Antral contractions

Erjdhromycin acts as a motilin receptor agonist (27-29). This mechanism may be at least partly responsible for the gastrointestinal adverse effects of macrolides. Clarithromycin may act on gastrointestinal motility in a similar way. In dogs, clarithromycin caused contractions and discomfort, as did erythromycin (30). In healthy volunteers, oral clarithromycin 250 mg bd caused a statistically significant increase in the number of postprandial antral contractions and antral motility (31). A single oral dose of clarithromycin 3000 mg resulted in severe abdominal pain within 1 hour of administration in two patients (32). 

Antral contractions (3 per min) are responsible for mixing and grinding of a solid meal into smaller particles (<5 mm) that can pass onto the duodenum. These antral contractions can easily be seen at ultrasonography. The contractions can be occlusive or non lumen-occlusive. An antral contraction is defined as an indentation of the gastric wall greater than one antral wall thickness, which is not due to respiration, pulsation transmitted from the aorta or heart, or to movements of adjacent intestine. 

Amplitude of antral contractions is measured as a fraction of relaxed area and the motility index is calculated as the amplitude multiplied by frequency. 

In the study by Hausken et al. (2002), in the pre-and postprandial period, a total of 44% of antral contractions were not detected by manometry, and only 1/5 of non-occluding contractions. 

Hveem et al. (2001) found that only 53% of antral contractions seen ultrasonographically had a temporally associated pressure event in the manometric reference channel. The lumen-occlusive contractions had, in 69%, an associated pressure event. Of the non-lumen-occlusive contractions, only 20% were associated with a pressure event. 

In about 50% of antral contractions observed by ultrasound, the corresponding pressure events are not identified in the manometric reference channel. This more than indicates that the knowledge of gastric mechanics, based solely on manometry, is at the least inadequate, missing almost half of the information given by ultrasound with regard to antral contractions. 

Hveem K, Sun WM, Hehhard G, Horowitz M, Doran S, Dent J (2001) Relationship between ultrasonically detected phasic antral contractions and antral pressure. Am J Physiol Gas-trointest Liver Physiol 281 G95-G101 Jang HS, Lee JS, Lim GY (2001) Correlation of color Doppler sonographic findings with pH measurements in gastroesophageal reflux in children. J Clin Ultrasound 29 212-217... 

Motilin is a neuropeptide expressed predominantly in the gastrointestinal tract that stimulates the contraction of gastrointestinal smooth muscle throughout the gut (Tonini 1996). Physiologically, its most characteristic role seems to be the induction of coordinated interdigestive antral and duodenal contractions (phase III of the migrating motor complex). The effects of motilin are both species and dose dependent. Motilin appears to have at least two receptors, one muscular and the other neuronal. Recent studies in vivo have emphasized the importance of the latter pathway and it is currently hypothesized that motilin acts on neurons in the myenteric plexus to release acetylcholine and other excitatory neurotransmitters. 

Similar contractile activity of motilin was observed in the isolated muscle strip of human gastric antrum and isolated myocytes [16]. Motilin (10 -10 M) caused concentration-dependent contractions of human antral muscle strips with an EC50 value of 1.4 x 10 M. Motilin caused concentration-dependent contractions of human antral myocytes with maximal contraction of 25.2% and an EC50... 

Fig. 12. Effects of EM574, porcine motilin, and cisapride on gastric antral motility after a semisolid meal. The meal was ingested within 5 min. EM574 and cisapride were administered intraduode-nally immediately after feeding. Motilin was infused intravenously during 30-min postprandial period. A representative pattern of interdigestive migrating complex (IMC) is shown in the inset to indicate the magnitude of contractions. (From Sato et al. [22] with permission from Elsevier Science.)...

Yamamoto, O., Matsunaga, Y, Haga, N., and Itoh, Z. (1994). Vagovagal inhibition of motilin-induced phase III contractions by antral acidification in dog stomach. Am. J. Physiol. USl, G129-134. 

Cholecystokinin (CCK) Enteroendocrine 1 cells, enteric nerves, others 1. Inhibits proximal gastric motility 2. Increases antral and pyloric contractions 3. Regulates nutrient-stimulated enzyme secretion and gallbladder contraction 4. Increases postprandial satiety 1. Oral nutrient ingestion 2. GGRP and bombesin from gut... 

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