Tolbert L P, Sirianni P A
Arizona Research Laboratories Division of Neurobiology, University of Arizona, Tucson 85721.
J Comp Neurol. 1990 Aug 1;298(1):69-82. doi: 10.1002/cne.902980106.
The role of antennal sensory axons in the induction and stabilization of olfactory glomeruli has been explored in the moth Manduca sexta. First, we asked the question: how many axons are necessary to induce glomerulus formation within the first-order olfactory neuropil of the brain? Axons from as few as 10 of the normal 70-80 repeating antennal segments were sufficient to induce glomeruli. However, there was a dose dependence in the number of glomeruli that developed in partially innervated lobes. When only 11 segments of the antenna were allowed to provide innervation to the lobe, only 37 of the normal 59 +/- 2 glomeruli developed; over 20 segments were necessary to induce the normal number of glomeruli. In a second set of experiments, we asked: for how long must antennal axons be present to stabilize newly formed glomeruli? We found that antennal axons must be intact for at least 2 to 4 stages (roughly equivalent to 2 to 4 days) for glomeruli to be stable even if the axons are subsequently severed. This finding, taken in the light of other recent findings in our laboratory, suggests that the formation of synapses may be a crucial element in the stabilization of glomerular structure. All together, the results of the present study indicate that induction and stabilization of glomeruli are separable events with different underlying cellular bases.
触角感觉轴突在蛾类烟草天蛾嗅觉小球的诱导和稳定过程中的作用已得到研究。首先，我们提出一个问题：在大脑的一级嗅觉神经纤维网内诱导小球形成需要多少轴突？来自正常70 - 80个重复触角节段中少至10个节段的轴突就足以诱导小球形成。然而，在部分神经支配的叶中发育的小球数量存在剂量依赖性。当仅允许11个触角节段为叶提供神经支配时，正常的59±2个小球中仅发育出37个；需要超过20个节段才能诱导出正常数量的小球。在第二组实验中，我们问道：触角轴突必须存在多长时间才能稳定新形成的小球？我们发现，即使轴突随后被切断，触角轴突也必须完整至少2至4个阶段（大致相当于2至4天），小球才能稳定。结合我们实验室最近的其他发现，这一发现表明突触的形成可能是小球结构稳定的关键因素。总之，本研究结果表明，小球的诱导和稳定是具有不同潜在细胞基础的可分离事件。
