Pasic T R, Moore D R, Rubel E W
Virginia Merrill Bloedel Hearing Research Center, University of Washington School of Medicine, Seattle 98195.
J Comp Neurol. 1994 Oct 1;348(1):111-20. doi: 10.1002/cne.903480106.
Activity-dependent transneuronal regulation of neuronal soma size has been studied in the medial nucleus of the trapezoid body and ventral cochlear nucleus of adolescent gerbils. Cochlear ablation or tetrodotoxin has been used to eliminate afferent electrical activity in auditory nerve fibers permanently or for 24 or 48 hours. Previous studies have shown that the cross-sectional area of spherical cell somata in the ipsilateral anteroventral cochlear nucleus decreases within 24 hours of electrical activity blockade with tetrodotoxin, which is fully reversible when activity is restored. The present findings extend this work by directly comparing the results of unilateral blockade of auditory nerve action potentials or unilateral cochlear ablation on the size of spherical and globular cell bodies in the ventral cochlear nucleus with changes produced by the same manipulations in third-order cells, principal neurons in the medial nucleus of the trapezoid body. Soma size in both ventral cochlear nucleus cell types decreases reliably by 24 hours after cochlear removal or eighth nerve activity blockade by tetrodotoxin. Soma size of neurons in the contralateral medial nucleus of the trapezoid body decreases 48 hours, but not 24 hours, after either manipulation. When activity in auditory nerve fibers is allowed to resume for 7 days following a 48-hour activity blockade, soma size fully recovers in the medial nucleus of the trapezoid body as well as in ventral cochlear nucleus neurons. We also report that the cross-sectional area of neuronal soma in the medial nucleus of the trapezoid body is larger in lateral regions of medial nucleus of the trapezoid body (low-frequency representation) than in the medial regions of the nucleus (high-frequency representation). We conclude that cell body size changes in brainstem auditory neurons are reversible and that the signals associated with the loss and subsequent recovery of soma size are activity related. However, the delayed effect of activity deprivation in the medial nucleus of the trapezoid body suggests that trophic substances released by afferent axons may contribute to the maintenance of anatomical characteristics.
在幼年沙鼠的梯形体内侧核和腹侧耳蜗核中，已经对神经元胞体大小的活动依赖性跨神经元调节进行了研究。耳蜗切除术或河豚毒素已被用于永久消除或在24或48小时内消除听神经纤维中的传入电活动。先前的研究表明，用河豚毒素阻断电活动24小时内，同侧前腹侧耳蜗核中球形细胞胞体的横截面积会减小，当活动恢复时，这种减小是完全可逆的。本研究结果通过直接比较单侧阻断听神经动作电位或单侧耳蜗切除术对腹侧耳蜗核中球形和球状细胞体大小的影响，以及三阶细胞（梯形体内侧核中的主神经元）中相同操作所产生的变化，扩展了这项工作。在耳蜗切除或用河豚毒素阻断第八神经活动24小时后，腹侧耳蜗核两种细胞类型的胞体大小均可靠地减小。在任何一种操作后，对侧梯形体内侧核中神经元的胞体大小在48小时时减小，但在24小时时未减小。在48小时的活动阻断后，当听神经纤维的活动恢复7天时，梯形体内侧核以及腹侧耳蜗核神经元的胞体大小完全恢复。我们还报告称，梯形体内侧核外侧区域（低频代表区）的神经元胞体横截面积大于内侧区域（高频代表区）。我们得出结论，脑干听觉神经元的细胞体大小变化是可逆的，并且与胞体大小丧失及随后恢复相关的信号与活动有关。然而，梯形体内侧核中活动剥夺的延迟效应表明，传入轴突释放的营养物质可能有助于维持解剖学特征。
