Electroacupuncture at Hoku elicits dual effect on autonomic nervous system in anesthetized rats

To address the effect of electroacupuncture (Ea) on the autonomic nerve activity, responses of arteriole blood pressure (BP), intragastric pressure (IGP) and parasympathetic vagal nerve activity (VNA) to Ea were investigated in alpha-chloralose anesthetized rats. The acupoint: Hoku (Li-4) was tested with two different stimulation frequencies (2 and 20 Hz). Decrease in VNA and basal IGP associated with elevation of BP were elicited during Ea at Hoku with stimulation intensity of 20 times of motor threshold. The pattern of response induced by the low frequency Ea (LFEa) was different from that by the high frequency Ea (HFEa), i.e. a tonic effect was elicited by the LFEa, while a phasic one was induced by the HFEa. All the results in this study implicated that: (1) Ea at Hoku may activate the sympathetic and simultaneously inhibit the gastric parasympathetic nerve; (2) Ea at Hoku with different stimulation frequencies may elicit distinct mechanism to induce therapeutic effect; (3) Ea at Hoku may ameliorate the hyperactive stomach in clinical therapy.