Cummings D M, Emge D K, Small S L, Margolis F L
Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
J Comp Neurol. 2000 Jun 5;421(3):362-73.
The olfactory epithelium (OE) is unusual in its ability to regenerate and reinnervate its target, the olfactory bulb (OB), after deafferentation. To address the question of whether olfactory receptor neuron (ORN) axons preserve their topographic organization when they reestablish synaptic contact with the OB, the authors examined the pattern of ORN axon reinnervation into the bulb of adult H-OMP-lacZ-6 transgenic mice during and after recovery from chemical deafferentation. In the H-OMP-lacZ-6 mouse strain, lacZ expression is limited to a subset of ORNs that are distributed bilaterally in the OE and project primarily to a few glomeruli in the ventromedial region of the OB. The OE was lesioned by intranasal irrigation with Triton X-100, and the distribution of 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-gal)-stained cells was examined in the OE along with beta-galactosidase-immunoreactive (beta-gal-ir) axonal processes in the OB after short (1 week), intermediate (3 week), and long (6-7 weeks) recovery times. One week after the lesion, immunostaining for beta-gal and olfactory marker protein was virtually eliminated in the bulb. After 3 weeks of recovery, beta-gal-containing axons appeared to target many of the same locations innervated in bulbs of unlesioned mice. The region that received the highest density of axonal innervation in controls, however, contained only a few processes at that time. After 6-7 week recovery periods, the pattern of X-gal staining in the OE and beta-gal-ir axons in the OB closely resembled that of unlesioned mice. These results demonstrate that the topographic distribution of ORNs in the OE and the pattern of axon innervation in the OB can be reconstituted after chemical deafferentation.
嗅觉上皮（OE）具有独特的能力，即在去传入神经后能够再生并重新支配其靶器官——嗅球（OB）。为了解决嗅觉受体神经元（ORN）轴突在与OB重新建立突触联系时是否保留其拓扑组织的问题，作者研究了成年H - OMP - lacZ - 6转基因小鼠在化学去传入神经恢复期间及恢复后ORN轴突重新支配嗅球的模式。在H - OMP - lacZ - 6小鼠品系中，lacZ表达仅限于ORN的一个子集，这些ORN双侧分布在OE中，主要投射到OB腹内侧区域的少数几个肾小球。通过用Triton X - 100进行鼻内冲洗损伤OE，并在短（1周）、中（3周）和长（6 - 7周）恢复时间后，检查OE中5 - 溴 - 4 - 氯 - 3 - 吲哚基 - β - D - 半乳糖苷（X - gal）染色细胞的分布以及OB中β - 半乳糖苷酶免疫反应性（β - gal - ir）轴突过程。损伤后1周，嗅球中β - gal和嗅觉标记蛋白的免疫染色几乎消失。恢复3周后，含β - gal的轴突似乎靶向了未损伤小鼠嗅球中许多相同的支配位置。然而，在对照中接受轴突支配密度最高的区域，此时仅含有少数轴突。在6 - 7周的恢复期后，OE中X - gal染色模式和OB中β - gal - ir轴突与未损伤小鼠的模式非常相似。这些结果表明，化学去传入神经后，OE中ORN的拓扑分布和OB中轴突支配模式可以重新构建。
