Objective According to the theory of traditional Chinese medicine about"close association between the lung and the large intestine"

the present study was designed to investigate the functional relationship between the Lung and Large Intestine Meridians and the colorectum by using electrophysiological methods.Methods A total of 40SD rats were used in the present study.Under anesthesia

the cardiopulmonary branch of the left sympathetic nerve(CPSN)was separated for recording the electrical activities with a pair of platinum wire electrodes.Intra-colorectal pressure was recorded using a water-balloon inserted into the anus and connected to a pressure-transducer for observing rectocolonic pressure changes(mobility).Electroacupuncture(EA)stimulation was applied to bilateral"Taiyuan"(LU 9)-"Jingqu"(LU 8)of the Lung Meridian

"Yangxi"(LI 5)-"Pianli"(LI 6)of the Large Intestine Meridian

and"Shangjuxu"(ST 37)-"Zusanli"(ST 36)of the Stomach Meridian

respectively.Colorectal distension(CRD

visceral pain stimulation

60mmHg and 80mmHg)was performed using an air-balloon for observing its influence on EA stimulation of LU 9-LU 8induced changes of electrical activities of CPSN.Results Under anesthesia conditions

no spontaneous electrical activities of the CPSN were found in rats.After EA stimulation(3times of the threshold intensity)of the bilateral"Taiyuan"(LU 9)-"Jingqu"(LU 8)of the Lung Meridian

and"Yangxi"(LI 5)-"Pianli"(LI 6)of the Large Intestine Meridian

the evoked discharge numbers of the cardiopulmonary sympathetic nerve were(11.26±2.34)and(10.73± 2.62)spikes

respectively

without significant differences between the two groups(P>0.05).Compared with pre-stimulation

the colorectal motility(amplitudes of the intra-colorectal pressure waves)was obviously increased following EA stimulation of LU 9-LU 8of the Lung Meridian

LI 5-LI 6of the Large Intestine Meridian and"Shangjuxu"(ST 37)-"Zusanli"(ST 36)

Lower-Ho (Sea)acupoints of the Large Intestine Meridian(P<0.05).After CRD stimulation at 60mmHg and 80mmHg

the LU 9-LU 8-stimulation evoked discharge rates of CPSN were reduced by 43.46% and 67.42%

respectively.Conclusion EA stimulation of LU 9-LU 8of the Lung Meridian and LI 5-LI 6of the Large Intestine Meridian can activate discharges of CPSN

and increase the colorectal motility in the rat.CRD stimulation inhibits the activated effect of EA on electrical activities of CPSN.These results show a functional communication or cross-talk between the lung and the colorectum.