Early postnatal development of GABAergic presynaptic inhibition of Ia proprioceptive afferent connections in mouse spinal cord.
Early postnatal development of GABAergic presynaptic inhibition of Ia proprioceptive afferent connections in mouse spinal cord.
复制标题
小鼠脊髓中 Ia 本体感觉传入连接的 GABA 能突触前抑制的出生后早期发育。
DOI：
10.1152/jn.00783.2012
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发表时间：
2013
影响因子：
2.5
通讯作者：
Ladle,DavidR
中科院分区：
文献类型：
--
作者：
Sonner,PatrickM;Ladle,DavidR
感觉反馈对于正常运动和适应运动过程中的外部扰动至关重要。 Ia 组传入神经提供的反馈通过单突触连接直接影响运动输出，并通过脊髓间神经元回路间接影响运动输出。例如，负责相互抑制的电路，其作用是防止拮抗屈肌和伸肌的共同收缩，由 Ia 传入反馈驱动。此外，介导突触前抑制的电路可以以特定任务的方式限制 Ia 传入突触传递到中枢神经元目标。这些回路也可以通过刺激本体感觉传入神经来激活。啮齿类动物的运动能力在出生后发育过程中迅速成熟；因此，我们分析了小鼠出生时交互和突触前抑制回路的功能状态，并将反应与出生后发育 1 周后的观察结果进行比较。使用来自分离和半切脊髓制剂的细胞外生理技术，我们证明Ia传入诱发的相互抑制在阻断出生时和出生后1周的拮抗性运动神经元激活方面同样有效。相比之下，出生时对肌肉神经传入神经的调节刺激未能引起足以阻止 Ia 传入神经和运动神经元之间突触功能传递的突触前抑制，尽管可以通过刺激邻近的背根来激发背根电位。然而，在出生后第一周结束时，很容易观察到该突触的突触前抑制。这些结果表明，从外周到中央脊髓回路的传入反馈在出生时仅被弱门控，这可能在出生后早期经历期间提供对外周反馈的增强的敏感性。
Sensory feedback is critical for normal locomotion and adaptation to external perturbations during movement. Feedback provided by group Ia afferents influences motor output both directly through monosynaptic connections and indirectly through spinal interneuronal circuits. For example, the circuit responsible for reciprocal inhibition, which acts to prevent co-contraction of antagonist flexor and extensor muscles, is driven by Ia afferent feedback. Additionally, circuits mediating presynaptic inhibition can limit Ia afferent synaptic transmission onto central neuronal targets in a task-specific manner. These circuits can also be activated by stimulation of proprioceptive afferents. Rodent locomotion rapidly matures during postnatal development; therefore, we assayed the functional status of reciprocal and presynaptic inhibitory circuits of mice at birth and compared responses with observations made after 1 wk of postnatal development. Using extracellular physiological techniques from isolated and hemisected spinal cord preparations, we demonstrate that Ia afferent-evoked reciprocal inhibition is as effective at blocking antagonist motor neuron activation at birth as at 1 wk postnatally. In contrast, at birth conditioning stimulation of muscle nerve afferents failed to evoke presynaptic inhibition sufficient to block functional transmission at synapses between Ia afferents and motor neurons, even though dorsal root potentials could be evoked by stimulating the neighboring dorsal root. Presynaptic inhibition at this synapse was readily observed, however, at the end of the first postnatal week. These results indicate Ia afferent feedback from the periphery to central spinal circuits is only weakly gated at birth, which may provide enhanced sensitivity to peripheral feedback during early postnatal experiences.