The primo vascular structures alongside nervous system: its discovery and functional limitation.

The primo vascular structures comprising primo nodes and vessels (originally called Bonghan corpuscles and ducts, resp.) have recently been suggested to be the anatomical correlate of acupuncture, a therapeutic technique used in oriental medicine. Although the primo vascular structures have been observed in many parts of animals, including the nervous system, using anatomical methodologies, its physiological functions are still unclear. This paper summarizes the reports on the primo vascular structures, particularly in the nervous system and its surroundings, as well as the electrophysiological properties of cells in the primo nodes. In addition, recent reports examining the potential roles of the primo vascular structures in acupuncture are discussed. This review raises some fundamental questions and, at the same time, highlights the potential physiological roles of the primo vascular structures in acupuncture.