[Regulatory effect of electroacupuncture at "Neiguan" (PC6) and "Zusanli" (ST36) with different intensities on autonomic nerves and cardiac function after myocardial ischemia].

LAD ligation successfully established a myocardial ischemia model with significant ECG, echocardiographic, and histological changes.

• After LAD ligation, ECG showed significant ST segment elevation (P<0.0001)
• EF and FS were significantly decreased (P<0.0001)
• Cardiac collagen volume fraction (CVF) was significantly increased (P<0.01)
• Model was evaluated using Lead II ECG, Masson staining, and Doppler echocardiography

Basal sympathetic nerve discharge frequency was significantly elevated in MI model rats compared to control rats.

• The basal discharge frequency of the left cervical sympathetic nerve (SN) in the model group was significantly higher than that in the control group (P<0.05)
• This finding was measured using in vivo neuroelectrophysiological recording at 7 days after MI induction
• 40 male SD rats were used, with 20 in each group

1.5 mA EA at PC6 was identified as the optimal intensity for improving cardiac function in MI rats.

• In the model group, 1.5 mA EA at PC6 led to increases in discharge frequency of both SN and VN (P<0.01 and P<0.05, respectively)
• HRV was increased in the model group with 1.5 mA EA at PC6 (P<0.001)
• SV, SW, and CO were all increased in the model group with 1.5 mA EA at PC6 (P<0.01, P<0.05, P<0.001)
• In the control group, 1.5 mA EA at PC6 resulted in increased HR (P<0.01) but did not improve cardiac output parameters as in the model group

3 mA EA at ST36 was identified as the optimal intensity for improving cardiac function in MI rats.

• In the model group, 3 mA EA at ST36 increased the discharge frequency of SN (P<0.05)
• SV, SW, and CO were all increased in the model group with 3 mA EA at ST36 (P<0.01)
• In the control group, 3 mA EA at ST36 induced an elevation of HR (P<0.05)
• 1.5 mA EA at ST36 in the model group only increased VN discharge frequency (P<0.05) without significantly improving cardiac output parameters

The cardiac function regulatory effects of EA at PC6 and ST36 were abolished following autonomic denervation.

• Autonomic denervation was performed in 10 MI model rats
• Before and after denervation, EA with the optimal intensity was delivered at left PC6 and ST36
• After autonomic denervation, the regulatory effects of EA at the above acupoints with optimal intensities on cardiac function were completely abolished
• This finding confirms that the autonomic nervous system is necessary for EA-induced cardiac regulation in MI rats

The two acupoints PC6 and ST36 have different optimal stimulation intensities and differential effects on sympathetic versus vagal nerve activity.

• PC6 at 1.5 mA activated both sympathetic nerve (SN) and vagal nerve (VN) discharge in MI rats
• ST36 at 1.5 mA only increased VN discharge frequency in MI rats (P<0.05)
• ST36 at 3 mA increased SN discharge and cardiac output parameters in MI rats
• EA was administered for 1 minute at each acupoint with intensities of 0.5, 1.5, and 3 mA tested