Objective To observe the effect of electroacupuncture(EA)of auricular point "Xin"(Heart)

"Neiguan"(PC 6) and "Zusanli"(ST 36) on electrical activities of the pressor reflex-related neurons in the nucleus of the solitary tract(NTS)in rats.Methods A total of 47 SD rats were used in the present study.Extracellular electrical activities of neurons in the NTS(AP:1.0 mm

Left and right:0-1.0 mm

depth:0.3-0.8 mm)were recorded by using glass microelectrodes(10-15 MΩ).Carotid arterial pressure changes were monitored and recorded by using a pressure transducer.EA(2 mA

10 Hz

duration: 500 ms)was randomly applied to the left auricular point "Xin"

"Neiguan"(PC 6)and "Zusanli"(ST 36) for 30 s

respectively.Elevation of arterial pressure was induced by intravenous injection of Phenylephrine(PE

6-12 μg/kg

2 μg/mL).Results Of the 67 NTS neurons

15 were activated by intravenous injection of PE(which were called as pressor reflex-related neurons).Following EA of the auricular point "Xin" and ST 36

the mean arterial pressure(MAP) levels in normal rats and PE-induced MAP increase rats were lowered significantly(P<0.001

P<0.05).Concomitantly

the firing rates of pressor reflex-related NTS neurons were increased considerably by EA stimulation of auricular point "Xin" and ST 36

but not by EA of PC 6.EA of PC 6 had no apparent influence on MAP in normal rats and in PE-induced MAP increase rats(P>0.05).Conclusion Electroacupuncture stimulation of auricular point "Xin" and "Zusanli"(ST 36) can lower MAP in normal rats and PE-induced MAP elevation rats

and enhance pressor reflex induced increase of firing rates of NTS neurons

suggesting an interaction between signals from electroacupuncture sti-mulation of "Xin" and "Zusanli"(ST 36) and from cardiovascular activities in the NTS neurons.