RESUMO
Objective: To investigate target organ response by recording mean arterial blood pressure (MAP) fluctuation corresponding to nerve-tract discharges from the nerve innervating acupoint of Zusanli (ST 36) in the hind limb evoked by MA in anesthetized rats. Methods: Male SD rats anesthetized with chloral hydrate were randomly divided into 3 groups which were treated with manual acupuncture (MA), injection of lidocaine followed by MA and injection of normal saline (NS) followed by MA, respectively. The right carotid artery was canulated for persistent measurement of the blood pressure and meanwhile nerve discharges from the nerve-tract were recorded for analysis with amplitude spike counts for every 5 s. Results: The results showed that there were significant nerve discharges recorded from the nerve-tract when applying MA at Zusanli (ST 36) and simultaneous decrease in the MAP, while there was no response when inserting a needle into the Zusanli (ST 36) without manipulation (P<0.05). Furthermore, the reduction of MAP during MA could be completely abolished after blockade of peripheral nerve discharges with an injection of lidocaine into the tissue around Zusanli (ST 36) but not with that of normal saline (NS). Conclusion: These results indicate that MA at Zusanli (ST 36) can elicit the peripheral nerve discharges from the nerve innervating the acupoint; such kind of nerve discharges may contain acupuncture signal regulating blood pressure via somato-cardiovascular reflex.