Mitsuo Nakaya

Inhibition of Interdigestive Contractile Activity in the Stomach by Peptide YY in Heidenhain Pouch Dogs

The inhibitory effect of peptide YY on contractile activity in the innervated main stomach and the vagally denervated fundic pouch in conscious Heidenhain pouch dogs was investigated. Peptide YY was given in i.v. bolus injections of doses between 12.5 and 100 pmol/kg body wt. During the digestive state, 2-3 h after feeding, peptide YY was found to have no effect on contractile activity in either the innervated or the vagally denervated stomach. In the interdigestive state, it was found that peptide YY inhibited the interdigestive migrating contractions in the innervated main stomach dose-dependently for 1.2 +/- 0.1 to 5.8 +/- 0.3 min, but did not affect pouch contractions at all. This peptide, however, did not influence the cycle of the interdigestive migrating contractions. Pentagastrin, on the other hand, suppressed the interdigestive migrating contractions in the innervated main stomach when the bolus doses were greater than 300 pmol/kg body wt, but did not inhibit pouch contractions completely with this dose. Atropine (0.05 mg/kg body wt) suppressed contractions in both the main stomach and the vagally denervated pouch. Peptide YY inhibits the interdigestive migrating contractions in the stomach through the extrinsic nerves.

Interdigestive Gallbladder Bile Concentration in Relation to Periodic Contraction of Gallbladder in the Dog

Interdigestive changes in the concentration of bilirubin and sodium in gallbladder bile collected through a chronically indwelling tube in the gallbladder were measured in conjunction with periodic contractions of the gallbladder and immunoreactive motilin concentration in plasma in conscious dogs. It was found that the bilirubin concentration in the gallbladder bile increased as stepped arcs that show periodic decreases with each cycle of the interdigestive migrating contraction in the stomach. The cycle for bilirubin concentration was then repeated, with higher maximum bilirubin values occurring during successive interdigestive migrating contractions cycles. In contrast, the sodium concentration did not progressively increase but fluctuated widely in association with changes in the bilirubin concentration. Peaks in the concentration of bilirubin and sodium generally coincided and occurred in the phase 3 period of the interdigestive migrating contractions in the stomach and the duodenum. However, the initial rise in the sodium concentration after the fall took place earlier than that in the bilirubin concentration in almost one-half of all experiments. Peaks of plasma immunoreactive motilin concentration coincided with the maximum concentration of gallbladder bile in each of the concentrating cycles, but there was no correlation between the two when compared over the entire period of the experiments. These findings suggest that the interdigestive periodic contractions in the gallbladder may play a role in the progressive concentration of bilirubin in gall bladder bile; that is, gallbladder relaxation after termination of the immunoreactive motilin concentration may be associated with aspiration by the gallbladder of dilute hepatic bile. This may in turn stimulate further gallbladder reabsorption. These studies do not allow firm conclusions to be drawn regarding the role of motilin in gallbladder absorption.

Neurohormonal control of gastrointestinal motor activity in conscious dogs

Interdigestive migrating contractions (IMC) were analyzed for their occurrence interval, duration, migrating velocity, and frequently in long term records obtained by means of chronically implanted force transducers in the main stomach and the extrinsically denervated fundic pouches or in the intact jejunum and the extrinsically denervated Thirty loop in 10 conscious dogs. Plasma immunoreactive motilin (IRM) was measured simultaneously. It was found that concomitant occurrence of IMC in the main stomach and pouch was closely associated with increase in plasma IRM concentration. On the other hand, in the extrinsically denervated jejunal loop, IMC-like contractions occurred independently of and more frequently than those in the intact jejunum and did not correlate with an increase in IRM concentration. It is concluded that gastric motor activity is under humoral control but in the jejunum, autoregulation by the intrinsic nerve plexus is more predominant than humoral factor(s).

Does motilin control interdigestive pepsin secretion in the dog

Pepsin output in the Heidenhain pouch, plasma motilin concentration, and contractile activity in the pouch and the main stomach were investigated in five dogs. During the interdigestive state, the pepsin output was significantly increased with a cyclic increase in contractile activity in both the pouch and main stomach at approximately 100-min intervals. The plasma immunoreactive motilin (IRM) concentration fluctuated during the interdigestive state, and, peaks of IRM concentration coincided with the maximum pepsin secretory activity. Exogenous administration of motilin (0.5 micrograms/kg-hr) increased contractile activity in the main stomach and pouch quite similar to the natural interdigestive migrating contractions (IMC), and increased pepsin output significantly. Atropine pre-treatment suppressed the naturally-occurring and motilin-induced pepsin output and contractions in the pouch. It is concluded that pepsin output and contractions in the Heidenhain pouch increase in close association with the IMC in the main stomach during the interdigestive state and these cyclic motor and secretory events in the vagally denervated fundic pouch are most likely regulated by motilin through the intramural cholinergic pathway.

Regulation of interdigestive contractions in the denervated stomach

SummaryThe effects of thiopental sodium on the regulation of interdigestive migrating contractions (IMC) in the stomach were investigated in dogs with extrinsically denervated fundic pouches.During the interdigestive state, strong phasic contractions in the pouch took place consistently in accordance with the IMC in the main stomach. The cyclic increase in plasma motilin concentration was more closely correlated with the increase in contractile activity in the pouch than the increase in the main stomach. General anesthesia by thiopental sodium promptly inhibited the IMC in the main stomach but the contractile activity in the pouch was not affected but gradually decreased in proportion to the decrease in plasma motilin concentration.In conclusion, contractile activity in the extrinsically denervated pouch, which is quite independent of the CNS, is directly controlled by a humoral factor(s), motilin. However, interdigestive motor activity in the extrinsically intact stomach appears to be regulated by the CNS as well as peripheral circulation humoral factors.

Effect of proglumide on gastrointestinal motility and gastric secretion in the conscious state

Proglumide suppressed neither phase III activity nor propagation of interdigestive migrating contractions (IMC) in the gastrointestinal tract. Furthermore, proglumide did not inhibit the gastric motor activity stimulated by pentagastrin, however, it suppressed the pH in Pavlov pouch stimulated by pentagastrin in the interdigestive state. On the contrary, in the digestive state, proglumide did not suppress the pH. That might be due to not only various gut hormones including gastrin, but also neural stimulation, mechanical stimulation and so on. In conclusion, antigastrin effect of proglumide is rather remarkable on the acid secretion not on the gastrointestinal motor activity. Proglumide may be an antacid without suppression of motor activity.