Pearson K G, Fourtner C R
J Neurophysiol. 1975 Jan;38(1):33-52. doi: 10.1152/jn.1975.38.1.33.
Intracellular recordings were made from the neurites of interneurons and motoneurons in the metathoracic ganglion of the cockroach, Periplaneta americana. Many neurons were penetrated which failed to produce action potentials on the application of large depolarizing currents. Nevertheless, some of them strongly excited and/or inhibited slow motoneurons innervating leg musculature, even with weak depolariziing musculature, even with weak depolarizing currents. Cobalt-sulfide-straining of these nonspiking neurons showed them to be interneurons with their neurites contained entirely within the metathoracic ganglion. Two further characteristics of these interneurons were rapid spontaneous fluctuations in membrane potential and a low resting membrane potential. One nonspiking neuron, interneuron I, when depolarized caused a strong excitation of the set of slow levator motoneurons which discharge in bursts during stepping movements of the metathoracic leg. During rhythmic leg movements the membrane potential of interneuron I oscillated with the depolarizing phases occurring at the same time as bursts of activity in the levator motorneurons. No spiking or any other nonspiking neuron was penetrated which could excite these levator motoneurons. From all these observations we conclude that oscillations in the membrane potential of interneuron I are entirely responsible for producing the levator bursts, and thus for producing stepping movements in a walking animal. During rhythmic leg movements, bursts of activity in levator and depressor motoneurons are initiated by slow graded depolarizations. The similarity of the synaptic activity in these two types of motoneurons suggests that burst activity in the depressor motoneurons is also produced by rhythmic activity in nonspiking interneurons. The fact that no spiking neuron was found to excite the depressor motoneurons supports this conclusion. Interneuron I is also an element of the rhythm-generating system, since short depolarizing pulses applied to it during rhythmic activity could reset the thythm. Long-duration current pulses applied to interneuron I in a quiescent animal did not produce rhythmic activity. This observation, together with the finding that during rhythmic activity the slow depolarizations in interneuron I are usually terminated by IPSPs, suggests that interneuron I alone does not generate the rhythm. No spiking interneurons have yet been enccountered which influence the activity in levator motoneurons. Thus, we conclude that the rhythm is generated in a network of nonspiking interneurons. The cellular mechanisms for generating the oscillations in this network are unknown. Continued.
对美洲大蠊后胸神经节中的中间神经元和运动神经元的神经突进行了细胞内记录。刺入了许多神经元，在施加较大的去极化电流时它们未能产生动作电位。然而，其中一些神经元即使在施加微弱的去极化电流时，也能强烈兴奋和/或抑制支配腿部肌肉组织的慢运动神经元。对这些无锋电位神经元进行硫化钴染色显示它们是中间神经元，其神经突完全包含在后胸神经节内。这些中间神经元的另外两个特征是膜电位的快速自发波动和较低的静息膜电位。一个无锋电位神经元，即中间神经元I，去极化时会强烈兴奋一组慢提肌运动神经元，这些神经元在后胸腿的步进运动期间成簇放电。在有节奏的腿部运动期间，中间神经元I的膜电位振荡，去极化阶段与提肌运动神经元的活动爆发同时发生。没有刺入能兴奋这些提肌运动神经元的锋电位或任何其他无锋电位神经元。从所有这些观察结果我们得出结论，中间神经元I的膜电位振荡完全负责产生提肌爆发，从而负责在行走动物中产生步进运动。在有节奏的腿部运动期间，提肌和降肌运动神经元的活动爆发由缓慢的分级去极化启动。这两种类型运动神经元中突触活动的相似性表明，降肌运动神经元中的爆发活动也由无锋电位中间神经元的节律性活动产生。未发现锋电位神经元能兴奋降肌运动神经元这一事实支持了这一结论。中间神经元I也是节律产生系统的一个组成部分，因为在节律性活动期间施加于它的短去极化脉冲可以重置节律。在静止动物中施加于中间神经元I的长时间电流脉冲不会产生节律性活动。这一观察结果，连同在节律性活动期间中间神经元I中的缓慢去极化通常由抑制性突触后电位终止这一发现，表明仅中间神经元I不会产生节律。尚未遇到影响提肌运动神经元活动的锋电位中间神经元。因此，我们得出结论，节律是在无锋电位中间神经元网络中产生的。该网络中产生振荡的细胞机制尚不清楚。续
