Responses of the gastric musculature of the sheep to some humoral agents and related substances

Abstract

The number of published papers dealing with the pharmacology of the ruminant stomach is still small. An approach was made to the subject by Wester (1926), and later work includes that of Amadon (1930), Dougherty (1942) and the South African group, Quin & van der Wath (1938), Quin & Clark (1946 and Clark (1950a). The effects of choline esters and adrenaline were studied by Brunaud, Dussardier & Labouche (1950) and Brunaud & Dussardier (1951, 1953. The subject was reviewed by Clark (1950b). Except by Brunaud et al. (1950) most attention so far has been given to the responses of the rumen, and for this reason an extension of study to other parts of the stomach was needed.Because the work described here was done primarily as part of a wider study of gastric motility in the sheep, only those substances were studied which are believed to take part in the transmission of nerve impulses and to act as local hormones. Observations were also made on surviving gastric musculature in vitro. MATERIAL AND METHODSExperiments wita sheep. Scottish Blackface wethers were provided with ruminal and abomasal cannulae, usually of the ebonite type as described by Phillipson & Innes (1939), and were trained to stand quietly in a metabolism crate. Gastric motility was transmitted to air-filled rubber balloons and water manometers, pressure changes being recorded on a smoked paper. The ruminal cannulae had an internal diameter ofabout 2 cm And allowed simultaneous recording from balloons in the reticulum and rumen. The polythene tube connecting the reticulum balloon to the manometer system was supported by a stiff wire bent to allow the balloon to be passed through the rumino-reticular orifice. The rumen balloon was placed in the dorsal sac within a short distance of the cannula. A more sensitive, thin rubber balloon was preferred for the abomasum and this was placed in the mid-region of the organ. Two manometers were used and simultaneous records were made from any two of the three sites described.The average weight of the sheep was 30 kg. Each substance was given to at least six sheep, and usually at least 48 hr elapsed between successive experiments on one sheep. Four sheep were used for pharmacological experiments after bilateral thoracic vagotomy, combined in three with bilateral splanchnic section; the history of these sheep has been given in an earlier paper (Duncan, 1953). One adrenalectomized ewe was made available by Mr J. V. R. Evans. Two sheep and a goat were used for acute experiments during which they were anaesthetized with sodium pentobarbitone.

Inhibitory and excitatory effects of sympathomimetic amines on muscle strips from the stomach of the guinea‐pig

“…Similar responses have been recorded from the stomach of the guinea-pig, rat, rabbit and dog (Smith, 1918;McSwiney & Brown, 1926;Lange, 1955;Offermeier, 1966;Ehrreich & Furchgott, 1968;Guimaraes, 1969;Innes & Kohli, 1969); from human stomach (Haffner, Liavag & Setekleiv, 1969) and from ruminant stomach (Duncan, 1954;Sanford, 1968;Titchen, 1968 ; Van Miert & Huisman, 1968). Oesophageal smooth muscle from the cat also contracts in response to sympathomimetic amines (Christensen & Daniel, 1966.…”

IN VITRO SPONTANEOUS MOTILITY OF GASTRIC SMOOTH MUSCLES OF THE SHEEP

“…This spontaneous contractile activity was facilitated by, but not dependent upon, cholinergic mechanisms in all tissues except the omasal leaves. Whereas previous workers have had difficulty in obtaining spontaneously active strips of reticulum and rumen muscle (Dussardier & Navarro, 1953;Duncan, 1954;Stoyanov, Loukanov, Vassileva & Vassilev, 1976) we regularly obtained active strips especially when 100 % 02 gas was used. Increasing the 02 supply to isolated smooth muscle increases its activity in our preparations.…”

“…In experiments involving vagotomy in the conscious animal it was observed that a partial return of motility of the reticulo-rumen occurred over a period of 1-3 weeks following vagotomy (Duncan, 1953;Ruckebusch, Tsiamitas & Bueno, 1972) and in a recent study of this phenomenon, Gregory (1982) has suggested that it is an intrinsic cholinergic motility dependent upon the activity of the myenteric plexus. Attempts to demonstrate an intrinsic activity of the reticulum and rumen in vitro have met with varying success, particularly in the case of the reticulum which has proved to be refractory and less responsive than the rumen to parasympathomimetic and sympathomimetic agents (Dussardier & Navarro, 1953;Duncan, 1954;Sanford, 1961).…”

H1‐ AND H2‐RECEPTORS IN THE SMOOTH MUSCLE OF THE RUMINANT STOMACH

“…We determined the pA2 value by the method of Schild (2 min contact; Schild, 1947). Furthermore, the values may be complicated by the fact that we could determine the pA2 value for mepyramine only when the H2-receptor was already blocked by metiamide and the pA2 value for Rumen (LM) Reticulum ( (Duncan, 1954;Sanford, 1961). The difference in the histamine-induced response between our results and those of the workers might be explained by differences in the preparation used (LM, CM or stomach wall), or a different distribution of H1-and H2-receptors on the smooth muscles.…”

“…In sharp contrast, in the ruminants, it has been reported that intravenous administration of histamine causes paralysis of rumino-reticular motility and inhibition of eructation (Dougherty, 1942a;Clark, 1950;Duncan, 1954). Furthermore, histamine produces a relaxation of the isolated smooth muscle from the rumen and abomasum but does not cause any apparent contraction (Duncan.…”