Role of glycinergic inhibition in shaping activity of saccadic burst neurons.
Role of glycinergic inhibition in shaping activity of saccadic burst neurons.
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甘氨酸抑制在扫视爆发神经元活动形成中的作用。
DOI：
10.1152/jn.90565.2008
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发表时间：
2009
影响因子：
2.5
通讯作者：
H. Shimazu
中科院分区：
文献类型：
--
作者：
Y. Iwamoto;H. Kaneko;Kaoru Yoshida;H. Shimazu
跳眼的即时运动前信号是在中铅爆发神经元（MLBNs）水平上产生的。在固定期间，MLBNs受到全顶神经元（OPNs）的强直抑制，后者使用甘氨酸作为神经递质。为了阐明这种抑制的作用，我们研究了警惕性猫在离子吸附应用士的宁（一种甘氨酸受体拮抗剂）后水平mlbn的放电模式。三桶微移液用于细胞外记录和离子电泳。施用士的宁后，MLBNs在眼间间隔表现出自发放电和视觉反应。单脉冲刺激对侧上丘（SC）可诱发尖刺。这些结果表明，mlbn在跳间间隙接受大量兴奋性输入，并且opn的抑制作用确实是防止mlbn放电所必需的。士的宁也影响MLBNs的眼跳相关活性。与正常情况下一样，这种活动的爆发在扫视结束前迅速下降，但随后是低频率的尖峰活动，这种活动持续到扫视结束后。这表明，在正常情况下，扫视的终止是由opn的抑制作用恢复决定的，而不是由mlbn兴奋性输入的终止决定的。此外，施用士的宁后，扫视期间的放电速率和峰值数量增加，表明mlbn也受到非opn来源的甘氨酸能抑制。我们得出结论，甘氨酸能抑制在维持稳定固定、眼跳终止以及调节眼跳大小和速度方面起着重要作用。
The immediate premotor signals for saccades are created at the level of medium-lead burst neurons (MLBNs). During fixations, MLBNs receive tonic inhibition from omnipause neurons (OPNs), which use glycine as a neurotransmitter. To elucidate the role of this inhibition, we studied discharge patterns of horizontal MLBNs following iontophoretic application of strychnine, a glycine-receptor antagonist, in alert cats. Three-barrel micropipettes were used for extracellular recording and iontophoresis. After application of strychnine, MLBNs exhibited spontaneous discharge and visual responses during intersaccadic intervals. Spikes were evoked by single-pulse stimulation of the contralateral superior colliculus (SC). These results show that MLBNs receive substantial excitatory input during intersaccadic intervals and that inhibitory action of OPNs is indeed necessary to prevent MLBNs from firing. Strychnine also affected saccade-related activity of MLBNs. The burst of activity, as in normal conditions, declined rapidly before the end of saccades but was followed by low rate spike activity, which continued beyond the end of saccades. This suggests that in normal conditions, the termination of saccades is determined by resumed inhibitory action of OPNs and not by termination of excitatory input to MLBNs. In addition, the firing rate and the number of spikes during saccades increased after strychnine application, suggesting that MLBNs receive glycinergic inhibition of non-OPN origin as well. We conclude that glycinergic inhibition plays essential roles in the maintenance of stable fixation, the termination of saccades, and the regulation of saccade size and velocity.