Matz S P
Institute of Neuroscience, University of Oregon, Eugene 97403, USA.
Brain Behav Evol. 1995;46(2):108-20. doi: 10.1159/000113263.
This report describes the connections of the olfactory bulb in juvenile chinook salmon (Oncorhynchus tshawytscha) as revealed by the retrograde and anterograde transport of biotinylated dextran amine (BDA). Pressure injections of BDA to discrete locations within the bulb reveal that the olfactory bulb projects via medial and lateral tracts to various regions of the dorsal and ventral telencephalon as well as to the diencephalon. Terminal-like boutons are present in the ventral, dorsal, lateral and supracommissural nuclei of the ventral telencephalon and in the lateral-ventral and posterior zones of the dorsal telencephalon. There is also a projection to the nucleus taenia and to the contralateral olfactory bulb. A diencephalic terminal field occurs in the posterior tuberal region of the ventral diencephalon. Olfactory bulb fibers in the preoptic region have axonal varicosities near neurons containing releasing hormones. A synaptic connection is suggested allowing for the possibility that output from the olfactory bulb may directly modulate the activity of these neurons. Telencephalic injections of BDA are used to determine the origins of olfactory bulb efferents. Neurons are retrogradely labeled by BDA in a Golgi-like manner, allowing one to visualize the morphology of olfactory bulb efferents. Three types of neurons in the bulb are filled by injections into the posterior zone of the dorsal telencephalon: mitral cells and ruffed cells in the external cellular layer, and neurons in the internal cellular layer. Although it has been known that both mitral cells and neurons in the internal cellular layer project out of the bulb in teleosts, the use of BDA allowed for an accurate description of the morphology of these extrinsically projecting neurons. This is the first evidence that the ruffed cells in salmon project out of the bulb. The results of this study suggest that the secondary olfactory projections in chinook salmon are consistent with those in other teleosts with minor variations. The data also show that olfactory bulb efferents originate not solely from mitral cells in the external cellular layer but also from ruffed cells in the external cellular layer and neurons in the internal cellular layer. It is proposed that the extrinsically projecting neurons in the internal cellular layer constitute an anterior olfactory nucleus in salmon.
本报告描述了通过生物素化葡聚糖胺（BDA）的逆行和顺行运输所揭示的幼年奇努克鲑鱼（Oncorhynchus tshawytscha）嗅球的连接情况。向嗅球内的不同位置进行BDA的压力注射显示，嗅球通过内侧和外侧束投射到背侧和腹侧端脑的各个区域以及间脑。终末样小体存在于腹侧端脑的腹侧、背侧、外侧和连合上核以及背侧端脑的外侧腹侧和后区。还有一条投射到带状核和对侧嗅球。间脑终末场出现在腹侧间脑的后结节区。视前区的嗅球纤维在含有释放激素的神经元附近有轴突膨体。这表明存在突触连接，嗅球的输出可能直接调节这些神经元的活动。向端脑注射BDA用于确定嗅球传出纤维的起源。神经元以类似高尔基染色的方式被BDA逆行标记，从而可以观察到嗅球传出纤维的形态。向背侧端脑的后区注射后，嗅球中有三种类型的神经元被填充：外部细胞层的二尖瓣细胞和有褶细胞，以及内部细胞层的神经元。尽管已知硬骨鱼中二尖瓣细胞和内部细胞层的神经元都从嗅球投射出去，但BDA的使用使得能够准确描述这些向外投射的神经元的形态。这是鲑鱼中有褶细胞从嗅球投射出去的首个证据。本研究结果表明，奇努克鲑鱼的次级嗅觉投射与其他硬骨鱼的投射一致，但有细微差异。数据还表明，嗅球传出纤维不仅起源于外部细胞层的二尖瓣细胞，还起源于外部细胞层的有褶细胞和内部细胞层的神经元。有人提出，内部细胞层向外投射的神经元在鲑鱼中构成前嗅核。
