Abstract:Objective: To check whether the mediodorsal thalamic nucleus(MD) participate in the message transmission of visceral pain(VP), and if electro-acupuncture(EA) inhibits it or not. Methods: By microelectrode and extracellular recording,the effect of the evoked discharges in MD to induce VP,and the effect of EA on evoked discharges in MD induced by VP were observed in rats. The acupoint selected was ZUSANLI,and the control point is the ipsilateral lateral ankle. Results: 1. VP could evoke unit discharges in MD of rats. 2. EA markedly inhibited the unit pain discharges induced by VP. Obvious difference was observed between acupoint and non-acupoint. Conclusion: MD receives the afferent messages of visceral pain,and may play a role in analgesia of acupuncture.