Department of Physiology, Michigan State University, East Lansing, MI 48824, USA.
J Neurophysiol. 2011 Jun;105(6):2920-30. doi: 10.1152/jn.00684.2010. Epub 2011 Apr 13.
Unitary excitatory (EPSP) and inhibitory (IPSP) postsynaptic potentials (PSPs) were evoked between neurons in Rexed's laminae (L)II-V of spinal slices from young hamsters (7-24 days old) at 27°C using paired whole cell recordings. Laminar differences in synaptic efficacy were observed: excitatory connections were more secure than inhibitory connections in LII and inhibitory linkages in LII were less reliable than those in LIII-V. A majority of connections displayed paired-pulse facilitation or depression. Depression was observed for both EPSPs and IPSPs, but facilitation was seen almost exclusively for IPSPs. There were no frequency-dependent shifts between facilitation and depression. Synaptic depression was associated with an increased failure rate and decreased PSP half-width for a majority of connections. However, there were no consistent changes in failure rate or PSP time course at facilitating connections. IPSPs evoked at high-failure synapses had consistently smaller amplitude and showed greater facilitation than low-failure connections. Facilitation at inhibitory connections was positively correlated with synaptic jitter and associated with a decrease in latency. At many connections, the paired-pulse ratio varied from trial to trial and depended on the amplitude of the first PSP; dependence was greater for inhibitory synapses than excitatory synapses. Paired-pulse ratios for connections onto neurons with rapidly adapting, "phasic" discharge to depolarizing current injection were significantly greater than for connections onto neurons with tonic discharge properties. These results are evidence of diversity in synaptic transmission between dorsal horn neurons, the nature of which may depend on the types of linkage, laminar location, and intrinsic firing properties of postsynaptic cells.
在 27°C 下，使用成对全细胞记录法，在来自年轻仓鼠（7-24 天）的脊髓切片的雷克斯德氏层（L）II-V 中的神经元之间诱发了单一兴奋性（EPSP）和抑制性（IPSP）突触后电位（PSP）。观察到突触效能的层间差异：在 LII 中兴奋性连接比抑制性连接更可靠，而在 LII 中抑制性连接比 LIII-V 中的更不可靠。大多数连接显示出成对脉冲易化或抑制。观察到 EPSP 和 IPSP 的抑制，但易化几乎仅见于 IPSP。在易化和抑制之间没有频率依赖性的转变。突触抑制与大多数连接的失败率增加和 PSP 半宽度减小有关。然而，在促进连接时，失败率或 PSP 时程没有一致的变化。在高失败率突触诱发的 IPSP 始终具有较小的幅度，并且比低失败率连接表现出更大的易化。抑制性连接的易化与突触抖动呈正相关，并与潜伏期降低有关。在许多连接中，成对脉冲比在试验之间变化，并且取决于第一个 PSP 的幅度；抑制性突触比兴奋性突触的依赖性更大。对具有快速适应、“相位”放电对去极化电流注入的神经元的连接的成对脉冲比对于具有紧张放电特性的神经元的连接具有显著更大的比值。这些结果证明了背角神经元之间的突触传递的多样性，其性质可能取决于连接的类型、层间位置和突触后细胞的固有放电特性。
