Jonz Michael G, Nurse Colin A
Department of Biology, Life Sciences Building, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
J Comp Neurol. 2003 Jun 16;461(1):1-17. doi: 10.1002/cne.10680.
Peripheral chemoreceptors responsive to hypoxia have been well characterized in air-breathing vertebrates, but poorly in water-breathers. The present study examined the distribution of five populations of neuroepithelial cells (NECs), putative O(2) chemoreceptors, and innervation patterns in the zebrafish gill using whole-mounts and confocal immunofluorescence. Nerve bundles and fibers of the gill were labeled with zn-12 (a zebrafish-specific neuronal marker) and SV2 antisera and NECs were characterized by serotonin (5-HT) immunoreactivity (IR), SV2-IR and the purinoceptor P2X(3)-IR. A zn-12-IR nerve bundle extended the length of the gill filament and gave rise to a nerve plexus surrounding the efferent filament artery (eFA) and a rich network of fibers that innervated both serotonergic and nonserotonergic NECs of the filament and lamellar epithelium. Three populations of serotonergic, SV2-IR neurons intrinsic to the gill filaments are described, one of which provided innervation to NECs of the filament epithelium. Degeneration of nerve fibers in gill arches maintained in explant culture for 2 days revealed the extrinsic origin of nerve fibers of the plexus and lamellae and the innervation of filament NECs by both intrinsic and extrinsic fibers. Intrinsic innervation surrounding the eFA survived in explant cultures, suggesting a mechanism of local vascular control within the gill. In addition, NECs survived in explants after degeneration of extrinsic nerve fibers. Thus, NECs of the zebrafish gill are organized in a manner reminiscent of O(2) chemoreceptors of mammalian vertebrates, suggesting a role in respiratory regulation.
对缺氧有反应的外周化学感受器在空气呼吸的脊椎动物中已得到充分研究，但在水呼吸动物中了解甚少。本研究使用整装标本和共聚焦免疫荧光技术，研究了斑马鱼鳃中五群神经上皮细胞（NECs）（推测为O₂化学感受器）的分布及神经支配模式。鳃的神经束和纤维用zn-12（一种斑马鱼特异性神经元标记物）和SV2抗血清标记，NECs通过5-羟色胺（5-HT）免疫反应性（IR）、SV2-IR和嘌呤受体P2X₃-IR进行鉴定。一条zn-12-IR神经束沿着鳃丝全长延伸，形成围绕传出鳃丝动脉（eFA）的神经丛以及丰富的纤维网络，这些纤维支配鳃丝和片状上皮中的5-羟色胺能和非5-羟色胺能NECs。描述了鳃丝中固有的三群5-羟色胺能、SV2-IR神经元，其中一群为鳃丝上皮的NECs提供神经支配。在体外培养2天的鳃弓中神经纤维的退化揭示了神经丛和鳃小片神经纤维的外源性起源以及固有和外源性纤维对鳃丝NECs的神经支配。围绕eFA的固有神经支配在体外培养物中存活，提示鳃内局部血管控制机制。此外，在外源性神经纤维退化后，NECs在体外培养物中存活。因此，斑马鱼鳃中的NECs以类似于哺乳动物脊椎动物O₂化学感受器的方式组织，提示其在呼吸调节中的作用。
