Rectus Abdominis Preparation Research Articles

Neuromuscular effects and acute toxicity of an ethyl acetate extract of Spigelia anthelmia Linn.

An ethyl acetate extract of Spigelia anthelmia (EASa), with validated anthelmintic activity, was evaluated for its acute toxicity and general effects in albino Swiss mice and for neuromuscular relaxant activity in the frog sciatic-gastrocnemius and rectus abdominis preparation. The extract induced a dose-related myotonia and muscular paralysis of rapid onset at higher doses. The calculated LD50 after oral and intraperitoneal administration was 345.9 [241.4–484.7] mg/kg and 60.8 [47.4–80] mg/kg, respectively. In broilers, intramuscullar injection of EASa-induced spastic paralysis qualitatively similar to that obtained after succinylcholine administration and contrasting to the flaccid paralysis induced by d-tubocurarine. The contraction elicited by direct stimulation of the gastrocnemius was blocked by EASa by 54.3±4.7% (IC50 = 21.4 [11.2–35.8] μg/ml) and the twitches evoked by stimulation of the sciatic nerve were blocked by 69.1±7.4% (IC50 = 17.9 [4.5–34.23] μg/ml). EASa also blocked acetylcholine-induced contractions in the frog rectus abdominis by 58.6±7.4% (IC50 = 7.4 [1.7–15.28] μg/ml) but did not decrease tonic contractions induced by a high-potassium Ringer solution. In summary, the ethyl acetate extract of Spigelia anthelmia induces tonic paralysis in vivo, and decreases amplitudes of twitches and increases tonus of skeletal muscle in vitro.

Neuromuscular effects and acute toxicity of an ethyl acetate extract of Spigelia anthelmia Linn.

An ethyl acetate extract of Spigelia anthelmia (EASa), with validated anthelmintic activity, was evaluated for its acute toxicity and general effects in albino Swiss mice and for neuromuscular relaxant activity in the frog sciatic-gastrocnemius and rectus abdominis preparation. The extract induced a dose-related myotonia and muscular paralysis of rapid onset at higher doses. The calculated LD 50 after oral and intraperitoneal administration was 345.9 [241.4–484.7] mg/kg and 60.8 [47.4–80] mg/kg, respectively. In broilers, intramuscullar injection of EASa-induced spastic paralysis qualitatively similar to that obtained after succinylcholine administration and contrasting to the flaccid paralysis induced by d-tubocurarine. The contraction elicited by direct stimulation of the gastrocnemius was blocked by EASa by 54.3±4.7% (IC 50 = 21.4 [11.2–35.8] μg/ml) and the twitches evoked by stimulation of the sciatic nerve were blocked by 69.1±7.4% (IC 50 = 17.9 [4.5–34.23] μg/ml). EASa also blocked acetylcholine-induced contractions in the frog rectus abdominis by 58.6±7.4% (IC 50 = 7.4 [1.7–15.28] μg/ml) but did not decrease tonic contractions induced by a high-potassium Ringer solution. In summary, the ethyl acetate extract of Spigelia anthelmia induces tonic paralysis in vivo, and decreases amplitudes of twitches and increases tonus of skeletal muscle in vitro.

Neuromuscular blocking activity of a glycosidic extract of the plant Sarcolobus Globosus

Crude glycoside extracts from the plant, Sarcolobus globosus, were tested on the rat phrenic nerve-diaphragm, chick biventer cervicis and frog rectus abdominis preparations. Nerve-stimulated twitches were inhibited by the extract. The muscle paralysis was not similar to that by curare-like blockers as it was not reversed by neostigmine or by a tetanus. Although contractures to acetylcholine or carbachol were not affected by 0.6 mg/ml of the extract, higher concentration of the extracts (3 mg/ml) depressed the log dose-response curve of acetylcholine and carbachol. The results suggest that the neuromuscular blocking effect of the extracts is either dose-dependent or due to a mixture of toxins with presynaptic or postsynaptic actions.

