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At least 451 records · Page 25Linked to original sources
PubMed1958

The effect of substance P on the peristaltic reflex of the isolated guinea-pig ileum.

The introduction of substance P into the lumen of the isolated guinea-pig ileum caused an increase in the number and amplitude of the peristaltic waves. In preparations in which the peristaltic reflex was abolished, by fatigue, by external or internal application of 5-hydroxytryptamine, or by lowering the temperature of the bath, the introduction of substance P into the lumen of the intestine restored peristalsis. This effect of substance P was absent in preparations in which the mucous membrane was removed. Hexamethonium abolished the effect of substance P on peristalsis. It is concluded that substance P acts on the afferent nervous elements of the peristaltic reflex arc, possibly on the sensory receptors.

Central Nervous System↗
PubMed1959

The mechanism of the inhibition by carbonic acid of the smooth muscle contraction produced by histamine and oxytocin.

Carbonic acid inhibited the stimulating action of histamine on guinea-pig intestine and of oxytocin on the uterus of many animal species. This effect was relatively specific. Under the same conditions the actions of acetylcholine, KCl, adrenaline (on rabbit uterus), and ergot alkaloids were not inhibited. The electrical excitability of smooth muscle was similarly not affected. The inhibitory action of carbonic acid is directly proportional to its concentration in the medium in which the isolated organ is maintained. The study of the activity of histamine and oxytocin at different pH in a medium free of NaHCO(3) and buffered with a mixture of sodium maleate and maleic acid suggested that the inhibitory action exerted by carbonic acid was specific and independent of the simultaneous modifications of the hydrogen ion concentration. The mechanism of these phenomena is discussed.

Acetylcholine↗
PubMed1959

Effects of cross-suture and of injected acetylcholine on the supersensitivity of denervated striated muscle.

The sensitivity of the tongue muscles to acetylcholine was examined in repeated experiments on cats anaesthetized with hexobarbitone. The supersensitivity which developed after section of the hypoglossal nerve was found to decrease when the muscles, after cross-suture, became re-innervated from the vagus or the chorda-lingual nerve. The supersensitivity caused by denervation could also be reduced by injecting acetylcholine repeatedly during six hours in acute experiments.

Acetylcholine↗
PubMed1960

The effect of temperature on the direct muscle twitch response and the action of drugs on the isolated denervated rat diaphragm.

The effect of temperature on the direct twitch response of the normal and denervated rat diaphragm, and the sensitivity of the contractural response of the denervated muscle to acetylcholine, suxamethonium, decamethonium, and potassium salts, was studied. Cooling the normal diaphragm from 39 to 20 degrees increased the size of the direct twitch, but below this temperature the twitch response of the muscle was progressively depressed. The denervated muscle twitch was, by contrast, maximal at 39 degrees and decreases as the temperature was lowered. This property of the denervated muscle first appeared about the third day after denervation. The contractural response of the denervated diaphragm to applied acetylcholine was enhanced by cooling, while the response to potassium salts was depressed. The depression of the contracture induced by potassium followed closely the depression of the direct muscle twitch of the denervated muscle over the same temperature range.

Acetylcholine↗