Medullary reticulospinal tract mediating the generalized motor inhibition in cats: II. Functional organization within the medullary reticular formation with respect to postsynaptic inhibition of forelimb and hindlimb motoneurons
Medullary reticulospinal tract mediating the generalized motor inhibition in cats: II. Functional organization within the medullary reticular formation with respect to postsynaptic inhibition of forelimb and hindlimb motoneurons
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DOI：
10.1016/s0306-4522(02)00149-5
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发表时间：
2002-01-01
期刊：
影响因子：
3.3
通讯作者：
Sakamoto, T
中科院分区：
文献类型：
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作者：
Habaguchi, T;Takakusaki, K;Sakamoto, T
我们比较了在刺激去大脑猫的髓质网状结构引起的全身运动抑制过程中对前肢运动神经元和后肢运动神经元的突触后抑制作用。在这里，我们解决两个问题。首先，髓质对前肢运动神经元的抑制作用是否与对后肢运动神经元的抑制作用相当。其次，在与运动神经元的抑制连接方面，髓质网状结构内是否存在体形组织。传递到背内侧髓质网状结构的重复刺激（20-50 muA，50-100 Hz）可抑制前肢和后肢的双侧肌张力。髓质刺激使前肢（5.4 +/- 1.8 mV，n = 46）和后肢（5.4 +/- 2.0 mV，n = 59）运动神经元的膜电位超极化，同时输入电阻降低。前肢和后肢运动神经元的膜超极化和输入阻力程度没有差异。髓质刺激还抑制了运动神经元产生逆向和顺向尖峰的能力。对髓质抑制区域施加脉冲序列（一到三个脉冲，间隔 5-10 毫秒，20-50 muA）的刺激在运动神经元中诱导了兴奋性和抑制性突触后电位的混合。最值得注意的电位是具有晚期潜伏期的抑制性突触后电位。在大多数前肢（n = 57/58，98.3％）和后肢（n = 63/64，98.4％）运动神经元中观察到它们。前肢运动神经元的抑制电位的潜伏期为25-30 ms，峰值潜伏期为35-40 ms，后肢运动神经元的抑制电位的潜伏期为30-35 ms，峰值潜伏期为50-60 ms。在前肢和后肢运动神经元中引起抑制作用的有效位点的位置上没有观察到差异。这些位点均匀分布在髓质网状结构的背内侧部分，对应于巨细胞网状核的位置。从这些发现我们表明，在髓质诱导的广义运动抑制过程中，对前肢和后肢运动神经元施加了等量的突触后抑制作用。此外，就与前肢和后肢运动神经元的髓质网状脊髓抑制连接而言，髓质网状结构可以在功能上组织为同质或非特异性区域。 (C) 2002 国际广播组织。由爱思唯尔科学有限公司出版。保留所有权利。
We compared postsynaptic inhibitory effects on forelimb motoneurons and those on hindlimb motoneurons during generalized motor inhibition evoked by stimulating the medullary reticular formation in decerebrate cats. Here, we address two questions. First, whether the medullary inhibitory effects upon forelimb motoneurons are equivalent to those upon hindlimb motoneurons. Second, whether there is a somatotopographical organization within the medullary reticular formation in terms of inhibitory connections with motoneurons. Repetitive stimulation (20-50 muA, 50-100 Hz) delivered to the dorsomedial medullary reticular formation bilaterally suppressed muscle tone of both the forelimbs and hindlimbs. The medullary stimulation hyperpolarized the membrane potentials of the forelimb (5.4 +/- 1.8 mV, n = 46) and hindlimb (5.4 +/- 2.0 mV, n = 59) motoneurons together with a decrease in input resistance. The degree of membrane hyperpolarization and input resistance was not different in the forelimb and hindlimb motoneurons. The medullary stimulation also depressed the capability of generating antidromic and orthodromic spikes in the motoneurons. Stimuli with pulse trains (one to three pulses, 5-10-ms intervals, 20-50 muA) applied to the medullary inhibitory region induced a mixture of excitatory and inhibitory postsynaptic potentials in the motoneurons. The most noteworthy potentials were the inhibitory postsynaptic potentials with a late latency. They were observed in most forelimb (n = 57/58, 98.3%) and hindlimb (n = 63/64, 98.4%) motoneurons. The inhibitory potentials in forelimb motoneurons had a latency of 25-30 ms and a peak latency of 35-40 ms, and those in hindlimb motoneurons had a latency of 30-35 ms and a peak latency of 50-60 ms. A difference was not observed in the location of the effective sites for evoking the inhibitory effects in the forelimb and hindlimb motoneurons. These sites were homogeneously distributed in the dorsomedial part of the medullary reticular formation corresponding to the location of the nucleus reticularis gigantocellularis.From these findings we suggest that there is an equivalent amount of the postsynaptic inhibitory effects exerted on forelimb and hindlimb motoneurons during medullary-induced generalized motor inhibition. In addition, the medullary reticular formation may be functionally organized as a homogeneous or non-specific region in terms of the medullary reticulospinal inhibitory connections with forelimb and hindlimb motoneurons. (C) 2002 IBRO. Published by Elsevier Science Ltd. All rights reserved.