Kiemel T, Cohen A H
Department of Biology, University of Maryland, College Park, MD 20742, USA.
Brain Res. 2001 May 4;900(1):57-64. doi: 10.1016/s0006-8993(01)02244-2.
It is well known that rhythmic lateral bending of the isolated lamprey spinal cord/notochord can entrain the central pattern generator (CPG) for locomotion. During entrainment, the CPG's frequency is equal to the bending frequency. We report here that bending can also have a slowly-decaying excitatory effect on the CPG's frequency. Experiments were performed in which the caudal end of a 30-50 segment piece of spinal cord/notochord was repeatedly rhythmically bent for 0.5-12 cycles. A slowly-decaying excitation was said to be present if after the termination of bending the CPG's frequency was significantly greater than baseline and decayed back to baseline with a time constant of one or more cycles. In 14 of 16 animals, a slowly-decaying excitation could be evoked by bending. In five of the nine animals tested, this slowly-decaying excitation could be evoked with bending frequencies both faster and slower than the baseline frequency. Depending on the animal, the slowly-decaying excitation could be elicited by as little as one-half cycle of bending and by bending amplitudes as small as 6-21 degrees peak deflection. We interpret these data as evidence of a second effect of bending distinct from the phase-dependent effect that produces entrainment.
众所周知，对分离的七鳃鳗脊髓/脊索进行有节奏的侧向弯曲能够带动用于运动的中枢模式发生器（CPG）。在带动过程中，CPG的频率等于弯曲频率。我们在此报告，弯曲对CPG的频率也可产生缓慢衰减的兴奋作用。进行了如下实验：对一段包含30 - 50节段的脊髓/脊索的尾端进行0.5 - 12个周期的反复有节奏弯曲。如果在弯曲终止后CPG的频率显著高于基线水平，并以一个或多个周期的时间常数衰减回到基线水平，则认为存在缓慢衰减的兴奋作用。在16只动物中的14只中，弯曲可诱发缓慢衰减的兴奋作用。在接受测试的9只动物中的5只中，弯曲频率高于和低于基线频率时均可诱发这种缓慢衰减的兴奋作用。根据不同动物的情况，只需半个周期的弯曲以及小至6 - 21度峰-峰偏转的弯曲幅度即可诱发缓慢衰减的兴奋作用。我们将这些数据解释为弯曲的第二种作用的证据，该作用不同于产生带动的相位依赖性作用。
