Morita K, North R A
Neuroscience. 1985 Feb;14(2):661-72. doi: 10.1016/0306-4522(85)90317-3.
Intracellular recordings were made from neurones in myenteric ganglia of the guinea-pig ileum in vitro. Synaptic potentials were evoked by electrically stimulating presynaptic fibres as they entered the ganglion, using a small focal electrode. Slow synaptic depolarizations (excitatory postsynaptic potentials) were evoked in most myenteric neurones of both types. A single stimulus was more likely to evoke a slow excitatory postsynaptic potential in cells with nicotinic synaptic input (S cells; 50%) than in cells with long-lasting after-hyperpolarizations following the soma action potential (AH cells; 20%). Two pulses often evoked a slow excitatory postsynaptic potential in AH cells when one pulse was ineffective. The optimally effective time between the pulses was about 100 ms. Ten pulses resulted in slow excitatory postsynaptic potentials even when delivered at frequencies as low as 0.5 Hz. For the same frequency of presynaptic stimulation, the duration of the slow excitatory postsynaptic potential was greater in AH cells than in S cells and the amplitude of the slow excitatory postsynaptic potential was slightly greater in S than AH cells. Spontaneous depolarizations were observed which had time-courses and amplitudes similar to the evoked slow excitatory postsynaptic potential. They were not blocked by tetrodotoxin or atropine. The calcium-dependent after-hyperpolarization which follows one or more action potentials in AH cells was reduced or even abolished during the slow excitatory postsynaptic potential. Presynaptic nerve stimulation at intensities lower than those required to cause a slow excitatory postsynaptic potential caused a reduction in the calcium dependent after-hyperpolarization. It is concluded that the slow excitatory postsynaptic potential is generated by an intracellular intermediate process which is sensitive to the intracellular calcium concentration. The results suggest that the postsynaptic action of the synaptic transmitter is to interfere with the intracellular process which couples the entry of calcium to the increase in potassium conductance.
在体外对豚鼠回肠肌间神经节中的神经元进行细胞内记录。使用一个小的聚焦电极，通过电刺激进入神经节的突触前纤维来诱发突触电位。两种类型的大多数肌间神经元都能诱发缓慢的突触去极化（兴奋性突触后电位）。单个刺激在具有烟碱型突触输入的细胞（S细胞；50%）中比在胞体动作电位后具有持久超极化后的细胞（AH细胞；20%）中更有可能诱发缓慢的兴奋性突触后电位。当单个脉冲无效时，两个脉冲常常能在AH细胞中诱发缓慢的兴奋性突触后电位。脉冲之间的最佳有效时间约为100毫秒。即使以低至0.5赫兹的频率发放，十个脉冲也能产生缓慢的兴奋性突触后电位。对于相同频率的突触前刺激，AH细胞中缓慢兴奋性突触后电位的持续时间比S细胞中的长，而S细胞中缓慢兴奋性突触后电位的幅度比AH细胞中的略大。观察到了自发去极化，其时间进程和幅度与诱发的缓慢兴奋性突触后电位相似。它们不受河豚毒素或阿托品的阻断。在缓慢兴奋性突触后电位期间，AH细胞中一个或多个动作电位之后的钙依赖性超极化会降低甚至消失。低于引起缓慢兴奋性突触后电位所需强度的突触前神经刺激会导致钙依赖性超极化降低。结论是，缓慢兴奋性突触后电位是由一个对细胞内钙浓度敏感的细胞内中间过程产生的。结果表明，突触递质的突触后作用是干扰将钙的进入与钾电导增加相耦合的细胞内过程。
