Novel anatomic structures in the brain and spinal cord of rabbit that may belong to the Bonghan system of potential acupuncture meridians.

Novel threadlike structures of 20 to 40 microm in diameter were observed running afloat in the cerebrospinal fluid of the brain ventricles and the spinal central canal of a rabbit. We developed an effective in situ staining technique using hematoxylin to visualize the threadlike structure. The presence of the rod-shaped nuclei in the threadlike structure was confirmed by various nucleus specific staining dyes such as 4',6'-diamidino-2-phenylindole, propidium iodide and yoyo-1. The threadlike structure was surrounded by a cellular membrane, whose presence was visualized by using 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate staining. The location, diameter, optical transparency and the presence of rod-shaped nuclei in and the surrounding membranes of the threadlike structure were consistent with a nerve Bonghan duct. The Bonghan duct was claimed to be the extension of the physical substance of acupuncture meridians and to be a distinct type of circulatory system present in mammals. Although Bonghan theory has not been reproduced for a long time, recently, some portions of the Bonghan duct network were confirmed in various organs in mammals including blood vessels, lymphatic vessels and enteric organs. The novel threadlike structure in the central nervous system, more specifically in brain ventricles, is one in a series of findings in an attempt to rediscover the Bonghan duct network.