Comparison of the skeletal muscle relaxant properties of Portulaca oleracea extracts with dantrolene sodium and methoxyverapamil

The effects of aqueous (AEE), dialysable (DIF) and methanol (MEE) extracts of Portulaca oleracea stems and leaves were compared with those of dantrolene sodium and methoxyverapamil (D-600) with respect to inhibition of twitch tension on the rat phrenic nerve-hemidiaphragm and with respect to contracture induced by nicotinic agonists on the frog rectus abdominis preparations. The extracts, dantrolene and D-600 inhibited twitch tension due to indirect electrical stimulation via the phrenic nerve (NS) on hemidiaphragm muscle, whereas the extracts and dantrolene inhibited, in addition, twitch amplitude due to direct muscle stimulation (MS). The extracts, dantrolene and D-600 also attenuated K + and caffeine-induced contractures with the extracts and D-600 also reducing the time taken for the K +induced contracture to fall to basal tension. In addition, the tetanic tension due to NS and MS was attenuated with only the extracts and dantrolene reducing the twitch/tetanus ratio (MS). There was a non-significant but consistent tendency for mutual potentiation between the extracts and dantrolene with respect to their inhibitory effect on twitch amplitude (MS) resulting in a shift to the left of the concentration-response curves to the extracts or dantrolene. This was not evident with the extracts and D-600 or dantrolene and D-600. Simultaneous addition of the extracts and dantrolene resulted in an increase in the rate of twitch tension inhibition and a decrease in the time to maximum relaxation of twitch amplitude (MS). The extracts and D-600 proved more effective in attenuating nicotinic agónist (acetylcholine, carbachol and nicotine)-induced contractures on the rectus abdominis muscle than dantrolene. From these observations, it appears that the Portulaca oleracea extracts mimic, in part, the effect of D-600 and dantrolene on the rat hemidiaphragm and frog rectus abdominis muscles; therefore, the muscle relaxant properties of the extracts may be due, in part, to inhibition of trans-membrane Ca influx, interference with the Ca-induced Ca release process and/or inhibition of the release of intracellular Ca from stores in the sarcoplasmic reticulum.

Acetylcholine and choline in common spices

AbstractAqueous extracts obtained from seven commonly used spices (cardamon, coriander, cumin, black pepper, red pepper, anise and fennel) showed cholinomimetic effects when tested on rat blood pressure, rat jejunum and frog rectus abdominis preparations. This effect was observed mostly when the spices were roasted. Chemical estimation using gas chromatography/mass spectrometry confirmed the presence of large amounts of acetylcholine and its precursor choline.

A comparison of the stimulant activities of oxotremorine analogues on the frog rectus abdominis and the guinea pig ileum

A series of tertiary amines structurally related to the potent muscarinic agent oxotremorine showed weak stimulant activity on the frog rectus abdominis preparation. The corresponding quaternary ammonium salts were more effective stimulants, the most potent being half as active as carbachol. The effects appeared to be due to direct stimulation of post-junctional nicotinic receptors. The relationship between the structures of these compounds and their ability to stimulate nicotinic receptors was compared with the structure-activity relationships in more conventional nicotinic stimulants. Finally, a comparison was made between the observed nicotinic potencies and previously published muscarinic potencies in the isolated guinea pig ileum. The tertiary amines were in general highly selective for muscarinic as opposed to nicotinic receptors, whereas the quaternary derivatives were only slightly more selective for muscarinic receptors than carbachol.

Effect of dithiothreitol on agonist and antagonist actions in frog muscle.

