Pyloric motility and liquid gastric emptying during barostatic control of gastric pressure in pigs.

Abstract

1. In conscious pigs, intragastric pressure was controlled by a water barostat such that the gastroduodenal pressure gradient was always positive with the barostat set above 15 cm. In six pigs pyloric motor function was removed by prior pylorectomy. 2. In pylorus-intact animals, isolated pyloric pressure waves (IPPWs) occurred at a median of 2-9 min1 during duodenal dextrose infusion with the barostat set at or above a threshold of 15 cm. Increases of intragastric pressure above this threshold had no additional effect upon rates of IPPWs. Below this threshold, with identical duodenal dextrose infusion, IPPWs occurred infrequently (0 5 min'). In pylorus-excised animals virtually no IPPWs were seen. 3. In both pylorus-intact and -excised animals, the rate of antral pressure waves (APWs) was dependent upon intragastic pressure during duodenal infusion of both saline and dextrose. No threshold for stimulation was seen. Duodenal dextrose infusion inhibited APWs in pylorus-intact animals only. 4. With a positive gastroduodenal pressure gradient, gastric emptying was more rapid in pylorus-excised animals than pylorus-intact animals during duodenal dextrose infusion. In contrast, gastric emptying rates were not different between pylorus-intact and -excised animals during saline infusion. 5. These findings suggest an all-or-none-type stimulation of localized pyloric contractions by distension of the stomach beyond a threshold, in synergism with stimulation by nutrients within the upper small bowel. In contrast, stimulation of antral motility is in proportion to distension of the stomach. The pylorus, by way of localized pyloric contractions, is an effective resistor to transpyloric flow in the face of a positive gastroduodenal pressure gradient.

Influence of jejunal nutrients on transpyloric flow and pyloric resistance in pigs

“…In our study, their uneffectiveness in reducing gastric emptying might be related to the presence of the fundic barostat that maintained the fundic pressure, thus avoiding the possible fundic distension generated by the inhibition of gastric emptying (Fone et al, 1990;Edelbroek et al, 1993). The linear relationship, found in conscious pigs, between the frequency of IPPWs and the degree of gastric distension strongly supports this view (Treacy et al, 1994). …”

Effect of pyloroplasty and fundectomy on the delay of gastric emptying and gastrointestinal transit of liquid elicited by acute blood volume expansion in awake rats

“…The role of the pylorus in GE control is still obscure. However, the pylorus has been proposed as an effective resistance to transpyloric flow of liquid by increased localized pyloric contractions (18), and delays in GE due to changes in pyloric pressure waves, obstructing the flow through the pylorus, have also been reported (19). Pyloric resistance was not essential to trigger the effect of BV expansion on GE, in contrast to previous results in anesthetized animals, which clearly demonstrated its participation (16).…”

Involvement of NO in gastric emptying of semi‐solid meal in conscious pigs

“…Indeed, the two opposite forces controlling emptying, namely propulsion and resistance, 9 both are increased by NOS inhibition. On the one hand, NOS inhibitors decreased fundic compliance and impaired meal related fundic relaxation, 10, 11 all of which resulting in an increased intragastric pressure which is primarily responsible for emptying of liquids 12 . On the other hand, NOS inhibitors increased pyloric tone 3 and the frequency of duodenal contractions 7 that contribute to pyloric and duodenal resistances, respectively 13 …”