Pearlstein E, Watson A H, Bévengut M, Cattaert D
Laboratoire Neurobiologie et Mouvements, CNRS, Marseille, France.
J Comp Neurol. 1998 Sep 21;399(2):241-54.
The inhibitory relationship between two antagonistic groups of motor neurones (MNs) that control the second leg joint of the crayfish Procambarus clarkii, was investigated in an in vitro preparation of the ventral nerve cord. Paired intracellular recordings were used to test the hypothesis that reciprocal inhibitory connections between levator (Lev) and depressor (Dep) MNs are direct. The injection of depolarising current into a Lev MN induces a hyperpolarising response in the Dep MN. This inhibitory relationship does not require spikes in the presynaptic MN, because it persists when spikes are suppressed by the sodium channel blocker tetrodotoxin (TTX). This reciprocal inhibition is graded, and both the amplitude and the time constant of the hyperpolarising response increase with increasing amount of depolarising current injected into an antagonistic MN. Although this inhibition is slow (synaptic delay around 10 ms), it is probably supported by a direct glutamatergic synapse from the antagonistic glutamatergic MN because it persists in the presence of the gamma-amino-butyric acid (GABA) synthesis inhibitor 3-mercapto-propionic acid (3-MPA). This hypothesis is reinforced by the demonstration of close appositions between antagonistic MNs by using a confocal microscope, and by the presence of glutamate-immunoreactive synapses on the neurites of MNs labelled for electron microscopy by intracellular injection of horseradish peroxidase.
在克氏原螯虾腹神经索的体外制备物中，研究了控制其第二腿关节的两组拮抗运动神经元（MNs）之间的抑制关系。采用配对细胞内记录来检验提肌（Lev）和降肌（Dep）运动神经元之间的相互抑制性连接是直接连接这一假设。向提肌运动神经元注入去极化电流会在降肌运动神经元中诱发超极化反应。这种抑制关系并不需要突触前运动神经元产生动作电位，因为当动作电位被钠通道阻滞剂河豚毒素（TTX）抑制时，这种抑制关系仍然存在。这种相互抑制是分级的，并且超极化反应的幅度和时间常数都随着注入拮抗运动神经元的去极化电流量的增加而增加。尽管这种抑制作用较慢（突触延迟约10毫秒），但它可能由来自拮抗谷氨酸能运动神经元的直接谷氨酸能突触支持，因为在γ-氨基丁酸（GABA）合成抑制剂3-巯基丙酸（3-MPA）存在的情况下，这种抑制作用仍然存在。通过使用共聚焦显微镜证明拮抗运动神经元之间紧密相邻，以及通过细胞内注射辣根过氧化物酶标记用于电子显微镜观察的运动神经元神经突上存在谷氨酸免疫反应性突触，这一假设得到了进一步加强。
