Schäfer S S, Schoppmeyer M A
Department of Neurophysiology (4230), Medical School of Hannover, Germany.
Brain Res. 1996 Feb 12;709(1):111-21. doi: 10.1016/0006-8993(95)01319-9.
The responses of 46 Ia afferents from the tibial anterior muscle of the cat to repetitive ramp-and-hold stretches were investigated under a succinylcholine (SCh) infusion of 120 micrograms.kg-1.min-1 lasting 15 to 25 min. It was possible to distinguish four consecutive phases of the effect of the SCh on the responsiveness of the Ia afferents. The first three of these four phases have already been described. We analysed in more detail the changes from Phase III to the end of Phase IV. Static fusimotor effects were dominant in the discharge patterns obtained during Phase III; dynamic fusimotor effects prevail at the end of Phase IV. Our observations were quantified by comparing the mean values of initial activity, final static value, dynamic response and slow receptor adaptation read from the discharge patterns obtained during Phase III with the mean values of the same parameters obtained from discharge patterns from the end of Phase IV: the two mean values were significantly different for each of the four measurements. This change from Phase III to the end of Phase IV is highly specific for each spindle. To demonstrate this spindle specificity, discharge patterns were selected from among those produced by each Ia afferent in Phase III and at the end of Phase IV. Each of these discharge patterns was assigned to one of six categories. Category I displays purely dynamic fusimotor effects and Category VI purely static fusimotor effects. Categories II, IV and V display combinations of static and dynamic fusimotor effects with an increasing admixture of static fusimotor effects. The spindle-specific change from Phase III to the end of Phase IV is defined in terms of the specific degree of change from a higher-number to a lower-number category in the case of each of the 46 Ia afferents. In the discussion a combination of activity by the two nuclear bag fibres of a spindle is deduced from the specific discharge pattern of each category. The conclusion from these considerations is that results obtained from the administration of SCh have to be interpreted with great caution in making any statement about the existence of a dynamic bag1 fibre in a spindle.
在持续15至25分钟、琥珀酰胆碱（SCh）输注速率为120微克·千克⁻¹·分钟⁻¹的条件下，研究了猫胫骨前肌46条Ia类传入纤维对重复斜坡-保持拉伸的反应。可以区分SCh对Ia类传入纤维反应性影响的四个连续阶段。这四个阶段中的前三个阶段已经有过描述。我们更详细地分析了从第三阶段到第四阶段结束时的变化。在第三阶段获得的放电模式中，静态肌梭运动效应占主导；在第四阶段结束时，动态肌梭运动效应占主导。通过比较从第三阶段获得的放电模式中读取的初始活动、最终静态值、动态反应和慢感受器适应的平均值，与从第四阶段结束时的放电模式中获得的相同参数的平均值，对我们的观察结果进行了量化：对于这四项测量中的每一项，两个平均值都有显著差异。从第三阶段到第四阶段结束的这种变化对每个肌梭来说是高度特异性的。为了证明这种肌梭特异性，从每个Ia类传入纤维在第三阶段和第四阶段结束时产生的放电模式中进行选择。这些放电模式中的每一个都被归入六个类别之一。第一类显示纯粹的动态肌梭运动效应，第六类显示纯粹的静态肌梭运动效应。第二、四和五类显示静态和动态肌梭运动效应的组合，且静态肌梭运动效应的混合比例逐渐增加。从第三阶段到第四阶段结束的肌梭特异性变化是根据46条Ia类传入纤维中每一条从较高编号类别到较低编号类别的特定变化程度来定义的。在讨论中，从每个类别的特定放电模式推断出一个肌梭的两条核袋纤维的活动组合。从这些考虑得出的结论是，在对肌梭中动态袋1纤维的存在做出任何陈述时，必须非常谨慎地解释给予SCh所获得的结果。
