[Entity of acupoint: kinetic changes of acupoints in histocytochemistry]

The present study aims to investigate the kinetic histocytochemical changes of acupoints in different condition. The expression of tryptase (+) mast cells, histamine (HA) , serotonin (5-HT) and nociceptive neuropeptides including calcitonin gene-related peptide (CGRP) and substance P (SP) were observed by immunohistochemistry combined with confocal technology. Mast cells were labeled with anti-mast cell tryptase antibody and simultaneously with HA or 5-HT primary antibodies to observe their co-expression. The results showed that: (1) SP and CGRP were expressed more highly on the cutaneous nerve fibers of "Hegu" (LI 4) after acupuncture stimulation than that of the control. Mast cells aggregated in close proximity to the blood vessels in intra-epidermis and dermis, and some of them with degranulation in the lower dermis and subcutaneous tissue of "Hegu" (LI 4). Both mast cells and their granules appeared with HA (+) and 5-HT (+) expression at stimulated LI 4 sites, while a few intact mast cells with a little expression of 5-HT and HA were distributed in areas of non-stimulated Ll 4. (2) The acupoints in different locations such as Baihui (GV 20), Weishu (BL 21), Zhongwan (CV 12) and LI 4 had the same constituent but the contents were different. (3) The histocytochemical responses of acupoints sensitized by the Gastric mucosa injury (GMI) were also investigated. GMI resulted in neurogenic plasma extravasation by Evans Blue (EB) in the skin of the acupoints over the back and abdomen, which mostly occurred in the T9-T11 dermatomere. The EB extravasation dots just like acupoints sensitization appeared after GMI and disappeared gradually during the natural self-recovery of the gastric mucosa. More SP and CGRP positive nerve fibers were distributed in EB dots than in regions beside EB dots and in the control, mostly distributed in the nerve fibers around both the vessels and root of hair follicle. Mast cells also aggregated and degranulated to release algogenic substances of 5-HT and HA around the vessels in areas of the EB dots. Collectively the acupoints displayed the same histocytochemical responses due to either acupuncture stimulation or GMI. This may potentially be the histocytochemical basis in the local acupoints and acupoints displayed kinetic changes in different condition.