Ryan A F, Keithley E M, Wang Z X, Schwartz I R
Department of Surgery/Otolaryngology, UCSD School of Medicine, La Jolla 92093.
J Comp Neurol. 1990 Oct 22;300(4):572-82. doi: 10.1002/cne.903000410.
Two populations of superior olivary neurons which project to different sensory cell regions in the cochlea also give off collateral projections to the ventral cochlear nucleus (VCN) and adjacent brainstem. To determine whether these VCN projections also have different targets they were characterized by selective retrograde amino acid transport. Retrograde transport of 3H-d-aspartate (D-ASP) selectively labeled the unmyelinated fibers and neurons of the lateral olivocochlear (OC) system including a dense collateral projection to the central VCN. Retrograde transport of 3H-nipecotic acid (NIP) labeled the myelinated fibers and neurons of the medial OC system, including collateral projections to the peripheral VCN, subpeduncular granule cells, and nucleus Y. Medial and lateral OC efferent collaterals thus innervate different regions of the CN. Lateral system collaterals overlap extensively with Type I spiral ganglion cell afferent input. They are well positioned to play a role in modulating afferent input to the central auditory system, as is the primary projection of these efferents to the cochlea. The medial system collaterals project near the recently described afferent projections of Type II spiral ganglion cells. The medial system collaterals may therefore be related to the function of outer hair cells, as the medial system primary axons appear to be in the cochlea.
投射到耳蜗不同感觉细胞区域的两群上橄榄神经元也向蜗腹侧核（VCN）和邻近脑干发出侧支投射。为了确定这些向VCN的投射是否也有不同的靶点，通过选择性逆行氨基酸转运对它们进行了特征描述。3H-D-天冬氨酸（D-ASP）的逆行转运选择性地标记了外侧橄榄耳蜗（OC）系统的无髓纤维和神经元，包括向VCN中央的密集侧支投射。3H-哌啶酸（NIP）的逆行转运标记了内侧OC系统的有髓纤维和神经元，包括向VCN外周、脚周颗粒细胞和Y核的侧支投射。因此，内侧和外侧OC传出侧支支配着蜗神经核的不同区域。外侧系统侧支与I型螺旋神经节细胞传入输入广泛重叠。它们处于很好的位置来调节向中枢听觉系统的传入输入，就像这些传出纤维向耳蜗的主要投射一样。内侧系统侧支投射到最近描述的II型螺旋神经节细胞的传入投射附近。因此，内侧系统侧支可能与外毛细胞的功能有关，因为内侧系统的初级轴突似乎位于耳蜗中。
