Objectives : To observe the changes in the expression of nNOS, iNOS, eNOS and NO by the needle insertion on river points, one of the five transport points of three yang meridians of the foot. Methods : Based on rats, needle was inserted on both left and right sides of ST41, BL60 and GB38 and retained for five minutes. After the retention, blood was drawn via cardiac puncture and tissues from each point around meridian vessels were extracted to observe the changes in the expression of nNOS, iNOS, eNOS and NO. Results : In terms of the effect on expression of nNOS within tissues, ST41 showed significant decrease based on the results of immunohistochemistry. In terms of the effect on expression of iNOS within tissues, none of the experimental groups showed any significant change compared to the Normal group. Regarding expression of eNOS within tissues, GB38 showed significant increase based on the results of immunohistochemistry. In terms of the effect on NO creation in tissues, none of the experimental groups showed any significant change compared to the Normal group. Conclusions : The effect of needle insertion on the river points of three yang meridians of the foot on the function of nNOS, iNOS, eNOS and NO could be observed, and based on this study, it is considered that the effect of needle stimulation on the changes of nervous system could be found out through additional research.