Deuchars J, Thomson A M
Department of Physiology, Royal Free Hospital School of Medicine, London, U.K.
Neuroscience. 1996 Oct;74(4):1009-18. doi: 10.1016/0306-4522(96)00251-5.
In adult rat hippocampus, simultaneous intracellular recordings from 989 pairs of CA1 pyramidal cells revealed nine monosynaptic, excitatory connections. Six of these pairs were sufficiently stable for electrophysiological analysis. Mean excitatory postsynaptic potential amplitude recorded at a postsynaptic membrane potential between -67 and -70 mV was 0.7 +/- 0.5 mV (0.17-1.5 mV), mean 10-90% rise time was 2.7 +/- 0.9 ms (1.5-3.8 ms) and mean width at half-amplitude was 16.8 +/- 4.1 ms (11.6-25 ms). Cells were labelled with biocytin and identified histologically. For one pair that was fully reconstructed morphologically, excitatory postsynaptic potential average amplitude was 1.5 mV, 10-90% rise time 2.8 ms and width at half-amplitude 11.6 ms (at -67 mV). In this pair, correlated light and electron microscopy revealed that the presynaptic axon formed two synaptic contacts with third-order basal dendrites of the postsynaptic pyramid, one with a dendritic spine, the other with a dendritic shaft. In the four pairs tested, postsynaptic depolarization increased excitatory postsynaptic potential amplitude and duration. In two, D-2-amino-5-phosphonovalerate (50 microM) reduced the amplitude and duration of the excitatory postsynaptic potential. The remainder of the excitatory postsynaptic potential now increased with postsynaptic hyperpolarization and was abolished by 20 microM 6-cyano-7-nitroquinoxaline-2,3-dione (n = 1). Paired-pulse depression was evident in the four excitatory postsynaptic potentials tested. This depression decreased with increasing inter-spike interval. These results provide the first combined electrophysiological and morphological illustration of synaptic contacts between pyramidal neurons in the hippocampus and confirm that connections between CA1 pyramidal neurons are mediated by both N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate/kainate receptors.
在成年大鼠海马体中，对989对CA1锥体神经元进行同步细胞内记录，发现了9个单突触兴奋性连接。其中6对连接足够稳定，可用于电生理分析。在-67至-70 mV的突触后膜电位下记录的平均兴奋性突触后电位幅度为0.7±0.5 mV（0.17 - 1.5 mV），平均10 - 90%上升时间为2.7±0.9 ms（1.5 - 3.8 ms），半幅度处的平均宽度为16.8±4.1 ms（11.6 - 25 ms）。细胞用生物素标记并进行组织学鉴定。对于一对在形态上完全重建的神经元，兴奋性突触后电位平均幅度为1.5 mV，10 - 90%上升时间为2.8 ms，半幅度处宽度为11.6 ms（在-67 mV时）。在这对神经元中，相关的光学和电子显微镜显示，突触前轴突与突触后锥体神经元的三级基底树突形成了两个突触接触，一个与树突棘接触，另一个与树突干接触。在测试的4对神经元中，突触后去极化增加了兴奋性突触后电位的幅度和持续时间。在2对神经元中，D - 2 - 氨基 - 5 - 磷酸戊酸（50 μM）降低了兴奋性突触后电位的幅度和持续时间。现在，其余的兴奋性突触后电位随着突触后超极化而增加，并被20 μM的6 - 氰基 - 7 -硝基喹喔啉 - 2,3 -二酮所消除（n = 1）。在测试的4个兴奋性突触后电位中，配对脉冲抑制明显。这种抑制随着峰间间隔的增加而减小。这些结果首次提供了海马体中锥体神经元之间突触接触的电生理和形态学联合例证，并证实CA1锥体神经元之间的连接由N - 甲基 - D - 天冬氨酸和α - 氨基 - 3 - 羟基 - 5 - 甲基 - 4 -异恶唑丙酸/海人藻酸受体介导。
