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首页> 外文期刊>The European Journal of Neuroscience >Corticospinal control of antagonistic muscles in the cat
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Corticospinal control of antagonistic muscles in the cat

机译：皮质脊髓控制猫的拮抗肌肉

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We recently suggested that movement-related inter-joint muscle synergies are recruited by selected excitation and selected release from inhibition of cortical points. Here we asked whether a similar cortical mechanism operates in the functional linking of antagonistic muscles. To this end experiments were done on ketamine-anesthetized cats. Intracortical microstimulation (ICMS) and intramuscular electromyographic recordings were used to find and characterize wrist, elbow and shoulder antagonistic motor cortical points. Simultaneous ICMS applied at two cortical points, each evoking activity in one of a pair of antagonistic muscles, produced co-contraction of antagonistic muscle pairs. However, we found an obvious asymmetry in the strength of reciprocal inhibition; it was always significantly stronger on physiological extensors than flexors. Following intravenous injection of a single bolus of strychnine, a cortical point at which only a physiological flexor was previously activated also elicited simultaneous activation of its antagonist. This demonstrates that antagonistic corticospinal neurons are closely grouped, or intermingled. To test whether releasing a cortical point from inhibition allows it to be functionally linked with an antagonistic cortical point, one of three GABA_A receptor antagonists, bicuculline, gabazine or picrotoxin, was injected iontophoretically at one cortical point while stimulation was applied to an antagonistic cortical point. This coupling always resulted in co-contraction of the represented antagonistic muscles. Thus, antagonistic motor cortical points are linked by excitatory intracortical connections held in check by local GABAergic inhibition, with reciprocal inhibition occurring at the spinal level. Importantly, the asymmetry of cortically mediated reciprocal inhibition would appear significantly to bias muscle maps obtained by ICMS in favor of physiological flexors.
机译：我们最近建议，通过选择刺激和抑制皮质点释放来招募运动相关的关节间肌肉协同作用。在这里，我们问类似的皮质机制是否在拮抗肌肉的功能性连接中起作用。为此，在氯胺酮麻醉的猫上进行了实验。皮层内微刺激（ICMS）和肌内肌电图记录被用来发现和表征手腕，肘部和肩部拮抗运动皮质。在两个皮层点同时应用ICMS，每一个在一对拮抗性肌肉中的一个上引起活性，从而产生拮抗性肌肉对的共收缩。但是，我们发现相互抑制强度存在明显的不对称性。在生理伸肌上它总是比屈肌明显更强。静脉注射单剂量的士的宁后，先前仅激活生理屈肌的皮质点也引起了其拮抗剂的同时激活。这表明拮抗性皮质脊髓神经元紧密结合或混合在一起。为了测试释放皮质点是否从抑制中释放出来，使其能够与拮抗性皮质点功能性连接，在刺激作用于拮抗性皮质点的同时，通过离子电渗疗法在一个皮质点注射了三种GABA_A受体拮抗剂之一Bicuculline，gabazine或pictotoxin 。这种耦合总是导致所代表的拮抗肌共收缩。因此，拮抗运动皮层点通过局部GABA能抑制抑制的兴奋性皮层内连接相联系，而相互抑制发生在脊柱水平。重要的是，皮质介导的相互抑制的不对称性将显着偏向由ICMS获得的肌肉图，从而偏向生理屈肌。

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