Effects of Different Connection Modes of Electroacupuncture on Electrocardiogram and Nerve Discharge in Rats

We aim to compare the effects of different electroacupuncture connection modes on ECG and neuro discharge in rats, and found the most suitable way of electroacupuncture connection. During the use of EA, the interference of the frequency of EA on the recording of the data, such as ECG and neuro discharge, is a major challenge at present. We found that the manner in which the positive and active electrodes of EA were connected in both upper limb affected heart rate and neuro discharge in rats.

[Instructor] To begin, arrange all the required sterile instruments for the procedure. For ECG connection, restrain the anesthetized rat in the supine position on a thermostatic plate set to 37 degrees Celsius. Moisten the rat's eyes with erythromycin ointment. Insert half-inch acupuncture needles parallel to the skin of the right forelimb wrist, right hind limb, and left hind limb of the rat. To connect the needle handles to the recording electrodes, attach the white positive electrode to the right forelimb, the red negative electrode to the left hind limb, and the black reference electrode to the right hind limb of the rat. Use a physiological signal recorder to record the standard limb lead surface ECG of the rat in real time. For separation of the vagus nerve, make a two to four centimeter incision along the midline of the neck between the larynx and the sternum. Sever the right vagus nerve trunk after locating the right carotid sheath, which contains the carotid artery, vagus nerve, and sympathetic chain. Connect the nerve trunk with a pair of copper hook electrodes and clamp the reference electrode to the incision to eliminate interference. Use saline to maintain vagus nerve activity throughout the experiment. Cover the surface wound with mineral oil to maintain insulation between the electrode and the muscle. Use a physiological signal recorder to record the vagal nerve discharge of the rat in real time. For electroacupuncture, connect the two needle handles separately to the needle clips of the electroacupuncture, or EA, instrument. Set the EA stimulation to a bi-directional square wave with appropriate parameters. Observe the changes in ECG and nerve discharge of the rat under different connection modes of EA in real time. Collect data for 30 seconds without any stimulation, 30 seconds before EA and 30 seconds after EA using the physiological signal recorder. Control rats had heart rates ranging from 258 to 473 beats per minute, with significant baseline differences. Groups A and B showed no significant changes in heart rate or ECG waveform after EA stimulation. Group C and D had increased heart rates post-EA, which quickly returned to baseline without affecting waveforms. Group E showed pronounced effects with heart rate increases after 20 minutes of EA. Abnormal p-waves and elevated ST segments persisted throughout the observation period. Vagal nerve discharges in control and group A rats were unaffected. Group B showed minimal changes, with stable discharge amplitude despite increased EA currents. Group C rats exhibited stable discharge values despite significant electric fields. Group D showed a slight frequency reduction with no significant data impact. Group E had reduced bundle discharges and increased peak discharge values.