Receptive relaxation of the stomach by feeding was studied in 5 conscious dogs by means of chronically implanted force transducers on the gastric body and antrum.
It was found that only the gastric body but not antrum relaxed by feeding, and magnitude of the relaxation of the gastric body was linearly related to the volume (5, 10 and 20 g/kg) of test meals, given once or in multiple times.
Secondly, in the study of pharmacological blockers, it was found that atropine, hexamethonium and phentolarnine significantly inhibited relaxation, while naloxone and proglumide significantly suppressed relaxation in 3 dogs. Propranolol and domperidone did not influence on receptive relaxation.
It is concluded that receptive relaxation of the stomach is mainly mediated through a cholinergic reflex, however, invlovement of neurotransmitters other than acetlycholine is suggested in the regulation of receptive relaxation.

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Morphological specializations of smooth muscles from the middle part of the cat ureter have been examined by electron microscopy using thin sections and freeze-fracture replicas.
It is notable that there were many gap junctions which were characteristic in being formed on the surface of blunt cytoplasmic projections protruded from each neighboring cells. In addition to gap junctions, there were two other different junctions, i.e, intermediate junctions and “focal attachments”. The latter represents the cell attachment in which two apposing plasma membranes are attached to each other without the intervension of basal lamina in the narrow intercellular space.
Caveolae were lined in rows which were intervened by dense band zones parallel to the long axis of the muscle fibre as seen by freeze-fracture replica. Gap junctions were noted to be localized within or along the caveolar zones, being elliptical in shape with the long axis parallel to muscle fibres. As observed in thin sections, gap junctions in freeze-fracture replicas were noted on the top of cytoplasmic protrusions. No membrane specializations were observed in freeze-fracture replicas which corresponded to the “focal attachment” or intermediate junction as seen in thin sections.
As to the innervation, the autonomic nerve terminals were in abundance, closely apposed to the smooth muscles. In addition to autonomic nerve terminals, sensory nerve terminals were observed between muscle fibres, consisting of axon terminals and lamellar cells, the same structure as mechanoreceptive lamellar corpuscles known in other organs.

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In the examination of gastric emptying using radioisotopic techniques, three areas of interest were established, i.e. the entire gastric, proximal gastric and antral area, and gastric emptying abnormalities in cases of gastric and duodenal ulcers and their mechanism were studied by analyzing gastric emptying curves obtained from these areas.
Results were summerized as follows:
1. In highly localized gastric ulcers at active stage, compared to healthy subjects, (1) gastric emptying in the entire gastric area was accelerated, (2) the movement of the contents from the proximal gastric area to the antral area was accelerated, and (3) the movement from the proximal to the antral was greater than that from the antral to the duodenum during the first three minutes after start of the measurement.
Hence, in highly localized gastric ulcers at active stage, it is believed that gastric emptying in the entire is accelerated as the movement from the proximal to the antral is accelerated.
2. In low localized gastric ulcers at active stage, compared to healthy subjects, (1) gastric emptying in the entire was not observed in the first minute and gastric emptying was delayed once it started, (2) the movement from the proximal to the antral was fast as in healthy subjects in the first 17 minutes or so, and (3) in the first seven minutes, the movement from the proximal to the antral was greater than that from the antral to the duodenum.
Hence, in low localized gastric ulcers at active stage, it is believed that gastric emptying in the entire becomes delayed as the gastric emptying activity in the antral is lowered.
3. In duodenal ulcers at active stage, compared to healthy subjects, (1) gastric emptying in the entire was accelerated, (2) the movement from the proximal to the antral was accelerated, and (3) during the measurement, the movement from the antral to the duodenum was greater than that from the proximal to the antral.
Hence, in duodenal ulcers at active stage, it is believed that gastric emptying in the entire is accelerated as gastric emptying ability of the entire becomes excited along with that in the proximal and antral.
4. At healing stage, gastric emptying was found to be closer to that of healthy subjects than at active stage.

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Nagase, H., Karaki, H. and Urakawa, N. The inhibitory effects of calmodulin antagonists on the endothelium-dependent relaxation in rabbit aorta . Japanese Journal of Smooth Muscle Research 1986, 22 (2), 97-102 .-Effects of trifluoperazine (TFP, 10^-5 M), trifluoperazine sulfoxide (TFP-SO, 10^-5 M), N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7, 10^-4 M), N-(6-aminohexyl)-1-naphthalenesulfonamide (W-5, 10^-4 M) and verapamil (10^-5 M) on the endothelium-dependent relaxation of the contractions induced in the isolated rabbit aorta were studied . Carbachol (10^-6-10^-5 M) and A23187 (10^-8 M) relaxed the contraction due to norepinephrine (10^-6 M) and histamine (10^-5 M) in the aorta with endothelium. TFP and W-7 completely inhibited the relaxation induced by carbachol and A23187. In contrast, TFP-SO and W-5, which have lower affinity to calmodulin, had little or no effect on either the carbachol- or A23187-induced relaxation . An organic calcium antagonist, verapamil, did not change the relaxation induced by carbachol or A23187. W-7 did not modify the relaxing effect of sodium nitroprusside (10^-8-10^-6 M) which is not mediated by endothelium. These results suggest that either formation or release of endoth -elium-derived relaxing factor involves the process mediated by calmodulin in the rabbit aorta.

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Manometric study was performed to investigate the effects of cisapride, a new nonantidopaminergic gastrointestinal prokinetic compound, on interdigestive lower esophageal sphincter pressure (LESP) and gastroduodenal motility using infused catheter technique. The subjects consisted of 9 healthy volunteers and 29 patients with progressive systemic sclerosis (19), reflux esophagitis (8) and others (2). 4 mg of cisapride was given by bolus injection, continuous infusion or oral administration.
The following results were obtained:
1) Intravenous and oral cisapride increased LESP compared with basal pressure. Especially, bolus injection of cisapride caused a significant elevation of LESP during 30 minutes after administration.
2) After administration of cisapride, gastroduodenal motility was accelerated gradually, then inducing IMC-like contractions. By bolus injection, IMC-like contractions were induced in healthy subjects more frequently than in patients group.On the other hand, motility index of stomach and duodenum showed persistent increase in patients group compared with healthy subjects.
3) Cisapride-induced IMC-like contractions initiated from LES and upper part of stomach and mediated to duodenum, though aborad migration was not confirmed in the present study.

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