Schäfer S S, Berkelmann B, Dadfar F
Department of Neurophysiology (OE 4230), Hannover Medical School, D-30625 Hannover, Germany.
J Neurophysiol. 2003 Apr;89(4):1748-60. doi: 10.1152/jn.00952.2002.
Under static gamma stimulations, Ia afferents may discharge in a highly irregular way or may be driven. However, the genesis of the highly irregular form of discharge is unclear. We offer an interpretation of irregular discharge behavior. Twenty-three primary (Ia) muscle spindle afferents from the tibial anterior muscle of the cat were subjected to static gamma stimulation, the stimulation frequency increasing linearly from 2 to 110/s. In addition, 17 of the spindle afferents were subjected to two different prestretch values of the muscle while the static gamma fiber was now subjected to constant frequency stimulation at five different stimulation frequencies ranging from 9.4 to 95/s. The responses of the Ia afferents to the static gamma stimulation were presented through discharge patterns that were constructed by the frequencygram method and were subjected to computer analysis, by means of which the Ia responses were evaluated quantitatively. Two groups of static gamma stimulations were identified. The first group of gamma stimulations leads in the Ia response to highly irregular discharging within a broad discharge band. This highly irregular discharging resolves into regular oscillatory responses of large magnitude occurring in the rhythm of the gamma stimuli. According to this observation, the highly irregular discharges result from the fact that the Ia afferent generates more than one action potential per gamma stimulus. The second group of gamma stimulation leads in the Ia response either to driving of the action potentials in the rhythm of the gamma stimulation frequency or of submultiples of it or to irregular discharging within a smaller discharge band. Under the two latter conditions, oscillatory Ia responses of small magnitude occurring in the rhythm of the gamma stimuli are proved to be generated by the Ia afferents. The results are explained in terms of the strength of contraction of the polar parts and the resulting stretch of the sensory parts of the intrafusal muscle fibers that are responsible.
在静态γ刺激下，Ia传入纤维可能以高度不规则的方式放电，也可能被驱动。然而，这种高度不规则放电形式的起源尚不清楚。我们对不规则放电行为提出一种解释。对来自猫胫前肌的23条初级（Ia）肌梭传入纤维施加静态γ刺激，刺激频率从2/s线性增加到110/s。此外，在对静态γ纤维施加9.4至95/s五个不同刺激频率的恒定频率刺激时，对其中17条肌梭传入纤维施加两种不同的肌肉预拉伸值。Ia传入纤维对静态γ刺激的反应通过频率图法构建的放电模式呈现，并进行计算机分析，借此对Ia反应进行定量评估。确定了两组静态γ刺激。第一组γ刺激导致Ia反应在较宽的放电范围内出现高度不规则放电。这种高度不规则放电分解为以γ刺激节律出现的大幅度规则振荡反应。根据这一观察结果，高度不规则放电是由于Ia传入纤维在每个γ刺激下产生多个动作电位。第二组γ刺激导致Ia反应要么以γ刺激频率或其分数频率的节律驱动动作电位，要么在较小的放电范围内不规则放电。在后两种情况下，已证明Ia传入纤维产生以γ刺激节律出现的小幅度振荡Ia反应。结果根据负责的梭内肌纤维极性部分的收缩强度以及由此产生的感觉部分的拉伸来解释。
