Watanabe A, Obara S, Akiyama T
J Gen Physiol. 1968 Dec;52(6):908-24. doi: 10.1085/jgp.52.6.908.
The pacemaker neurons of the Squilla heart ganglion are innervated from the CNS through three pairs of extrinsic nerves. One of them, the alpha-nerve, is inhibitory to the heart beat. The effect of alpha-nerve stimulation on the pacemaker potential was examined with intracellular electrodes. Without extrinsic nerve stimulation the membrane potential of the pacemaker cell fluctuated spontaneously. On application of a tetanic train of stimuli to the alpha-nerve the membrane potential was shifted and fixed to a steady level, which with K(2)SO(4)-filled electrodes was near the peak of hyperpolarization after a spontaneous burst, but was less negative with KCl-filled electrodes. The shift of the membrane potential was due to the summated IPSP's. By changing the level of the membrane potential with injection of the polarizing current the IPSP could be reversed in sign, and the size of the IPSP was linearly correlated with the membrane potential level. During inhibition the membrane conductance increased. The increase depended on divalent cation concentrations in the outside medium. In Ca-rich saline the IPSP was greatly enhanced. In Mg-rich saline it was suppressed. The amplitude of antidromic spikes was reduced during inhibition especially when the spike frequency was high.
虾蛄心脏神经节的起搏神经元通过三对外周神经接受来自中枢神经系统的支配。其中一对，即α神经，对心跳具有抑制作用。用细胞内电极研究了α神经刺激对起搏电位的影响。在没有外周神经刺激的情况下，起搏细胞的膜电位自发波动。当向α神经施加一串强直刺激时，膜电位发生偏移并稳定在一个稳定水平，使用硫酸钾填充电极时，该水平接近自发爆发后的超极化峰值，但使用氯化钾填充电极时负极性较小。膜电位的偏移是由于IPSP的总和。通过注入极化电流改变膜电位水平，IPSP的极性可以反转，并且IPSP的大小与膜电位水平呈线性相关。在抑制期间，膜电导增加。这种增加取决于外部介质中的二价阳离子浓度。在富含钙的盐溶液中，IPSP大大增强。在富含镁的盐溶液中，它受到抑制。在抑制期间，尤其是当动作电位频率较高时，逆向动作电位的幅度减小。
