Submitted on September 12, 2005
Accepted on February 17, 2006
Short-term electroacupuncture at Zusanli resets the arterial baroreflex neural arc toward lower sympathetic nerve activity
Daisaku Michikami1*, Atsunori Kamiya2, Toru Kawada2, Masashi Inagaki2, Toshiaki Shishido2, Kenta Yamamoto1, Hideto Ariumi1, Satoshi Iwase3, Junichi Sugenoya3, Kenji Sunagawa4, and Masaru Sugimachi2
1 Department of Cardiovascular Dynamics, Advanced Medical Engineering Center, National Cardiovascular Center Research Institute, Osaka, Japan; Pharmaceuticals and Medical Devices Agency, Tokyo, Japan
2 Department of Cardiovascular Dynamics, Advanced Medical Engineering Center, National Cardiovascular Center Research Institute, Osaka, Japan
3 UniversityDepartment of Physiology, School of Medicine Aichi Medical, Aichi, Japan
4 SciencesDepartment of Cardiovascular Medicine, Kyushu University Graduate School of Medical, Fukuoka, Japan
* To whom correspondence should be addressed. E-mail: dmichi{at}ri.ncvc.go.jp.
Although electroacupuncture reduces sympathetic nerve activity (SNA) and arterial pressure (AP), the effects of electroacupuncture on the arterial baroreflex remain to be systematically analyzed. We investigated the effects of electroacupuncture of Zusanli on the arterial baroreflex using an equilibrium diagram comprised of neural and peripheral arcs. In anesthetized, vagotomized, and aortic-denervated rabbits, we isolated carotid sinuses and changed intra-carotid sinus pressure (CSP) from 40 to 160 mmHg in increments of 20 mmHg per minute while recording cardiac SNA and AP. Electroacupuncture of Zusanli was applied with a pulse duration of 5 msec and a frequency of 1 Hz. An electric current 10 times the minimal threshold current required for visible muscle twitches was used, and was determined to be 4.8 ± 0.3 mA. Electroacupuncture for 8 min decreased SNA and AP (n=6). It shifted the neural arc (i.e. CSP-SNA relationship) to lower SNA, but did not affect the peripheral arc (i.e. SNA-AP relationship) (n=8). SNA and AP at the closed-loop operating point, determined by the intersection of the neural and peripheral arcs, decreased from 100 ± 4 to 80 ± 9 a.u. and from 108 ± 9 to 99 ± 8 mmHg (each, P<0.005), respectively. Peroneal denervation eliminated the shift of neural arc by electroacupuncture (n=6). Decreasing the pulse duration to less than 2.5 msec eliminated the effects of SNA and AP reduction. In conclusion, short-term electroacupuncture resets the neural arc to lower SNA, which moves the operating point toward lower AP and SNA under baroreflex closed-loop conditions.
