Transmission Failure in Sympathetic Nerves Produced by Hemicholinium

The circular muscle strip is a new preparation for examining the action of drugs on the circular muscle of the guinea-pig isolated intestine. The preparation differed from the longitudinal muscle in that it was insensitive to drugs which act on autonomic effector tissues but, after inhibition of cholinesterase, it responded readily to choline esters, 5-hydroxytryptamine, histamine and nicotine. This behaviour necessitated the treatment of each strip with the anticholinesterase NN-diisopropylphosphodiamidic fluoride (mipafox) before each experiment. The contractions of the strip by 5-hydroxytryptamine, histamine and nicotine were abolished by procaine, botulinum toxin -Type A), morphine and hemicholinium, whilst the actions of acetylcholine and methacholine were unaffected. Contractions of the strip in response to each of the drugs were abolished by atropine and hyoscine. The action of nicotine was specifically antagonized by hexamethonium, that of 5-hydroxytryptamine by desensitization of the tissue to 5-hydroxytryptamine, and that of histamine either by desensitization of the tissue to histamine or by mepyramine. It is postulated that 5-hydroxytryptamine, histamine and nicotine stimulate specific receptor sites within the intramural nerve plexuses of the guinea-pig isolated ileum.Finally, botulinum toxin (Type A), morphine or hemicholinum, acting on the neuronal elements of the intramural plexuses, depressed the contractions of the circular muscle strip due to histamine or nicotine more readily than those due to 5-hydroxytryptamine.

Section: J Harrymentioning

confidence: 99%

The Action of Drugs on the Circular Muscle Strip From the Guinea‐pig Isolated Ileum

Harry

1963

“…Since hemicholinium is moderately active in blocking the hypogastric nerve (Chang & Rand, 1960) it was surprising to find that, in 5 experiments, this drug at levels of 1 x 10-4 had absolutely no effect on the response of the Finkleman preparation to stimulation of the periarterial nerves, even when allowed to act for periods of 45 min.…”

Section: I G a Bentleymentioning

confidence: 99%

Studies on Sympathetic Mechanisms in Isolated Intestinal and Vas Deferens Preparations

Bentley

1962

The effects of various drugs which block sympathetic nerves have been studied in Finkleman preparations of rabbit and cat ileum. Contractile responses could be produced in many cases after the normal inhibitory responses to periarterial nerve stimulation had been blocked. In almost all cases this contractile response was abolished by ganglion-blocking drugs. The normal rabbit ileum Finkleman preparation was found to behave differently towards bretylium than do preparations taken from animals treated with reserpine. The block of the guinea-pig isolated hypogastric vas deferens preparation caused by hemicholinium HC-3 was found to be reversed in the presence of noradrenaline, histamine, or 5-hydroxytryptamine, as was the block caused by guanethidine and bretylium. The results are discussed in relation to the Burn-Rand theory of sympathetic nerve mechanism.

“…Isolated atria from young cats with their sympathetic nerves attached were prepared as described by Chang &Rand (1960); in addition the vagus nerves were attached (Burn & Rand, 1958a).…”

Section: Methodsmentioning

confidence: 99%

Effect of Guanethidine in Revealing Cholinergic Sympathetic Fibres

Day

Rand

1961

Self Cite

Guanethidine abolished the inhibitory response of segments of rabbit intestine to stimulation of the sympathetic nerves which accompany the mesenteric arteries. In the majority of experiments a motor response of the intestinal segment was then revealed; it was more readily observed in intestinal segments from young than from adult rabbits. The motor response of the intestine to sympathetic stimulation after guanethidine was blocked by atropine. It was not blocked by hexamethonium and was present in rabbits in which the vagal innervation to the small intestine had been sectioned. In the cat isolated atria, guanethidine blocked the accelerator response to sympathetic nerve stimulation and revealed a response resembling that to stimulation of the vagus. It was concluded that guanethidine blocked the release of noradrenaline and thus revealed the response to the direct action of acetylcholine released from cholinergic sympathetic nerves.