Submitted on February 20, 2008
Revised on June 20, 2008
Accepted on June 24, 2008
The Effect of Electrical Stimulation of the Lower Esophageal Sphincter (LES) on LES Pressure in a canine model
Claudia P Sanmiguel1, Masanobu Hagiike1, Martin P Mintchev2, Ryan Dela Cruz, Edward H Phillips, Scott A Cunneen, Jeffrey L Conklin, and Edy E Soffer3*
1 Cedars Sinai Medical Center
2 University of Calgary
3 Center for Digestive Diseases
* To whom correspondence should be addressed. E-mail: edy.soffer{at}cshs.org.
Gastric electrical stimulation (GES) modulates lower esophageal sphincter pressure (LESP). High-frequency neural stimulation (NES) can induce gut smooth muscle contractions. To determine if lower esophageal sphincter (LES) electrical stimulation (ES) can affect LESP, bipolar electrodes were implanted in the LES of four dogs. Esophageal manometry during sham or ES, was performed randomly on separate days. Four stimuli were used: 1) Low frequency, 350msec pulses at 6 cycles/min; 2) High-frequency-1: 1msec pulses at 50Hz; 3) High-frequency-2: 1msec pulses at 20Hz; and 4) NES: 20msec bipolar pulses at 50Hz. Recordings were obtained postprandially. Tests consisted of three 20-minute periods: baseline, stimulation/sham and post-stimulation. The effect of NES was tested under anesthesia and following IV administration of L-NAME and atropine. Area under the curve (AUC) and LESP were compared among the 3 periods, using ANOVA and t-test, p<0.05. Data are shown as mean±SD. We found that low-frequency stimulation caused a sustained increase in LESP: 32.1±12.9 (pre-stimulation) vs. 43.2±18.0 (stimulation) vs. 50.1±23.8 (post-stimulation), p<0.05. AUC significantly increased during and after stimulation. There were no significant changes with other types of ES. With NES, LESP initially rose and then decreased below baseline (LES relaxation). During NES, L-NAME increased both resting LESP and the initial rise in LESP, and markedly diminished the relaxation. Atropine lowered resting LESP and abolished the initial rise in LESP. In conclusion, low frequency ES of the LES increases LESP in conscious dogs. NES has dual effect on LESP: an initial stimulation, cholinergically mediated, followed by relaxation mediated by nitric oxide.
