Beta-endorphinergic neurons in nucleus arcuatus and nucleus tractus solitarii mediated depressor-bradycardia effect of "Tinggong" 2Hz-electroacupuncture.

The central neural mechanisms underlying the depressor-bradycardia effect of the "Tinggong" 2Hz-electroacupuncture (EA-DpB) were analyzed: (1) Brain transection caudal to nucleus arcuatus (AR) or procaine preinjection into bilateral AR could block the EA-DpB; (2) preinjection of naloxone into bilateral nucleus paraventricularis could even reverse the EA-DpB, but beta-endorphin antiserum had no significant effect on the EA-DpB; (3) after procaine injection into the nucleus commissuraris (the caudal part of NTS), the EA-DpB was also blocked; (4) preinjection of naloxone or beta-endorphin antiserum into bilateral rostral ventrolateral medulla (RVL) attenuated or reversed the EA-DpB response, taken together with our previous findings that the RVL mediates the depressor response to the excitation of the beta-endorphinergic neurons in AR or NTS, the above results suggest that the EA-DpB is mediated by the beta-endorphinergic projections from the AR and NTS to RVL. Finally the mechanism underlying the reverse of the EA-DpB by naloxone injection into nucleus paraventricularis was discussed.