The effects of GABA (γ-aminobutyric acid) and homotaurine (3-aminopropane sufonic acid) on propulsive activity of the isolated segment, and on lomgitudinal and circular muscle strips were investigated in the guinea-pig distal colon.
GABA (0.1 and 1 mM) inhibited spontaneous propulsive activity with a reduction of longitudinal tension of the segment. Homotaurine (1 mM) slightly inhibited spontaneous propulsive activity.
GABA (0.01-1 mM) relaxed both longitudinal and circular muscle strips. Homotaurine (1 mM) slightly relaxed cicular muscle strip.
Desensitization to GABA and homotaurine was observed.
The inhibitory effects of GABA on both muscle strips were abolished by tetrodotoxin or atropine, but not by bicuculline. Carbachol-induced contractions on both muscle strips were not influenced by GABA or homotaurine.
These results suggest that GABA-induced inhibition of propulsive activity in the isolated colonic segment may result from activation of GABAB receptor on the cholinergic neurones in the wall, which in turn leads to reduction of release of transmitter acetylcholine.

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HIGASHINO, H., SUZUKI, A., (the late) Che Su and Tony Jer-Fu LEE. Role of Endothelial cells in responses of Spontaneously Hypertensive Rat Mesenteric Arteries to Norepinephrine and Angiotensins. Japanese Journal of Smooth Muscle Research, 23 (6), 449-456, 1987-The role of endothelial cells in the constrictor and dilator responses of mesenteric arteries to infused drugs was evaluated. Fifteen- to seventeen-week-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) were used. Periarterial sympathetic nerve stimulation (PNS, 6 Hz, 30 sec) elicited greater pressor responses in SHR than WKY. Acetylcholine (ACh, 1.0 μM) lowered the perfusion pressure elevated by norepinephrine (NE, 0.1 μM) significantly more in SHR than WKY. Angiotensin I and II (AI and AII, 1.0nM) markedly potentiated the PNS-induced constriction in both animals. Collagenase perfusion (Type 1A, 2 mg/ml, 5ml/min intermittently, for 23 min) significantly diminished the ACh-induced dilation, indicative of endothelium destruction. However, it greatly increased the constrictor effect of NE and AI and AII in SHR and the potentiating effects of AI and AII on PNS-evoked constriction in both SHR and WKY, especially in SHR. These results suggest that, while endothelial cells mediate the dilator response to ACh, they are unnecessary for the constrictor and potentiating effects of NE, AI and AII and, in fact, counteract the latter two effects, particularly in the hypertensive rats. Furthermore, the endothelial cell functions promoting the effect of ACh or countering those of NE, AI and AII are in general greater in SHR than WKY.

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I investigated the significance of bile reflux, when vagotomy was done to stress ulcer, by means of measuring gastric ulcer inex, gastric pH and serum gastrin levels of rats. And in order to examine influence of alkali factor of bile, I measured gastric acid output and serum gastrin levels after alkali or acid solution was infused into the untreated rat's stomach.
Results were summarized as follows:
1. When I infused alkali solution into the untreated stomach, there was no significant change in serum gastrin level but gastric acid output was significantly accelerated, as compared with infusing acid solution.
On the other hand, when I infused alkali solution into the vagotomized stomach, serum gastrin level increased significantly and gastric acid output was significantly accelerated, as compared with infusing acid solution, so, acceleration of acid output observed when I infused alkali solution into the untreated stomach was not suppressed in spite of vagotomy operation.
2. In the vagotomized group, gastric acid output was significantly suppressed and serum gastrin level increased significantly as compared with the untreated group.But, when bile was led into the stomach in the vagotomized group, acid output was accelerated and serum gastrin level also showed a tendency to increase as compared with the group of vagotomy alone.
3. When mild stress was inflicted, stress ulcer formation was significantly prevented in the bile reflux group (vagotomy+pyloroplasty) as well as in the non-bile reflux group (vagotomy+pyloric ligation+gastroileostomy) if vagotomy was done. But, when severe stress was inflicted, stress ulcer formation was significantly prevented in the non-bile reflux group, but not prevented in the bile reflux group.
As mentioned above, it was proved that stress ulcer formation was not prevented under a severe stress, if bile reflux existed, even though vagotomy was done. So, if we do vagotomy operation, we need to choose the operation method not to induce bile reflux as much as possible.

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To elucidate the antral motor function after partial-transection, the author investigated the electromyographic change of the antrum before and after 1/3, 1/2, 2/3 partial-transection from the greater curvature or the lesser curvature at the lower third or the middle of the stomach.
The results were summarized as follows:
1. Over 1/2 of partial-transection from the lesser curvature or over 1/3 of partialtransection from the greater curvature at the lower third of the stomach, the remarkable prolongation of discharge intervals, the remarkable acceleration of propagation velocity and an appearance of antiperistaltic discharges were noted.
2. After 2/3 of partial-transection from the lesser curvature or over 1/2 of partialtransection from the greater curvature at the middle of the stomach, the slight prolongation of discharge intervals and the slight acceleration of propagation velocity were noted, however, an appearance of antiperistaltic discharges was recognized on the latter alone.
The above results suggested thatthepartial-transection at the lower third of the stomach rather than at the middle of the stomach or from the greater curvature rather than from the lesser curvature might effect on the antral motor function.

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