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

Abstract

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.

The Role of Central and Enteric Nervous Systems in the Control of the Retrograde Giant Contraction

“…Interruption of either CNS or ENS innervation of segments of the small intestine did not block the orad progression or velocity of the RGC across the entire small intestine. This finding corroborates prior studies, 5,10 and suggests that the extrinsic innervation, ie, the vagus nerves through the mesenteric nerves, 5,6 control orad propagation of the RGC across the small intestine. However, other findings in this study demonstrate that this conclusion is incomplete.…”

“…The primacy of the CNS in the control of the RGC was investigated by sectioning the jejuno-ileum into 3 equal length segments and re-anastomosing them such that the segments were out of normal order. This surgery preserved activation of the normal propagation sequence of the RGC, 10 suggesting that the RGC is controlled in a point by point manner by the CNS through the mesenteric nerves with little or no input from the ENS. On the other hand, Gregory 11 indicates that the ENS does have a role in this process as the RGC is not observed in short Thiry-Vella loops of proximal jejunum during vomiting.…”

“…The primary differences between these studies were the length of intestine surgically manipulated and the length over which the RGC response was recorded. In one case 10 intestinal segments of about 100 cm long with 2 recording sites were used, whereas in the other 11 intestinal segments of about 15 cm long with one recording site were used. These studies suggest that while the CNS controls the RGC over the entire small intestine, the ENS participates in the local control over the RGC.…”

Effects of acupuncture on vasopressin-induced emesis in conscious dogs

“…Apomorphine infusion also caused retrograde giant contractions, which started from the mid-small intestine in conscious dogs (29,36). Vomiting was observed, followed by strong antral contractions induced by apomorphine (36).…”

Emesis in dogs: a review

“…UES: Upper oesophageal sphincter. Summarised from: ( Abe and others 1993 [2b], Abe and others 1994 [2b], Furukawa and Okada 1994 [2b], Koga and others 1998 [2b], Koga and Fukuda 1990 [2b], Lang and others 1986b [2b], Lang and others 1986a [2b], Lang and others 1993 [2b], Lang and others 2002 [2b], Onishi and others 2007 [2b], Sha and others 1996 [2b]). [OEG C.]…”