Objective To observe the dynamic distribution of the extravasated Evans Blue(EB)dye points at the skin after acute colorectal mucosal injury(AIMI)so as to reveal characteristics of acupoint sensitization.Methods Forty adult male SD rats were randomly divided into control(n=10)

AIMI(n=20)and AIMI-recovery(n=10)groups.According to the reaction state(EB-dye extravasation)

each group was further divided into resting state(control)

sensitized state(appearance of extravasated EB points)

recovery state(disappearance of the extravasated EB points)

non-sensitization(NS

no extravasated EB points)state and NS recovery state.The AIMI model was induced by perfusion of 2.5% mustard oil into the colorectum via a thin tube.Evans blue dye was injected into the caudal vein 4hafter AIMI modeling.The distribution of plasma extravasated EB dye points at the skin of the lower limbs was observed.The C-fiber discharge of the separated ipsilateral sciatic nerve was induced by electrical stimulation of the EB-extravasated acupoints and non-acupoint at the threshold and double-fold threshold using an electric stimulator and recorded using a bioelectric amplifier-computer system.Results In AIMI rats

the extravasated EB-dye points were found to overlap the"Xiqian"and"Zusanli"(ST 36)-"Shangjuxu"(ST 37)regions.Moreover

the thresholds of C-fiber discharges induced by electrical stimulation of"Xiqian"and"Zusanli"(ST 36)-"Shangjuxu"(ST 37)regions were significantly lower than those of the regions without extravasated EB dye acupoint and non-acupoint(P<0.01

P<0.05).The numbers of C-fiber discharges evoked by 2-fold threshold electro-stimulation at the "Xiqian"and "Zusanli"(ST 36)-"Shangjuxu"(ST 37)regions were obviously more than those of stimulation of non-acupoint which were experiencing sensitized state(P<0.01

P<0.05).Conclusion In rats with acute colorectal mucosal injury

electrical stimulation of the acupoints where the extravasated EB-dye points appear may produce an obvious increase of C-fiber discharges under lower electro-stimulation threshold

suggesting a larger action of the sensitized acupoint.