Responses of nitric oxide release in acupoints/meridians to electroacupuncture in human skin in vivo using dermal microdialysis

The purpose of this study was to examine the responses of nitric oxide (NO) release in acupoints and non‐meridian areas to electroacupuncture (EA) in healthy volunteers. Microdialysis probe was sterilized and introduced into ST36 on leg (n=9) and into the PC4 on arm (n=14). Non‐point controls were conducted by probe placed into the skin located 5 mm away from PC4 or ST36. EA stimulation was applied to PC3 or ST40 on the same arm or leg with dialysis and was conducted using a 6 voltage pulse with a duration of 1.0 msec at 10 Hz for 20 min. The probes were perfused with sterile physiological fluid at a rate of 5μl per min. The dialysate was continually collected at a 20 min interval each. The responses to EA stimulation were measured at two intervals before, an interval during, and four intervals after EA. The concentrations of nitrite plus nitrate (NOx‐) in dialysate were assayed using a NO analyzer. The NOx‐ concentrations in the ST36 and PC4 dialysis were significantly higher at 20 min after EA than those collected before and during EA (p < 0.05). Dialysis at non‐acupoint did not alter NOx‐ concentrations following the same EA stimulation in both ST and PC groups. These results show that dialysate NOx‐ concentrations are consistently increased in ST 36 and PC4 by EA stimulation but not induced in non‐meridian areas. We conclude that EA‐evoked NO release is acupoint/meridian specific, and stimulus‐evoked peripheral NO release in acupoint/meridian may contribute to conductance of EA signals and therapeutic functions of acupuncture. Supported by NIH (AT00450, AT002478 , and HL04447) to S. Ma.