Objective To observe changes of the partial oxygen pressure in the deep tissues along the Large Intestine Meridian (LIM) during acupuncture stimulation

so as to reveal the characteristics of energy metabolism in the tissues along the LIM. Methods Thirty-one healthy volunteer subjects were enlisted in the present study. Partial oxygen pressure (POP) in the tissues (at a depth of about 1.5 cm) of acupoints Binao (LI 14)

Shouwuli (LI 13)

Shousanli (LI 10)

2 non-acupoints [the midpoints between Quchi (LI 11) and LI 14

and between Yangxi (LI 5) and LI 11) of the LIM

and 10 non-meridian points

1.5-2.0 cm lateral and medial to each of the tested points of the LIM was detected before

during and after electroacupuncture (EA) stimulation of Hegu (LI 4) by using a tissue oxygen tension needle-like sensor. Results In normal condition

the POP values in the deep tissues along the LIM were significantly higher than those of the non-meridian control points on its bilateral sides. During and after EA of Hegu (LI 4)

the POP levels decreased significantly in the deep tissues along the LIM in comparison with pre-EA (P<0.01)

and had no apparent changes in the non-meridian control points (P>0.05). Conclusion POP is significantly higher in the deep tissues along the LIM of healthy subjects under normal conditions

which can be downregulated by EA of Hegu (LI 4)

suggesting an increase of both the utilization rate of oxygen and energy metabolism after EA.