Effect of electroacupuncture on blood pressure and adrenal nerve activity in anesthetized rats

The neural mechanism underlying the effect of electroacupuncture (Ea) on ar terial blood pressure (BP) and adrenal nerve activity (ANA) was investigate d in anesthetized rats. Tsusanli (St-36) and Hoku (Li-4) were tested with c ombinations of two different frequencies (3 and 30 Hz) with various stimula tion intensities of Ea. At Tsusanli, no effect was found, while at Hoku, an elevation of BP in parallel with ANA was elicited during Ea when the inten sity was 5 x Tor higher. The pattern of the presser response caused by the low frequency Ea (LFEa, 3 Hz) was a tonic one, while a phasic one was induc ed by the high frequency Ea (HFEa, 30 Hz). When both Hoku were simultaneous ly stimulated with the same frequency, the latency to reach the maximal eff ect was shortened. However, when two different frequencies were used instea d, a response characterized by a combination of both phasic and tonic effec t was obtained. In bilateral Ea with idential frequency but different onset time, the presser effect elicited by the latter Ea showed no further incre ase during the stimulation period, however, when different frequencies were employed, each Ea elicited its own effect independently. The presser effec t elicited by La was abolished by regitine but not affected by adrenalectom y. It is concluded that a LFEa and a HFEa at Hoku with appropriate stimulat ion parameters can increase BP which is mainly due to potentiation of the s ympathetic vasoconstrictor tone but via different central mechanisms. (C) 2 000 Elsevier Science Ireland Ltd. All rights reserved.