Grothe B, Schweizer H, Pollak G D, Schuller G, Rosemann C
Zoologisches Institut, Universität München, Germany.
J Comp Neurol. 1994 May 22;343(4):630-46. doi: 10.1002/cne.903430412.
The superior olivary complex (SOC) is the first station in the ascending auditory pathway that receives binaural projections. Two of the principal nuclei, the lateral superior olive (LSO) and the medial superior olive (MSO), are major sources of ascending projections to the inferior colliculus. Whereas almost all mammals have an LSO, it has traditionally been thought that only animals that hear low frequencies have an MSO. Recent reports, however, suggest that the medial part of the SOC in bats is highly variable and that at least some bats have a well-developed MSO. Thus, the main goal of this study was to evaluate the cytoarchitecture and connections of the principal superior olivary nuclei of the Mexican free-tailed bat, with specific attention directed at the MSO. Cell and fiber stained material revealed that the LSO and the medial nucleus of the trapezoid body (MNTB) are similar to those described for other mammals. There are two medial nuclei we refer to as dorsomedial periolivary nucleus (DMPO) and MSO. Tracer experiments exhibited that the DMPO receives bilateral projections from the cochlear nucleus, and additional projections from the ipsilateral MNTB. The DMPO sends a strong projection to the ipsilateral inferior colliculus. Positive staining for acetylcholinesterase indicates that the DMPO is a part of the olivocochlear system, as it is in other animals. The MSO in the free-tailed bat meets many of the criteria that traditionally define this nucleus. These include the presence of bipolar and multipolar principal cells, bilateral innervation from the cochlear nucleus, a strong projection from the ipsilateral MNTB, and the absence of cholinergic cells. The major difference from traditional MSO features is that it projects bilaterally to the inferior colliculus. Approximately 30% of its cells provide collateral projections to the colliculi on both sides. Functional implications of the MSO for the free-tailed bat are considered in the Discussion.
上橄榄复合体（SOC）是听觉上行通路中接收双耳投射的第一站。两个主要核团，即外侧上橄榄核（LSO）和内侧上橄榄核（MSO），是向下丘发出上行投射的主要来源。几乎所有哺乳动物都有LSO，传统观点认为只有能听到低频声音的动物才有MSO。然而，最近的报告表明，蝙蝠SOC的内侧部分变化很大，至少有些蝙蝠有发育良好的MSO。因此，本研究的主要目的是评估墨西哥无尾蝠主要上橄榄核的细胞结构和连接，特别关注MSO。细胞和纤维染色材料显示，LSO和梯形体内侧核（MNTB）与其他哺乳动物中描述的相似。有两个内侧核，我们将其称为背内侧橄榄周核（DMPO）和MSO。示踪实验表明，DMPO接受来自耳蜗核的双侧投射，以及来自同侧MNTB的额外投射。DMPO向同侧下丘发出强烈投射。乙酰胆碱酯酶阳性染色表明，DMPO是橄榄耳蜗系统的一部分，就像在其他动物中一样。无尾蝠的MSO符合传统上定义该核团的许多标准。这些标准包括存在双极和多极主细胞、来自耳蜗核的双侧神经支配、来自同侧MNTB的强烈投射以及不存在胆碱能细胞。与传统MSO特征的主要区别在于它向双侧下丘投射。其约30%的细胞向两侧的下丘提供侧支投射。讨论部分考虑了MSO对无尾蝠的功能意义。
