Blockade Of Neuromuscular Transmission Research Articles

The role of mast cells, C-fibers, and cholinergic transmission in the reduction of tracheal muscle and mronchi of sensitized animal

The article considers the role of stabilization of mast cell membranes, blockade of neuromuscular transmission and inactivation of C-fibers in the contractile activity of smooth muscles of the trachea and bronchi of sensitized rats. The studies were conducted on isolated preparations using electrical stimulation of postganglionic nerves (frequency - 30 stim/s, duration - 0.5 ms, amplitude - 20 V, duration of stimulation - 10 s). The study used cromolyn sodium, atropine, and capsaicin. As a result of the experiments, it was found that the leading role in the contraction of the muscles of the trachea and bronchi of a sensitized rat belongs to mast cells. However, the maximum effect of normalization of smooth muscle contraction can be achieved only in the case of a complex effect - blockade of neuromuscular transmission, stabilization of mast cell membranes, and inactivation of C-fibers.

Mechanism of MJ 1999-induced blockade of neuromuscular transmission.

Abstract MJ 1999 [4-(isopropylamino-1-hydroxyethyl)methanesulphonanilide hydrochloride] produced a dose-related blockade of indirectly evoked twitches of the rat diaphragm, without materially altering the effects of direct stimulation. The magnitude of blockade was comparable whether the indirect stimulation was at 1/s or 1/20 s. The blockade was less pronounced at 25° than at 34°. The blockade was antagonized by neostigmine, potassium chloride, succinyl-choline, tetraethylammonium, adrenaline, isoprenaline and, to some extent, by noradrenaline. Blockade by MJ 1999 was additive to that due to tubocurarine; large concentrations of yohimbine, tolazoline, phenoxybenzamine and dihydroergotamine quickly antagonized MJ 1999 blockade. Small concentrations of adrenaline, isoprenaline, tolazoline or yohimbine prevented MJ 1999 blockade. MJ 1999 had no effect on nerve conduction. It is proposed that MJ 1999 has a two-fold mode of action at the neuromuscular junction; a curare-like effect and an action on β-receptors.

Ultrastructural visualization of the transmembranous and cytomatrix-related part of nicotinic acetylcholine receptor of frog motor endplate by means of an immunochemical avidity of IgG for d-tubocurarine.

In the present study, a fine ultrastructural localization of nicotinic acetylcholine receptor (nAChR) was attempted, using d-tubocurarine (d-TC), a quaternary ammonium compound binding to nAChR. The localization was based on the binding avidity of immunoglobulin G (IgG) for acetylcholine (ACh) and other quaternary ammonium compounds, such as d-TC. d-TC was applied to the frog neuromuscular preparation and caused a blockade of neuromuscular transmission. Then, d-TC was rendered insoluble in situ by silicotungstic acid (STA), a precipitating agent of soluble proteins and quaternary ammonium compounds. After tissue fixation, a normal rabbit serum was applied to the fine precipitate of the insoluble salt of d-TC silicotungstate (quaternary ammonium radical of d-TC) to form the immunochemical complex d-TC- rabbit IgG at ACh binding sites. The IgG of the complex was revealed by means of the conventional immunoperoxidase procedure used for ultrastructural localization. Under the electron microscope, fine diaminobenzidine (DAB) precipitates appeared as regular rod-like structures oriented to cytoplasmic side of the horizontal part (crest) of the postsynaptic membrane (between the junctional folds) which is known to be endowed with nAChR. The rod-like precipitates were not observed in the postsynaptic junctional folds which are devoid of nAChR. The distance separating the rods each other was rather constant (12 - 15 nm), while the length of the rods was variable and exceeded the usual length of nAChR. The present work indicates that the rod-like structures, already observed in association with sarcoplasmic side of the postsynaptic membrane, did correspond to the intramembranous and intracytoplasmic part of nAChR and related proteins. These cytochemical results confirm that d-TC binds to ACh binding sites in the pore of nAChR, and raise the question of DAB staining of cytoskeletal proteins related to the nAChR complex.

Remote arteriolar dilations caused by methacholine: a role for CGRP sensory nerves?

Remote vasodilation caused by arteriolar microapplication of acetylcholine cannot be completely attributed to passive cell-cell communication of a hyperpolarizing signal. The present study was undertaken to ascertain whether a neural component may be involved in the remote response. In the cheek pouch of anesthetized hamsters, methacholine (100 microM) was applied to the arteriole by micropipette for 5 s, and the arteriolar responses were measured at the site of application and at remote locations: 500 and 1,000 microm upstream from the application site. Superfusion with the local anesthetic bupivacaine attenuated a local dilatory response and abolished the conducted dilation response to methacholine. Localized micropipette application of bupivacaine 300 microm from the methacholine application site also attenuated the remote dilation but did not inhibit the local dilation. Blockade of neuromuscular transmission with botulinum neurotoxin A (1 U, 3 days), micropipette application of calcitonin gene-related peptide (CGRP) receptor inhibitor CGRP-(8-37) (10 microM) 300 microm upstream from the methacholine application site, and denervation of the CGRP sensory nerve by 2 days of capsaicin treatment reduced the conducted dilation response to methacholine but did not affect the local dilatory response. Together, these data support involvement of a TTX-insensitive nerve, specifically the CGRP containing nerve, in vascular communication. Understanding the effect of regulation of a novel neural network system on the vascular network may lead to a new insight into regulation of blood flow and intraorgan blood distribution.

