Extrinsic nervous control of retrograde giant contraction during vomiting in conscious dogs.

Neural mechanisms controlling retrograde giant contraction during vomiting were studied in six conscious dogs with implanted strain gauge force transducers. The small intestine was divided into proximal (P), middle (M), and distal (D) segments. These segments were transplanted on intact mesenteric neurovascular pedicles. In three dogs, M and D segments were interchanged (group A). In three dogs, P and M segments were interchanged (group B). Before transplantation, apomorphine-induced vomiting caused retrograde giant contractions, starting from the M segment and rapidly migrating to the stomach. However, in group A, even after recovery of interdigestive migrating contractions migration, retrograde giant contractions during vomiting always originated in the distally interchanged M segment and jumped to the P segment without migration to the D segment. In group B, the retrograde giant contraction always originated in the proximally interchanged M segment and successively occurred in the distally interchanged P segment. We conclude that origination and migration of retrograde giant contractions are extrinsically controlled. These motor events during vomiting are thought to be a specific motor function that does not exist in the lower small intestine, and retrograde giant contraction during vomiting may originate in the mid-small intestine.