Electroacupuncture-induced pressor and chronotropic effects in anesthetized rats Jiuan-Miaw Liao a,e,1 , Hua Ting b,1 , Shin-Da Lee c , Chao-Hsun Yang d , Ying-Ming Liou e , Mei-Lin Peng f , Shih-Jei Tsai g , Chih-Feng Lin c , Tzer-Bin Lin a, * a Department of Physiology, College of Medicine Chung-Shan Medical University, No. 110, Chang-Kuo North Rd Section 1, Taichung, Taiwan 10018 b Division of Physical Medicine and Rehabilitation, Hospital and Chung Shan Medical University, Taichung, Taiwan c School of Physical Therapy, Colleges of Medicine, Hospital and Chung Shan Medical University, Taichung, Taiwan d Department of Cosmetic Science, Providence University, Taichung, Taiwan e Department of Life Science, National Chung-Hsing University, Taichung, Taiwan f Ophthalmology, Hospital and Chung Shan Medical University, Taichung, Taiwan g Neurology, Hospital and Chung Shan Medical University, Taichung, Taiwan Received 17 May 2005; received in revised form 13 October 2005; accepted 17 October 2005 Abstract The effects of electroacupuncture (Ea) on circulatory dynamics were investigated in anesthetized rats. The arterial blood pressure (BP) and the heart rate (HR) in response to Ea stimulations at the Tsusanli point (St-36) and the Hoku point (Li-4) were tested by a low frequency Ea (2 Hz; LFEa) and a high frequency Ea (20 Hz; HFEa) with stimulation intensities 20 times the motor threshold. Neither the HR nor the BP was affected when the Tsusanli point was stimulated. Whereas, Ea stimulations at the Hoku point elicit chronotropic and pressor effects. The patterns of pressor responses caused by the LFEa were different from that of an HFEa, i.e., the LFEa elicited a tonic effect, while an HFEa had a phasic one. The HFEa-induced pressor and chronotropic effects were attenuated, while the LFEa induced effects were completely blocked by an intravenous infusion of an alpha-adrenergic blocker (moxisylyte 0.2 mg/min/kg, i.v., for 20 min). A co-infusion with alpha-and beta-adrenergic blockers (propanolol 0.2 mg/min/kg, i.v., for 20 min) completely blocked the HFEa-induced pressor and chronotropic effects. We concluded that Ea stimulations, at the Hoku acupoint, with appropriate stimulation parameters can increase and maintain BP. Furthermore, the LFEa stimulation activates sympathetic vasomotor tone, whereas the HFEa stimulation causes an additional potentiation on the sympathetic drive to the heart. D 2005 Elsevier B.V. All rights reserved. Keywords: Heart rate; Blood pressure; Tsusanli; Hoku; Stimulation; Rat 1. Introduction In China, acupuncture has been used to treat various diseases for more than two thousand years. Researchers exploring the physiological mechanism underlying acu- puncture suggest that acupuncture might modulate nerve activities influencing visceral functions via somato – visceral reflexes (Tsuchiya et al., 1991; Sato et al., 1993; Kimura et al., 1995; Langevin et al., 2002). Electroacupuncture (Ea), where stimulation parameters can be clearly quantified, is not only used in clinical practice (Lewis et al., 1990; Lu and Lu, 1993), but is also widely used in animal (Sato et al., 1992, 1993) and human (Tsuchiya et al., 1991; Sugiyama et al., 1995; Averill et al., 2000) studies. Many studies exploring therapeutic effects elicited by Ea stimulations have concentrated on the cardiovascular system. Ea-induced pressor responses have been reported in normal subjects (Sugiyama et al., 1995; Tanaka et al., 2002) and anesthetized rats (Lin et al., 1998; Stener-Victorin 1566-0702/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.autneu.2005.10.005 * Corresponding author. Tel.: +886 4 2473 0022 11655; fax: +886 4 2473 9030. E-mail address: tblin@csmu.edu.tw (T.-B. Lin). 1 These two authors contributed equally to this study. Autonomic Neuroscience: Basic and Clinical 124 (2006) 18 – 25 www.elsevier.com/locate/autneu