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At least 163 records · Page 9Linked to original sources
PubMed1957

The effect of carrier strontium on the absorption of oral doses of radioactive strontium in rats.

Carrier strontium had relatively little effect on the retention of an oral dose of radioactive strontium by the rat when it was administered immediately after the radioactive dose. The proportion of the radioactive dose which was excreted in the urine, on the other hand, increased progressively with the carrier dose. There was a decreased uptake of radioactive strontium in rats fed on a special low strontium diet. The effects of dietary strontium are discussed. Evidence was found of a discrimination by the rat against strontium in favour of calcium which was accounted for, at least in part, by a preferential urinary excretion of strontium.

Animals↗
PubMed1957

The preservation of substance P by lysergic acid diethylamide.

Lysergic acid diethylamide (LSD) potentiated the response of guinea-pig ileum to substance P but not to histamine. It also inhibited the disappearance of substance P when incubated with guinea-pig brain extract but not when incubated with chymotrypsin. Eserine, morphine, mescaline, chlorpromazine, ergometrine, strychnine and 2 bromo-LSD did not have this effect. Oxytocin was not destroyed by brain extract. The inhibition of the destruction of substance P by LSD could be antagonized by 2 bromo-LSD. This effect of LSD may have some relation to its pharmacological actions.

Brain↗
PubMed1957

Inhibition by morphine of the release of acetylcholine from the intestine of the guinea-pig.

In experiments on the isolated small intestine of the guinea-pig, morphine inhibited the release of acetylcholine (ACh) into the bath fluid. Experimental evidence is presented which suggests that the reduced release of ACh could not be explained by an inhibition of the synthesis of ACh, nor by stabilization of the bound form of ACh in the tissue. Apparently morphine reduces the excitability of postganglionic structures and thereby the liberation of ACh from nerve endings during the process of excitation.

Acetylcholine↗
PubMed1957

The action of morphine and related substances on contraction and on acetylcholine output of coaxially stimulated guinea-pig ileum.

Morphine depresses the twitch and tetanus of stimulated guinea-pig ileum by reducing acetylcholine released from cholinergic nerve endings. Acetylcholine output per shock falls to roughly the same residual amount at varying stimulation rates. Since normal output per shock declines with increasing stimulus frequency, the proportionate effect of morphine diminishes as stimulus frequency rises. Acute "tolerance" to morphine and a state of "morphinedependence" can be produced. Phenadoxone, dihydromorphinone, metopon, methadone, and heroin are more active, codeine and pethidine less active, than morphine. Nalorphine also depresses the twitch and can desensitize the gut both to itself and to morphine.

Acetylcholine↗
PubMed1958

The effect of drugs on spontaneous motility and on response to stimulation of the extrinsic nerves of the gut of a teleostean fish.

Trout gut shows, in addition to changes in general muscle tone, longitudinal "pendular" rhythms, peristaltic waves, and longitudinal "colic" contractions. Both vagus and splanchnic nerves are motor and there is no evidence of antagonistic "sympathetic" and "parasympathetic" nervous control. A posterior autonomic nerve supplying the rectum stimulated or inhibited according to the duration and frequency of the electrical pulses applied. Acetylcholine increased the tone and amplitude of pendular movements in all regions of the gut, and produced strong contraction of the circular muscles. Both nicotine and hexamethonium antagonized the action of acetylcholine, suggesting that its principal site of action is the neurone. Adrenaline lowered the tone of the longitudinal muscle and abolished pendular activity in the intestine and rectum, but contracted the longitudinal and circular muscles of the stomach. Hexamethonium bromide abolished peristalsis but greatly increased the amplitude of pendular contractions.The reaction of the trout intestine to both histamine and pilocarpine was slight, but nicotine, 5-hydroxytryptamine, eserine, and barium caused strong contractions. The actions of atropine and piperoxan (933F) are discussed. Evidence is presented which suggests that the postganglionic vagus nerve fibres supplying the trout stomach may be adrenergic, while both the splanchnic nerve fibres to the stomach and intestine, and the preganglionic vagal fibres to the stomach, may be cholinergic. It is also suggested that there is a continuous release of acetylcholine by cholinergic neurones in the gut wall.

Acetylcholine↗
PubMed1958

The effect of cooling and of 5-hydroxytryptamine on the peristaltic reflex of the isolated guinea-pig ileum.

Cooling the guinea-pig ileum to 19 to 26 degrees abolished the emptying phase of the peristaltic reflex. The effects of cooling to 10 degrees were usually reversible, but cooling to 5 degrees for 3 to 8 hr. produced an irreversible decrease in or abolition of the emptying phase. 5-Hydroxytryptamine (5-HT) added in low concentrations to the fluid outside the intestine restored slight peristaltic activity after this activity had been abolished by cooling. If the peristalsis had been depressed but not abolished by cooling, 5-HT in the bath sometimes abolished it. 5-HT introduced into the lumen of the cooled gut regularly restored or increased peristaltic activity. This action was prevented by previous injection of 2-bromolysergic acid diethylamide into the lumen. It is suggested that, when introduced into the lumen, 5-HT may sensitize the sensory receptors in the mucosa of the cooled intestine. When applied outside, 5-HT may facilitate transmission at synapses involved in the peristaltic reflex arc, the excitability of which has been depressed by cooling.

Cold Temperature↗
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↗