Wadell I, Johansson H, Sjölander P, Sojka P, Djupsjöbacka M, Niechaj A
Department of Physiology, University of Umeå, Sweden.
J Physiol (Paris). 1991;85(4):223-34.
The purpose of this study was to investigate secondary muscle spindle afferents from the triceps-plantaris (GS) and posterior biceps and semitendinosus (PBSt) muscles with respect to their fusimotor reflex control from different types of peripheral nerves and receptors. The activity of single secondary muscle spindle afferents was recorded from dissected and cut dorsal root filaments in alpha-chloralose anaesthetized cats. Both single spindle afferents and sets of simultaneously recorded units (2-3) were investigated. The modulation and mean rate of firing of the afferent response to sinusoidal stretching of the GS and PBSts muscle were determined. Control measurements were performed in the absence of any reflex stimulation, while test measurements were made during reflex stimulation. The reflex stimuli consisted of manually performed movements of the contralateral hind limb, muscle stretches, ligament tractions and electrical stimulations of cutaneous afferents. Altogether 21 secondary spindle afferents were investigated and 20 different reflex stimuli were employed. The general responsiveness (i.e. number of significant reflex effects/number of control-test series) was 52.4%, but a considerable variation between different stimuli was found, with the highest (89.9%) for contralateral whole limb extension and the lowest (25.0%) for stretch of the contralateral GS muscle. The size of the response to a given stimulus varied considerably between different afferents, and, in the same afferent, different reflex stimuli produced effects of varying size. Most responses were characterized by an increase in mean rate of discharge combined with a decrease in modulation, indicative of static fusimotor drive (Cussons et al., 1977). Since the secondary muscle spindle afferents are part of a positive feedback loop, projecting back to both static and dynamic fusimotor neurones (Appelberg Et al., 1892 a, 1983 b; Appelberg et al., 1986), it is suggested that the activity in the loop may work like an amplified which, during some circumstances, enhance the effect of other reflex inputs to the system (Johansson et al., 1991 b).
本研究的目的是研究来自跖肌（GS）以及肱二头肌和半腱肌后部（PBSt）的次级肌梭传入纤维，了解它们在不同类型的外周神经和感受器的融合运动反射控制方面的情况。在α-氯醛糖麻醉的猫中，从解剖并切断的背根细丝记录单个次级肌梭传入纤维的活动。对单个肌梭传入纤维以及同时记录的一组单元（2 - 3个）进行了研究。测定了GS和PBSts肌肉正弦拉伸时传入反应的调制和平均放电率。在没有任何反射刺激的情况下进行对照测量，而在反射刺激期间进行测试测量。反射刺激包括对侧后肢的手动运动、肌肉拉伸、韧带牵引以及皮肤传入纤维的电刺激。总共研究了21个次级肌梭传入纤维，并采用了20种不同的反射刺激。总体反应性（即显著反射效应的数量/对照 - 测试系列的数量）为52.4%，但发现不同刺激之间存在相当大的差异，对侧全肢伸展时最高（89.9%），对侧GS肌肉拉伸时最低（25.0%）。对给定刺激的反应大小在不同传入纤维之间差异很大，并且在同一传入纤维中，不同的反射刺激产生不同大小的效应。大多数反应的特征是平均放电率增加，同时调制减少，这表明存在静态融合运动驱动（Cussons等人，1977）。由于次级肌梭传入纤维是正反馈回路的一部分，会反馈到静态和动态融合运动神经元（Appelberg等人，1982a，1983b；Appelberg等人，1986），因此有人提出，该回路中的活动可能起放大器的作用，在某些情况下会增强系统中其他反射输入的效果（Johansson等人，1991b）。
