Understanding Qi Running in the Meridians as Interstitial Fluid Flowing via Interstitial Space of Low Hydraulic Resistance

Qi, blood and the meridians are fundamental concepts in Chinese medicine（CM）, which are components of the human body and maintain physiological function. Pathological changes of qi, blood and meridians may lead to discomfort and disease. Treatment with acupuncture or herbal medicine aims to regulate qi and blood so as to recover normal function of the meridians. This paper explores the nature of qi as well as compares and correlates them with the structures of the human body. We propose a conceptualization of qi as being similar to the interstitial fluid, and the meridians as being similar to interstitial space of low hydraulic resistance in the body. Hence, qi running in the meridians can be understood as interstitial fluid flowing via interstitial space of low hydraulic resistance.

A discovery of low hydraulic resistance channels along meridians in rats

Background:Continuous and porous low hydraulic resistance channels(LHRCs)are important structures of meridians in traditional Chinese medicine(TCM).In this study,based on the previous research on LHRCs along meridian paths(LHRCMs)in mini-pig,we aimed to detect the low hydraulic resistance point(LHRP)and display the LHRCMs in rats.Methods:A technique for measuring interstitial hydraulic resistance(Rh)in rats was established to detect and measure the Rh along the conception vessel(CV)in TCM,and Alcian Blue(AB)solution was injected into the LHRP along the CV.The interstitial fluid pressure(IFP)of the LHRP was measured before and after AB injection.Then,the distribution characteristics of the AB solution were investigated to explore the relationship between AB tracks and meridian paths in TCM.Results:The positions of the LHRPs coincided with the low impedance points(LIPs)of the rat skin along the CV.The Rh value along the CV(10.37,1.26,×10^(6)dyne s cm^(-5))was significantly lower than that in the non-meridian area(19.13±1.37,×10^(6)dyne s cm^(-5),P<0.01).After AB injection,the IFP of the LHRP was 2.52 mmHg,which was higher than that before AB injection.The AB tracks(ABT)along the CV,spleen meridian,and kidney meridian appeared in one or two directions,with single or multiple paths and uneven thickness and length.The appearance rate was 73.33%.Conclusions:LHRCMs existed not only in minipigs but also in rats.The LHRCMs could be observed after AB injection into the LHRP in the subcutaneous connective tissues of rats.

Understanding Propagated Sensation along Meridians by Volume Transmission in Peripheral Tissue

Propagated sensation along meridians （PSM） is a phenomenon that a sensation moves along meridians during stimulation of an acupoint. PSM has an appearance rate of 1.3% among people and have characteristics of low speed, going toward afflicted sites and being blocked by physical pressure which is difficult to be explained by known neural and blood transmission. Volume transmission （VT） is a widespread mode of intercellular communication in the central nervous system that occurs in the extracellular fluid and in the cerebrospinal fluid. VT signals moves from source to target cells via energy gradients leading to diffusion and convection （flow） which is slow, long distance and much less space filling. VT channel diffuse forming a plexus in the extracellular space with two parameters of volume fraction and tortuosity. Some experiments showed an information transmission between adjacent and distant acupoints along meridians cross spinal segments. This process is a cross-excitation between peripheral nerve terminals which is related to nonsynaptic transmission. Some neurotransmitters or neuropeptides such as glutamate, adenosine triphosphate （ATP） and neuropeptide such as substance P, neurokinin A and calcitonin gene-related peptide relate with the cross-excitation which can be regards as VT signals. Comparing the characteristics of PSM and VT, many similar aspects can be found leading to an assumption that PSM is a process of VT in peripheral tissue along meridians. The reason why VT signals transmit along meridians is that the meridian is rich in interstitial fluid under the condition of low hydraulic resistance which has been proven experimentally. According to Darcy＇s law which descript the flow of interstitial fluid and conservation equation, interstitial fluid will move toward meridians and flow along meridians that restrict the VT signals within the channel and accelerate the flow according to Fick＇s diffusion law. During the process, a degranulation of histamine from mast cells happens on the route which can expand capillary and increase the blood perfusion and interstitial fluid which had already been observed. The mechanism of PSM is featured by alternative axon reflex （wired transmission, WT） and VT in peripheral tissue along meridians, sending simultaneously a continuous sensate signal to control nerve system which can be felt like a PSM.