Spontaneous bursting activity is already generated in the cochlea before hearing onset and represents an important condition of the functional and anatomical organization of auditory brainstem nuclei. In the present study, cochlea ablation induced changes were characterized in auditory brainstem nuclei indirectly innervated by auditory nerve fibers before hearing onset. In Meriones unguiculatus immunohistochemical labeling of calbindin-D28k (CB) and synaptophysin (SYN) were performed. The influence of cochlea-ablation on CB or SYN was analyzed by considering their differential immunoreaction during development.

During the normal postnatal development, CB was first detected in somata of the medial nucleus of the trapezoid body (MNTB) at postnatal day (P)4. The immunoreaction increased gradually in parallel to the appearance of CB-immunoreactive terminal fields in distinct superior olivary complex (SOC) nuclei. Cochlear removal at P5 or P9 in animals with 24 and 48 h survival times resulted in an increase in somatic CB-labeling in the lesioned MNTB including terminal fields compared to the non-lesioned MNTB.

SYN-immunolabeling was first detected at P0 and began to strongly encircle the MNTB neurons at P4. A further progression was observed with age. Cochlear ablation resulted in a significant reduction of SYN-labeled MNTB areas of P5-cochlea-ablated gerbils after 48 h post-lesion. In P9 cochlea-ablated gerbils, a redistribution of SYN-positive terminals was seen after 24 and 48 h. Taken together, the destruction of cochlea differentially influences CB- and SYN-labeling in the MNTB, which should be considered in association with different critical periods before hearing onset.

在听力开始之前，耳蜗中已经产生了自发的爆发活动，并且代表了听觉脑干核的功能和解剖组织的重要条件。在本研究中，耳蜗消融引起的变化在听力发作前由听神经纤维间接支配的听性脑干核中表征。在Meriones unguiculatus中，进行了钙结合蛋白-D28k (CB) 和突触素 (SYN) 的免疫组织化学标记。通过考虑它们在发育过程中的差异免疫反应来分析耳蜗消融对 CB 或 SYN 的影响。

在正常的出生后发育过程中，CB 首次在出生后第 4 天在梯形体内侧核 (MNTB) 的胞体中检测到。在明显的上橄榄复合体 (SOC) 核中，随着 CB 免疫反应性末端场的出现，免疫反应逐渐增加。与未损伤的 MNTB 相比，在具有 24 和 48 小时存活时间的动物中，在 P5 或 P9 处去除耳蜗导致损伤的 MNTB （包括终末场）中的体细胞 CB 标记增加。

SYN 免疫标记首先在 P0 检测到，并在 P4 开始强烈包围 MNTB 神经元。随着年龄的增长，观察到了进一步的进展。耳蜗消融导致 P5 耳蜗消融沙鼠的 SYN 标记的 MNTB 区域在损伤后 48 小时后显着减少。在 P9 耳蜗消融的沙鼠中，在 24 和 48 小时后观察到 SYN 阳性末端的重新分布。总之，耳蜗的破坏对 MNTB 中的 CB 和 SYN 标记有不同的影响，这应该与听力发作前的不同关键时期相关联。