The effects of the disulphide bond reducing agent dithiothreitol (DTT) in the frog rectus abdominis preparation have been investigated. DTT, 1 mM, reduced the potency of the monoquaternary agonists acetylcholine, carbachol and tetramethylammonium and the response to electrical field stimulation; the same applied to nicotine, but the action of edrophonium was unaffected and that of the bisquaternary agonist, decamethonium, was increased. The potency of tubocurarine and gallamine as antagonists was unaltered or slightly reduced by DTT when monoquaternary agonists were used and increased when decamethonium was used as agonist. All these effects of DTT were reversed by the oxidizing agent 5-5'dithiobis(2-nitrobenzoic acid) and can be explained by a reduction of a disulphide bond in the vicinity of the anionic site of the nicotinic cholinoceptor. Comparison between these results and published data indicate that there are species differences between nicotinic cholinoceptors and motor endplates. In the guinea-pig ileum preparation DTT reduced the potency of nicotine acting at ganglionic nicotinic cholinoceptors, but had no effect on the agonist response mediated via muscarinic cholinoceptors.

Schistosoma mansoni: Species-selective response to N-chloroethyl-acetylcholine derivatives

Three new acetylcholine mustard analogs were tested on schislosome and vertebrate neuromuscular preparations. These compounds extend a previously reported structure-activity series. The new compounds investigated include isopropyl-, cyclohexyl-, and benzyl-2-acetoxyethyl-2′-chloroethylamine (PrM, ChM, and BzM). In schistosome motor activity studies, all of the compounds caused irreversible reductions in the activity of Schistosoma mansoni after 1 hr exposure followed by 19 hr in drug-free medium. Under nonlethal conditions of dosage and exposure time, all compounds blocked carbachol-induced paralysis, indicating a possible action at schistosome cholinergic sites. All the compounds also reduced the labeling of schistosomes by dimethylaminonapthalene-5-sulfonamidoethyl dimethylamine hydrochloride (DDNS), a fluorescent ACh analog. In isolated vertebrate tissue experiments, PrM and ChM had slight agonist activity in the guinea pig ileum, and only PrM had agonist activity in the frog rectus abdominis preparation. PrM and BzM were found to antagonize ACh responses in the guinea pig ileum. Exposure of vertebrate tissues for 1 hr to high concentrations of ChM caused no long-lasting inhibition of ACh, pilocarpine, and serotonin (5HT) responses. Histamine responses were slightly reduced from control. Following 1 hr exposure of vertebrate tissues to PrM, initial reductions in all responses were seen, followed by recoveries to near control. BzM treatment, however, reduced all responses far below control; the tissues did not recover even after washing for 2 hr. It is concluded that ChM and, to a lesser extent, PrM, had a greater effect on schistosomes than on vertebrate tissues. BzM did not display species selectivity in this favorable direction.

Lophotoxin: A neuromuscular acting toxin from the sea whip ( Lophogorgia rigida)

Lophotoxin, a compound isolated from corals of the genus Lophogorgia, produced paralysis and death when injected s.c. in mice ( ld 50 = 8.9 mg/kg ). In the isolated rat phrenic nerve-hemidiaphragm preparation, lophotoxin irreversibly abolished nerve-stimulated contraction but did not affect the contraction produced by direct stimulation of the muscle. In the frog rectus abdominis preparation, ACh-induced contractures were blocked by lophotoxin, but KCl-induced contractures were not affected. Though these findings do not exclude the possibility of a presynaptic action of lophotoxin on axons and/or nerve terminals, they do indicate that the toxin produces an irreversible postsynaptic blockade at the neuromuscular junction.

