Spontaneously developed tension (active tone) and intracellular Ca²⁺ level of aortae from spontaneously hypertensive rats (SHR), stroke-prone SHR (SHRSP), malignant SHRSP (M-SHRSP) and control Wistar Kyoto rats (WKY) were compared. Systolic blood pressure of WKY, SHR, SHRSP and M-SHRSP was 130mmHg, 200mmHg, 250mmHg and 260mmHg, respectively. Preparations from all strains of spontaneously hypertensive rats exhibited active tone which was abolished by the removal of extracellular Ca²⁺ or by the application of verapamil. The active tone was greater in the order of aortae from SHR<SHRSP<M-SHRSP. Intracellular Ca²⁺ level measured by Fura-2 method decreased by the removal of extracellular Ca²⁺. The degree of the decrease was greater as the blood pressure of the rats increased, indicating the greater elevation of intracellular Ca²⁺ level in the presence of extracellular Ca²⁺. A correlation was obtained between the active tone, intracellular Ca²⁺ level and blood pressure. Thus, it was demonstrated that the development of the active tone is brought about by the changes in Ca²⁺ influx of smooth muscle cell membrane and the degree of the change is positively related to the degree of hypertension.

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Effect of T-1815, a new colonic prokinetic compound, on gastrointestinal motility was studied in anesthetized and conscious dogs fasted for 24 hr before experiment. In anesthetized dogs, intravenous injection of T-1815 in doses of 0.3-3.0 mg/kg caused a biphasic effect on the gastric motility, a slight decrease followed by a slight increase. While the compound elicited only an increase in motility of the duodenum, jejunum and colon. In the colon, high-amplitude contractions were observed in 2 out of 5 animals at 1 mg/kg, i.v. of T-1815 and 4 out of 5 animals at 3 mg/kg. Bethanechol at 0.01 mg/kg, i.v. produced only a potentiation of the motility in all of the sites, but never induced high-amplitude contractions in the colon. During the interdigestive state in conscious dogs, intravenous T-1815 at 1 and 3 mg/kg caused contractions similar to the interdigestive phase III contractions at the stomach and duodenum in only 2 out of 7 experiments, and colonic motility was slightly depressed at 3 mg/kg. Oral administration of T-1815 at 30 and 50 mg/kg did not elicit the phase III-like contractions but produced persistent contractions at the stomach and duodenum in 2 out of 4 conscious animals during the interdigestive state. In the proximal and middle colon, high-amplitude contractions were observed in 5 out of 7 animals by 10-50 mg/kg, p.o. of T-1815. From the above results, it is concluded that the pharmacological effect of T-1815 on gastrointestinal motility is different from that of the cholinergic agonist. In addition, T-1815 seems to have a characteristic to induce high-amplitude contractions which are known to be closely related to defecation.

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We evaluated interdigestive moter patterns in the allotransplanted small bowel, in comparison with orthotropic allotransplanted canine jejunoileum and orthotropicaly autotransplanted canine jejunoileum or intact ones by using strain gage force transducers which were sewn to the serosal surfaces of the duodenum, jejunum and ileum.
Interdigestive intestinal motility of each conscious dogs was recorded at 2 weeks, 4 weeks and 8 weeks after each operation.
1. No significant differences were recognized on the mean durations of Interdigestive migrating confractions (IMC) of the duodenum among three groups.
2. Interdigestive migrating contractions (IMC) appeared at the autotransplanted jejunoileum with shorter duration than duodenum, and lacked of coordination between the intact duodenum and the transplanted jejunoileum for at least 8 weeks after the operation.
3. IMC also appeared at the allotransplanted jejunoileum with shorter duration than duodenum and lacked of coordination between the intact duodenum and the transplanted jejunoileum for at least 8 weeks after the operation. These charactristic moter patterns were similar to those of autotransplanted dogs.
These observations suggest that intrinsic nervous system, believed to be important for initiation of the IMC of small bowel, were preserved even in the allotransplanted small bowel. Thereafter, effective immunosupression must allow small bowel allotransplantation to become clinical reality.

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