[Effect of electroacupuncture on electrical activities of pressor reflex related neurons in the nucleus of tractus solitarii (NTS) in rats].

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 presser 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 M(omega)). 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 microg/kg, 2 microg/mL).

Results: Of the 67 NTS neurons, 15 were activated by intravenous injection of PE (which were called as presser 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 presser 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 presser reflex induced increase of firing rates of NTS neurons, suggesting an interaction between signals from electroacupuncture stimulation of "Xin" and "Zusanli" (ST 36) and from cardiovascular activities in the NTS neurons.