Neuromuscular Block of the Polymyxin Group of Antibiotics

The neuromuscular blocking effects of polymyxin and colistin were investigated in the unanesthetized rabbit, in the cat sciatic nerve–tibialis anterior muscle preparation in vivo, and in the frog rectus abdominis preparation in vitro. These antibiotics, along with certain others used for comparison, produced paralyses of different intensities in rabbits, depending on the dose, with no preceding fasciculation. In this regard, polymyxin was the most potent antibiotic studied. Polymyxin B sulfate (3–5mg/kg) and colistimethate sodium (60–90mg/kg) caused a blockade of neuromuscular transmission, partial paralysis of respiration, and hypotension in cats. The intraarterial injection of these antibiotics did not elicit muscle contraction; the response to the intraarterial injection of acetylcholine was reduced or abolished during the block; calcium and epinephrine antagonized the block; posttetanic potentiation occurred; edrophonium and decamethonium produced brief antagonism of the block; neostigmine, tetraethylammonium, and choline were without effect; and tubocurarine accentuated the block. During the block, muscle action potentials were reduced or abolished, and nerve action potentials were unaffected. (Response of the muscle to direct stimulation was reduced compared to the predrug response.) Both agents depressed muscle twitches elicited at the faster rate of stimulation (60/min) while the slow rate twitches (6/min) were hardly depressed. The serum ionic calcium level was not altered significantly by these antibiotics. Thus, the neuromuscular block displayed characteristics of a postsynaptic, nondepolarizing type that was noncompetitive in nature, with possible presynaptic elements and a depressant action on muscle fibers. Both polymyxin and oolistin possess transient ganglionic blocking action.

Pyrrolizidine alkaloids: actions on muscarinic receptors in the guinea-pig ileum.

1. Eleven pyrrolizidine alkaloids have been tested on the isolated guinea-pig ileum preparation.2. Platyphylline, supinine, heleurine and cynaustraline were more potent in antagonizing responses to acetylcholine and carbachol than responses to histamine. Their anticholinergic activity appeared to involve a competitive mechanism.3. Lasiocarpine, monocrotaline, spectabiline, sarracine, 7-angelylheliotridine, heliotrine and senecionine had similar antagonistic potencies against responses to both acetylcholine and histamine.4. The alkaloids had no appreciable activity as antagonists of acetylcholine in the isolated toad rectus abdominis preparation.5. These results are discussed with respect to interactions of the alkaloids at receptor sites involved in anticholinergic activity at the muscarinic receptor.

Neuromuscular pharmacology of oxotremorine

Oxotremorine caused contracture of rat phrenic nerve-diaphragm followed at high doses by blockade. Similar results were obtained on the sciatic nerve-tibialis anterior muscle preparation of the cat. The slowly developing spastic paralysis obtained with high doses was long lasting. Qualitatively similar results but of lower intensity were observed on chick biventer-cervicis nerve-muscle preparation. There was no effect on frog rectus abdominis preparation. On rat diaphragm contracture and paralysis were potentiated by halving the calcium chloride concentration and by physostigmine respectively. Depolarising effect was further proven by potentiation of reduction in the force and duration of tetanic response by physostigmine on rat diaphragm. An indirect mechanism involving release of acetylcholine is postulated.

Hydrolysis of suxamethonium by different types of plasma.

1. A method, based on the use of the isolated frog rectus abdominis preparation, is described for studying quantitatively the hydrolysis of suxamethonium at low concentrations.2. Rates of hydrolysis of butyrylcholine, 10 mM, benzoylcholine, 0.05 mM, and suxamethonium, 0.025 mM, by plasma from different species and human plasma with genetic variants of cholinesterase were measured.3. The rates of hydrolysis of suxamethonium by different types of plasma vary widely. Human plasma with usual cholinesterase and monkey plasma hydrolyse suxamethonium more speedily than do the plasma of cats, dogs and rats, and human plasma with either atypical or fluoride resistant cholinesterase. This is only to a small extent attributable to differences in enzyme concentration and not explained by the presence of an inhibitor.4. The K(m) values for butyrylcholine are very similar for different types of plasma but the K(I) values for suxamethonium in the system plasma-butyrylcholine-suxamethonium vary greatly.5. These results and observations on the inhibition by decamethonium of the hydrolysis of butyrylcholine are consistent with the interpretation that the rates of hydrolysis of suxamethonium, 0.025 mM, obtained with different types of plasma vary because they are a function of two variables, the affinity of the ester for cholinesterase and the stability of the monosuccinyl derivative of the cholinesterase. It seems that human plasma with atypical cholinesterase hydrolyses suxamethonium much slower than does human plasma with usual cholinesterase mainly or solely because of differences in affinity of the ester for the two enzymes. On the other hand, cat plasma appears to hydrolyse suxamethonium much slower than does human plasma with usual cholinesterase mainly because the monosuccinyl derivative of cholinesterase in cat plasma is much more stable than that in human plasma. The reverse might apply for monkey plasma.6. Inhibition by dibucaine or sodium fluoride of the hydrolysis of benzoylcholine is not a general guide to rates of hydrolysis of suxamethonium by different types of plasma.

