D70eee

A total of 6 mongrel dogs were studied. A radiotransmitter (D70EEE, Data Sciences International, St. Paul, MN) was implanted to record SGNA, vagal nerve activity (VNA) and ScNA. A Cyberonics of Model 304 bipolar vagal stimulating lead was implanted around subcutaneous nerves at Xinshu acupoint and connected to a Cyberonics Demipulse neurostimulator (Cyberonics Inc, Houston, TX). After baseline recording, the neurostimulator was turned on and programmed to 14-s ON and 1.1-min OFF (10 Hz, 500 µs pulse duration) in all dogs. The output current (mA) was progressively increased to 3.5 mA over 2 weeks (Figure 1A). We found that the dogs tolerated 3.5 mA ScNS without showing signs of discomfort or reduced appetite.

Figure 1 shows the research
protocol. Thirteen mongrel dogs (23-30 kg) underwent isoflurane inhalation
general anesthesia and sterile left lateral thoracotomy through the forth
intercostal space. A radiotransmitter (D70EEE, Data Sciences International, St.
Paul, MN) was implanted to record SGNA and vagal nerve activity (VNA). A
modified Medtronic Secura pacemaker (Medtronic Inc, Minneapolis, MN) was
implanted during the same surgery for intermittent rapid atrial pacing through a
pacing lead sutured onto the left atrial (LA) appendage. The skin incision was
then extended to the back to reach left Xinshu acupoint (BL15, approximately 5
cm lateral to the spine at T5 level) as in a previous study.^{12 (link)} The subcutaneous space was explored to
locate visible subcutaneous nerves and blood vessels in that area. A Cyberonics
Model 304 bipolar vagal stimulating lead was implanted around these small
subcutaneous nerves and connected to a subcutaneously positioned Cyberonics
Demipulse neurostimulator (Cyberonics Inc, Houston, TX) (Online supplement Figure
1). A third pair of the bipolar recording electrodes from the D70EEE
radiotransmitter was placed in the subcutaneous tissue to record from the nerves
being stimulated, with the two electrodes bracketing the point of stimulation.
The latter bipolar leads have an interelectrode distance of > 4 cm. The
chest was then closed.

For pacemaker and radiotransmitter implantation, a right thoracotomy was performed through the fourth intercostal space. Anesthesia was induced with ketamine (5–10 mg/kg) and midazolam (0.1–0.2 mg/kg IV), and after intubation and mechanical ventilation, anesthesia was maintained with 2.0% isoflurane. An epicardial pacing lead was implanted onto the right atrial appendage and connected to a subcutaneously positioned Medtronic Secura implantable pacemaker (Medtronic Inc, Minneapolis, MN) that was modified for high rate (600bpm) atrial pacing. A radiotransmitter (D70EEE, Data Sciences International, St. Paul, MN) with 3 bipolar recording electrodes was implanted to record nerve activity and an electrocardiogram (ECG).(16 (link),17 (link)) To record IVC-IAGPNA, electrodes were sutured onto the IVC-IAGP beneath its fascia. To record right vagal nerve activity (RVNA), electrodes were sutured onto the superior cardiac branch of the right vagal nerve. To record left vagal nerve activity (LVNA), electrodes were placed on the left cervical vagal nerve. For vagal nerve stimulation, a bipolar stimulating lead was implanted around the left cervical vagal nerve and connected to a subcutaneously positioned Cyberonics Demi-pulse neurostimulator (Cyberonics Inc, Houston, TX).