Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA.
J Neurophysiol. 2012 Jun;107(11):3168-80. doi: 10.1152/jn.01134.2011. Epub 2012 Mar 21.
Presynaptic inhibition is a powerful mechanism for selectively and dynamically gating sensory inputs entering the spinal cord. We investigated how hindlimb mechanics influence presynaptic inhibition during locomotion using pioneering approaches in an in vitro spinal cord-hindlimb preparation. We recorded lumbar dorsal root potentials to measure primary afferent depolarization-mediated presynaptic inhibition and compared their dependence on hindlimb endpoint forces, motor output, and joint kinematics. We found that stance-phase force on the opposite limb, particularly at toe contact, strongly influenced the magnitude and timing of afferent presynaptic inhibition in the swinging limb. Presynaptic inhibition increased in proportion to opposite limb force, as well as locomotor frequency. This form of presynaptic inhibition binds the sensorimotor states of the two limbs, adjusting sensory inflow to the swing limb based on forces generated by the stance limb. Functionally, it may serve to adjust swing-phase sensory transmission based on locomotor task, speed, and step-to-step environmental perturbations.
突触前抑制是一种强大的机制，可选择性地和动态地控制进入脊髓的感觉输入。我们使用体外脊髓-后肢准备中的开创性方法研究了后肢力学如何影响运动过程中的突触前抑制。我们记录了腰背部神经根电位，以测量初级传入去极化介导的突触前抑制，并比较了它们对后肢末端力、运动输出和关节运动学的依赖性。我们发现，对侧肢体的支撑相力，特别是在脚趾接触时，强烈影响摆动肢体的传入突触前抑制的幅度和时间。突触前抑制与对侧肢体的力以及运动频率成比例增加。这种形式的突触前抑制将两个肢体的感觉运动状态联系起来，根据支撑肢体产生的力来调整摆动肢体的感觉传入。从功能上讲，它可能有助于根据运动任务、速度和步与步的环境干扰来调整摆动阶段的感觉传递。
