maturation of transmitter release, appeared to underlie the increase in mEPSC frequency. Analysis of miniature EPSC amplitudes at different stages in vitro revealed an increase in amplitudes, suggesting synaptic differentiation after initial establishment of functional transmission in glutamatergic synapses. This process was synapse specific as amplitudes of GABAergic mIPSCs were invariant.
采用电生理和免疫细胞化学方法研究了培养的大鼠丘脑神经元之间突触的形成。培养的丘脑神经元主要形成谷氨酸能突触。体外培养3天后，谷氨酸能微小兴奋性突触后电流（mEPSCs）就自发出现，钾离子去极化后其频率显著增加，而钾离子去极化后以较低频率发现γ-氨基丁酸能微小抑制性突触后电流（mIPSCs）。这表明，兴奋性谷氨酸能突触和抑制性γ-氨基丁酸能突触在神经突最初长出后不久就开始发挥功能。突触的形成独立于自发电活动，培养的第一周不存在自发电活动。自发动作电位在第二周出现，添加河豚毒素进行慢性动作电位阻断会降低神经元存活率以及每个神经元的谷氨酸能突触数量。在体外分化过程中，突触素I免疫反应性突触前终末的数量与自发谷氨酸能微小兴奋性突触后电流的频率密切相关地增加，而钾离子去极化后γ-氨基丁酸能微小抑制性突触后电流的频率没有增加。因此，突触前终末的持续形成，包括递质释放可能的成熟，似乎是微小兴奋性突触后电流频率增加的基础。对体外不同阶段微小兴奋性突触后电流幅度的分析显示幅度增加，表明谷氨酸能突触在功能传递初步建立后发生了突触分化。这一过程具有突触特异性，因为γ-氨基丁酸能微小抑制性突触后电流的幅度没有变化。
