β-Endorphinergic Neurons in Nucleus Arcuatus and Nucleus Tractus Solitarii Mediated Depressor-Bradycardia Effect of ‘tinggong’ 2Hz-Electroacupuncture

Abstract

The central neural mechanisms underlying the depressor -bradycardia effect of the “Tinggong” 2Hz-electroacupuncture (EA-DpB) were analyzed: 0.) 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 β -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 β-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 β-endorphinergic neurons in AR or NTS, the above results suggest that the EA-DpB is mediated by the β-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.