Analogs of parasympathetic neuroeffectors—II: Comparative pharmacological studies of acetylcholine, its thio and seleno analogs, and their hydrolysis products

Acetylthiocholine and acetylselenocholine exert acetylcholine-like effects on the guinea pig ileum and frog rectus abdominis preparations. With the latter preparation, responses to acetylthiocholine and acetylselenocholine, in contrast to that to acetylcholine, are not enhanced by the addition of an anticholinesterase. This is attributable to the relatively high activity of the hydrolysis products, cholinethiol and cholineselenol; acetylthiocholine and acetylselenocholine undergo enzymatic hydrolysis at approximately the same rate as does acetylcholine. The hydrolysis products of acetylthiocholine and acetylselenocholine, which have effects on the guinea pig ileum comparable to those of the parent esters, are readily oxidized in air to the relatively inactive eholine disulfide and choline diselenide, respectively. These observations are helpful in explaining many of the apparently contradictory statements in the literature regarding the actions of acetylthiocholine.

THE INFLUENCE OF pH ON THE ACTIVITY OF NICOTINE AT THE NEUROMUSCULAR JUNCTION

The effects of pH on the activity of nicotine relative to that of nicotine monomethiodide have been studied on the frog rectus abdominis preparation. Results have been obtained which substantiate the view that it is the univalent nicotinium ion, rather than the un-ionized base, which acts at the neuromuscular junction.

THE INFLUENCE OF pH ON THE ACTIVITY OF NICOTINE AT THE NEUROMUSCULAR JUNCTION

The effects of pH on the activity of nicotine relative to that of nicotine monomethiodide have been studied on the frog rectus abdominis preparation. Results have been obtained which substantiate the view that it is the univalent nicotinium ion, rather than the un-ionized base, which acts at the neuromuscular junction.

The effect of ortho substitution on the pharmacology of benzolycholine.

Abstract The effects of mono- and di-ortho substitution of benzoylcholine on actions on the rat phrenic diaphragm and frog rectus abdominis preparations have been examined. Ortho substitution of benzoylcholine does not necessarily lead to a reduction in activity and may increase potency. It appears that mono-ortho-iodo substitution provides most stability combined with pharmacological activity.

Some properties of the sting of the New Zealand nettle,Urtica ferox

Extracts of hair fluid from a New Zealand stinging nettle (Urtica ferox) were tested on isolated rectus abdominis preparations of the frog,Hyla aurea. The muscle reacted in such a way as to indicate the presence in the hair fluid of acetylcholine (ca. 0⋅3 to 0⋅9μg per hair). Apart from the acetylcholine-like contraction, the muscle was subjected to a rapid irregular twitching in the presence of hair extract. The twitching could be reversibly suppressed or prevented by increasing the calcium content of the Ringer solution, or by adding mag­nesium, cobalt, strontium or nickel to the solution. The acetylcholine-like effect was not dis­turbed by such treatment. It is postulated that twitching results from a disturbance in the calcium metabolism of the muscle and a search for a 'calcium-sensitive’ factor indicates that it is neither phosphate, oxalate, formate, sulphate, fluoride, phytate, nor a chelating sub­stance similar toEDTA, but that it may be one of the guanidine group of compounds.