LORENTE R DE NO R
J Gen Physiol. 1951 Nov;35(2):183-201. doi: 10.1085/jgp.35.2.183.
The Et class of fibers includes fibers of Gasser's d.r. C group. The fibers of the dorsal root are more sensitive to the effect of lack of sodium than are the fibers of the ventral root. In the two roots there is a gradient of sensitivity to the lack of sodium, which is such that in all the root fibers the sensitivity decreases with increasing distance from the spinal cord. The gradient continues in the trunk up to about 10 to 12 mm. peripheral to the trunk-roots margin. No comparable gradient of sensitivity to the lack of sodium has been observed in the rest of the nerve trunk. The gradient of sensitivity to the lack of sodium has no relationship to the anatomical distribution of the epineurium. As a working hypothesis it is suggested that the gradient of sensitivity to the lack of sodium is one aspect of a transitional gradient that serves to establish a gradual change between the properties that the axons have inside the spinal cord and the properties that they have inside the nerve trunks. Details are given of the temporal course of the loss of excitability by root fibers deprived of sodium. It is suggested that sodium is present in the nerve fibers, in 2 forms, loosely and tightly bound sodium and that loss of loosely bound sodium is sufficient to render the nerve fibers unable to conduct impulses. If the rate of loss of loosely bound sodium is decreased, conversion of tightly bound into loosely bound sodium may temporarily restore the excitability of the nerve fibers.
Et类纤维包括加塞器背根C组纤维。背根纤维对缺钠效应的敏感性高于腹根纤维。在这两根神经根中，存在对缺钠的敏感性梯度，即在所有神经根纤维中，敏感性随着与脊髓距离的增加而降低。这种梯度在神经干中一直持续到距神经根边缘约10至12毫米处。在神经干的其余部分未观察到类似的对缺钠的敏感性梯度。对缺钠的敏感性梯度与神经外膜的解剖分布无关。作为一个工作假设，有人提出对缺钠的敏感性梯度是过渡梯度的一个方面，该过渡梯度用于在轴突在脊髓内的特性和它们在神经干内的特性之间建立逐渐变化。文中给出了缺钠的神经根纤维兴奋性丧失的时间进程的详细情况。有人提出钠以两种形式存在于神经纤维中，即松散结合的钠和紧密结合的钠，并且松散结合的钠的丧失足以使神经纤维无法传导冲动。如果松散结合的钠的丧失速率降低，紧密结合的钠向松散结合的钠的转化可能会暂时恢复神经纤维的兴奋性。
