Pharmacological Studies on the Autonomic Nerves of the Small Intestine of the Horse. I. Sympathetic Innervation of the Small Intestine.

In 1940 Tanaka and Ohkuho observed a marked contraction in isolated strips of horse ileum after the addition of adrenaline to the bath. This observation was confirmed and the effects of acetylcholine, histamine, and posterior pituitary extract studied in a similar manner (Alexander, 1949). It was found that acetylcholine and histamine caused a marked rise in tone and increased the magnitude of the rhythmic contractions, whereas the posterior pituitary extract was without effect. In other experiments with isolated blood-perfused ileum, similar responses were evoked with acetylcholine and histamine, whereas adrenaline inhibited motility and posterior pituitary extract caused a small contraction (Alexander, 1949). The experiments described here were designed to determine the response of the ileum in the living animal to adrenaline, carbamylcholine, histamine, and posterior pituitary extract. M ETHODSObservations were made on three ponies with Biebl loops and one with a Thiry-Vella fistula. The surgical techniques involved in the preparation of Biebl and Thiry-Vella loops in the horse are described elsewhere (Alexander, 1951).Recordings of movement in the Biebl loop were made with the double tambour system described by Douglas and Mann (1941) and from the Thiry-Vella loop by a balloon and water manometer.Variations in the intestinal temperature were measured with two thermocouples and a galvanometer. The thermocouples were made from junctions of copper and eureka wire.The reference couple was placed in a vacuum flask containing water at about 370 C., along with a thermometer; the second couple was stitched through the exteriorized intestine so that the junction lay in or against the mucosa. A calibration curve for the galvanometer was constructed by plotting measured temperature differences between the two thermocouples against the galvanometer deflection produced. Thus it was possible, by reading simultaneously the galvanometer deflection and the temperature of the reference couple, to determine the temperature of the couple in the intestinal mucosa.Aqueous solutions of adrenaline hydrochloride, carbamylcholine, ,histamine acid phosphate, and posterior pituitary extract were injected intravenously. The doses given were the least which consistently produced a measurable response; doubling this dose produced a similar but more lasting effect (Table I). It was considered unfair to subject the animals to undue distress by further increase of dosage. The effect of each drug was tested at least four times on each pony.

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Action Des Précurseurs Et Des Métabolites des Catécholamines Sur La Motricité Du Duodénum Isolé De Rat Référence particulière à la dopamine

Miachon

Peyrin

Cier

1979

Archives Internationales de Physiologie et de Biochimie

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Studying the effects, on the isolated rat duodenum motricity, of ten compounds precursors or metabolites of catecholamines, the following results were obtained: The direct metabolites of epinephrine and norepinephrine (metanephrine, normetanephrine), are either ineffective at concentrations below 5 X 10(-6) M, or weakly inhibitory at higher concentrations. Such inhibitory effects are prevented by alpha- and beta-blockers. 3-methoxy, 4-hydroxyphenylglycol and vanylmandelic acid have no significant effect. The catecholamine precursor, dopamine, the related compounds DOPA, 3 methoxytyramine, and to a lesser extent, 3-O methyl DOPA and homovanillic acid, have excito-motor effects at concentrations ranging mainly from 10(-7) M to 10(-5) M. At higher concentrations, the same compounds frequently exhibit inhibitory effects. The excito-motor effects might be due to a serotoninergic mechanism, since they are suppressed by the serotoninergic blocking agents methysergide and cyproheptadine. Furthermore, in the case of DOPA, we were able to establish a relationship between the excito-motor effects and duodenal serotonin stores. As for the inhibitory effects, they may be prevented by using alpha and beta blocking agents. Dihydroxyphenylacetic acid has no effect on the isolated rat duodenum motricity. The fact that dopamine and related compounds may have excitomotor effects at some concentrations, correlated with some physiopathological observations in man and animal allows some considerations about the eventual role of dopamine on intestinal motricity.

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Pharmacological Studies on the Autonomic Nerves of the Small Intestine of the Horse. I. Sympathetic Innervation of the Small Intestine.

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Systemic Pharmacology of Adrenergic Agonists and Antagonists: Effects on the Digestive System

Systemic Pharmacology of Adrenergic Agonists and Antagonists: Effects on the Digestive System

The Effects of Some Humoral Agents on the Horse Ileum

Action Des Précurseurs Et Des Métabolites des Catécholamines Sur La Motricité Du Duodénum Isolé De Rat Référence particulière à la dopamine

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