Pressor effect on blood pressure and renal nerve activity elicited by electroacupuncture in intact and acute hemorrhage rats

The neural mechanism underlying the effect of electroacupuncture (Ea) on arterial blood pressure (BP) and renal nerve activity (RNA) in the intact state and during acute hemorrhage was investigated in anesthetized rats. Two acupoints, Hoku (Li-4, at the junction of the first and the second metacarpal bone) and Tsusanli (St-36, at the lateral upper tibia bone), were tested using Ea of two different frequencies (2 and 20 Hz). In the intact state, Ea at Hoku elicited an elevation of BP in parallel with RNA, while Ea found no response with identical parameters at Tsusanli. The pattern of the pressor response caused by a low frequency Ea (2 Hz) at Hoku was different than a high frequency one (20 Hz), i.e. a tonic effect was elicited with 2 Hz, while a phasic one was induced with 20 Hz. In mild hemorrhage conditions (10% of BP decrease), similar pressor effects, as in intact rats, were also elicited by Ea. However, in severe hemorrhage conditions (20 and 30% BP decrease), Ea induced a pressor effect on RNA and an attenuated effect on BP. BP and RNA showed a significant correlation in intact and mild hemorrhage conditions, but not in severe hemorrhage conditions. All the results suggested that Ea at Hoku with appropriate stimulation parameters can increase and maintain BP in normal and hemorrhage conditions, and such a therapeutic technique has potential in clinical practice.