McClellan A D, Sigvardt K A
Department of Physiology and Biophysics, University of Iowa, Iowa City 52242.
J Neurosci. 1988 Jan;8(1):133-45. doi: 10.1523/JNEUROSCI.08-01-00133.1988.
The in vitro lamprey spinal cord contains a "central pattern generator" (CPG) that can generate locomotor activity with excitatory amino acids added to the bath. The motor pattern can be entrained by imposed rhythmic bending of either the caudal or rostral end of the notochord/spinal cord. In the present study, the quantitative and mechanistic features of entrainment were investigated. Increasing the amplitude of the imposed movement increased the range of frequencies over which entrainment occurred. Brief, pulsed, imposed movements could reset the locomotor rhythm. During entrainment at different imposed movement frequencies, the burst duration was a constant proportion of about 35% of the cycle time. The intersegmental phase lag, which is usually constant at about 0.01 during locomotion, decreased significantly with caudal imposed movements. A small increase in the phase lags was observed with rostral imposed movements. In low-calcium Ringer's, briefly bending the notochord/spinal cord activated intraspinal mechanoreceptors and elicited ascending and descending unit activity in lateral spinal fascicles many segments from the point of bending. However, this ascending or descending movement-related activity was insufficient to fully entrain the locomotor rhythm, since blocking the pattern in the region of bending abolished 1:1 entrainment. The mechanoreceptors appear to act locally on the CPG networks, since interrupting the ascending or descending movement-related activity with lesions of the lateral fascicles did not abolish entrainment. In contrast, stripping the very lateral margins of the spinal cord in the region of bending did abolish entrainment, presumably by destroying the transduction region of the mechanoreceptors. The data, taken together, suggest that the mechanoreceptors entrain the local CPG networks, and this timing information is then distributed to the other parts of the spinal motor networks through the coordinating system.
体外七鳃鳗脊髓包含一个“中枢模式发生器”（CPG），在浴槽中添加兴奋性氨基酸时，该发生器可产生运动活性。运动模式可通过对脊索/脊髓尾端或头端施加有节奏的弯曲来诱导。在本研究中，对诱导的定量和机制特征进行了研究。增加施加运动的幅度会增加发生诱导的频率范围。短暂的、脉冲式的施加运动可重置运动节律。在不同的施加运动频率下进行诱导时，爆发持续时间约占周期时间的35%，保持恒定比例。节段间相位滞后在运动过程中通常恒定在约0.01，随着尾端施加运动而显著减小。随着头端施加运动，观察到相位滞后略有增加。在低钙林格氏液中，短暂弯曲脊索/脊髓会激活脊髓内的机械感受器，并在距弯曲点多个节段的外侧脊髓束中引发上行和下行单位活动。然而，这种与上升或下降运动相关的活动不足以完全诱导运动节律，因为阻断弯曲区域的模式会消除1:1诱导。机械感受器似乎在局部作用于CPG网络，因为用外侧束损伤中断与上升或下降运动相关的活动并不会消除诱导。相比之下，在弯曲区域剥离脊髓的最外侧边缘确实会消除诱导，推测是通过破坏机械感受器的转导区域。综合这些数据表明，机械感受器诱导局部CPG网络，然后这种时间信息通过协调系统分布到脊髓运动网络的其他部分。
