Effect of prolonged gastric distension on motor function of LES and of proximal stomach

Abstract

Allocca, M., M. Mangano, and R. Penagini. Effect of prolonged gastric distension on motor function of LES and of proximal stomach. Am J Physiol Gastrointest Liver Physiol 283: G677-G680, 2002. First published April 10, 2002 10.1152/ajpgi.00526.2001.-Gastric distension is a potent stimulus of transient lower esophageal sphincter (LES) relaxation. To investigate the time effect of prolonged gastric distension on the rate of transient LES relaxations, LES pressure, and the motor and sensory functions of the proximal stomach, we performed a continuous isobaric distension of the proximal stomach at the 75% threshold pressure for discomfort for 2 h in seven healthy subjects. A multilumen assembly incorporating a sleeve and an electronic barostat was used. The rate of transient LES relaxations (n/30 min) was constant during the first hour [4.1 Ϯ 1.2 (0-30 min) and 5.4 Ϯ 1.1 (30-60 min)] but markedly decreased (P Ͻ 0.05) in the second hour [2.1 Ϯ 0.5 (60-90 min) and 2.3 Ϯ 0.9 (90-120 min)], whereas LES pressure, baseline volume and volume waves within the gastric bag, hunger, and fullness did not change throughout the experiment. It is concluded that the rate of transient LES relaxations decreases with time during prolonged gastric distension, thus suggesting that this type of stimulus should not be used in sequential experimental conditions. gastric tone; lower esophageal sphincter pressure; barostat TRANSIENT LOWER ESOPHAGEAL SPHINCTER (LES) relaxation is the mechanism that allows venting of gas during belching, and it is now established to represent an important motor event underlying gastroesophageal reflux (GER) in patients with GER disease (6, 16). There is ongoing interest in developing drugs that can decrease GER by interfering with transient LES relaxations (3,9,14,15,19). In addition to exploring possible new approaches to the treatment of GER disease, this research is valuable in gathering information concerning the neural pathways involved in the control of transient LES relaxations. To perform studies of an acceptable duration, the rate of transient LES relaxations needs to be stimulated. This has so far been done by means of various experimental models that have used proximal gastric distension as a stimulus (7, 10). The most physiological model is the ingestion of a meal, but because the rate of transient LES relaxations is not constant over the postprandial period (11, 18), presumably because of gastric emptying, it is difficult to assess more than one experimental condition per day. Furthermore, this model, as well as others using gas (24), liquid infusion in the fundus (12, 19), or balloon inflation without the use of a barostat (10), does not allow simultaneous monitoring of the effects of the study drug on the rate of transient LES relaxations and proximal gastric motor function. Understanding the relationship between these two variables is vital to increase our knowledge of the control of transient LES relaxations and for future drug development (23).Distension of the proximal stomach by means of a...

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“…Motor function of the proximal stomach was measured with an electronic barostat (Synectics Visceral Stimulator, Sweden), as previously described (2). The latter was able to maintain a constant volume in a polyethylene bag that had a capacity of approximately 1,400 ml via a tube of 2.5 mm internal diameter (ID) and 650-mm length.…”

“…Although it is established that distension of the proximal stomach induces the perception of fullness (1,2), the underlying mechanisms are poorly defined. Two types of mechanoreceptors are present in the gastric wall; "tension" receptors, arranged in series and sensitive to contraction and elongation, and "stretch" receptors, arranged in parallel and sensitive to elongation only (3)(4)(5)(6).…”

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“…17 However, application of this stimulus is limited by a decrease in the rate of TLOSRs during prolonged gastric distension. 17,18 This suggests adaptation to prolonged distension. These findings demonstrate that this type of stimulus should not be used in sequential experimental conditions.…”