Gregory J E, Morgan D L, Proske U
J Neurophysiol. 1985 Dec;54(6):1383-95. doi: 10.1152/jn.1985.54.6.1383.
A continuing controversy surrounds the question of whether Golgi tendon organs are examples of receptors in which impulses may be generated at more than one site. This paper reports a systematic examination of a number of models incorporating single or multiple impulse generators and of the compatibility of their predictions with experimental observations. Two phenomena, in particular, that must be accounted for are nonlinear summation and cross-adaptation. When two motor units each with a direct effect on the tendon organ are stimulated together, the rate of discharge is greater than either individual rate but is less than their sum. In cross-adaptation a conditioning response elicited by one motor unit contraction produces adaptation of the discharge associated with stimulation of a second motor unit. A model with a central impulse generator can be modified to account for nonlinear summation by postulating a nonlinear transformation in the generator current-to-impulse rate conversion. Experiments measuring summation of responses to stimulation of three inputs produced results that did not support this model. Another variation of the model, which had a nonlinearity in the tension-to-current step and cross-connections (mechanical or neural) between tendon strands stressed by contracting muscle fibers, was able to account for the observations. A second model that provided the right predictions was a multiple impulse generator with cross-connections. Which of the two models best fits the experimental observations can be decided by comparing the calculated summation coefficients and cross-adaptation coefficients. A central impulse generator predicts a negative correlation, the multiple impulse generator a positive correlation. All of the observations were made using tendon organs of cat soleus muscle. Responses were recorded to stimulation of filaments of ventral root. In a comparison between 20 pairs of responses from six tendon organs the correlation between summation and cross-adaptation coefficients was found to be significantly positive. We conclude that the tendon organ model that accurately predicts all of the experimental observations incorporates multiple generators.
围绕高尔基腱器官是否属于冲动可在多个部位产生的感受器这一问题，一直存在争议。本文报告了对一些包含单个或多个冲动发生器的模型进行的系统研究，以及它们的预测与实验观察结果的兼容性。特别需要解释的两种现象是非线性总和与交叉适应。当同时刺激两个对腱器官有直接作用的运动单位时，放电频率大于单个运动单位的放电频率，但小于两者之和。在交叉适应中，一个运动单位收缩引发的条件反应会使与第二个运动单位刺激相关的放电产生适应。一个具有中央冲动发生器的模型可以通过假设发生器电流到冲动频率转换中的非线性变换来修正，以解释非线性总和。测量对三个输入刺激的反应总和的实验结果并不支持该模型。该模型的另一种变体，在张力到电流的转换步骤中存在非线性，并且在收缩的肌肉纤维所牵拉的腱束之间存在交叉连接（机械或神经连接），能够解释这些观察结果。另一个能做出正确预测的模型是具有交叉连接的多个冲动发生器。通过比较计算出的总和系数和交叉适应系数，可以确定这两个模型中哪一个最符合实验观察结果。中央冲动发生器预测为负相关，多个冲动发生器预测为正相关。所有观察均使用猫比目鱼肌的腱器官进行。记录了对腹根细丝刺激的反应。在对六个腱器官的20对反应进行比较时，发现总和系数与交叉适应系数之间的相关性为显著正相关。我们得出结论，能够准确预测所有实验观察结果的腱器官模型包含多个发生器。
