Neural control of small intestinal giant migrating contractions

We investigated the neural mechanisms of control of giant migrating contractions (GMCs) in five conscious dogs. After control recordings, a Thiry-Vella loop was prepared from the middle segment, and the remaining two segments were reanastomosed. GMCs were stimulated by intravenous administration of fentanyl and erythromycin lactobionate, oral administration of loperamide and erythromycin stearate, and gastric or intraluminal administration of cider vinegar in the loop. In the intact state, the agents stimulated GMCs in all three segments, and they propagated uninterruptedly from the point of their origin to the terminal ileum. The propagation velocity of GMCs increased, whereas that of migrating motor complexes (MMCs) decreased distally. After Thiry-Vella loop formation, the agents stimulated GMCs independently in the three segments, and they propagated only to the end of the segment in which they started. In the intact small intestine, the GMCs produced ascending and descending inhibition of spontaneous phase II contractions but did not interrupt the caudad propagation of the ongoing MMC. After Thiry-Vella loop formation, the ascending inhibition was unaltered, but the descending inhibition occurred only in the segment containing the GMC. We conclude that the propagation of GMCs in the small intestine is controlled by the enteric nerves. The extrinsic nerves control the ascending inhibition produced by GMCs, whereas the enteric nerves control the descending inhibition.