Neurotoxic and myotoxic actions of crotoxin-like and Crotalus durissus cascavella whole venom in the chick biventer cervicis preparation

Crotoxin from Crotalus durissus cascavella venom was purified by a combination of molecular exclusion chromatography (Superdex 75 column) and HPLC molecular exclusion (Protein Pack 300SW column). Neurotoxic and myotoxic effects from C. durissus cascavella whole venom and its main fraction, the crotoxin-like, were studied in the chick biventer cervicis (CBC) nerve–muscle preparation. Both venom and its crotoxin showed significant ( p<0.05) blockade of neuromuscular transmission at concentrations as low as 0.2–1, 5 and 25 μg/ml, but no significant effect has been shown with a concentration of 0.04 μg/ml ( n=5 each). The time required to produce 50% neuromuscular blockade with the venom and its crotoxin was 53.6±8.2 and 65.9±4.9 min (0.2 μg/ml), 29.7±1.9 and 34.3±1.9 min (1 μg/ml), 24.8±1.6 and 21.1±1.5 min (5 μg/ml), 20.9±3.7 and 20.1±1.4 min (25 μg/ml), respectively. The addition to the incubation bath of acetylcholine (55 and 110 μM) or KCl (20.1 mM), either before or after the venom or the crotoxin induced contracture in the presence of a total blockade, in all the concentrations used. Morphological analysis showed that the damage caused by C. durissus cascavella venom is stronger than that caused by crotoxin. The myonecrotic picture was more marked at higher venom and crotoxin doses (1, 5 or 25 μg/ml). Only at 25 μg/ml concentrations of the venom and crotoxin, marked muscle fiber changes were detected. We concluded that the crotoxin-like and the whole venom from C. durissus cascavella possess a preponderant and quite potent neurotoxic action in this preparation, and a myotoxic action which is observed only at higher doses.

Electro-acupuncture stimulation to muscle afferents in anesthetized rats modulates the blood flow to the knee joint through autonomic reflexes and nitric oxide

Recent reports have focused on the mechanisms of the action of electro-acupuncture stimulation (EAS) in the regulation of blood flow to different tissues. In the knee joint, blood flow is known to be modulated mainly by sympathetic postganglionic fibers, but recently the release or induction of nitric oxide (NO) synthesis in response to electrical stimulation has also been suggested. Therefore, a direct observation of the microcirculation is needed to further understand the mechanism by which blood flow is regulated by somatic afferent stimulation. In the present study, the effects of EAS to the vastus medialis muscle on systemic hemodynamics and the knee joint microcirculation were observed in vivo using a real-time confocal laser-scanning microscope system (CLMS). Electrical stimulation (5 mA, 0.5 ms, 5 Hz) was applied for 30 min using a pair of acupuncture needles introduced into the vastus medialis muscle. To clarify a plausible involvement of NO in the responses to EAS, the stimulus was applied either in the presence or absence of N ω-nitro-L-arginine methyl ester (L-NAME). Stimulation to either the muscle or the skin of the thigh after blockade of neuromuscular transmission was performed to determine the involvement of muscle contraction during EAS treatment. The changes in mean arterial pressure (MAP) and diameter of the arterioles supplying the knee joint were monitored continuously until 60 min poststimulus. Significant and persistent increases in arteriolar diameter by 26±6% and MAP by 17±2%, respectively, were observed after EAS to the muscle. Electro-acupuncture to the vastus medialis in the presence of L-NAME produced a strong decrease in diameter of the knee joint arterioles by −38±14% under the baseline with a simultaneous increase of 35±5% in MAP. EAS to the skin did not produce changes in arteriolar diameter while a slight increase in MAP by 12±6% over the baseline occurred after the stimulus. EAS to the muscle after neuromuscular blockade did not produce significant changes in diameter, while an increase in MAP by 24±8% was still observed, which facts suggest that the muscle contraction is required to produce vasodilatation. These responses suggest that a dynamic balance between the autonomic nervous system and the release of NO is the primary mechanism mediating the EAS effects on knee joint microcirculation.

Investigation of the head joints before, during and after an anesthesia with complete neuromuscular blockade

To determine wether a somatic dysfunction of head joints depends from segmental muscle strain, we investigated 89 patients before, during and after general anesthesia. We examined the disturbed joint motion as exclusive criterion for a somatic dysfunction, because through an anesthesia with endotracheal intubation including complete neuromuscular blockade segmental influences on the inspected joint were eleminated. For complete muscle relaxation as required for orotracheal intubation a non depolarizising muscle relaxant was used. Somatic dysfunctions were found most frequent for side-inclination and retroflexion in segment O/C1. Both before as well as during complete neuromuscular blockade could be found in the majority of examinations (89,1 %) similar restraints of joint motions. To 10,9 % were found, that somatic dysfunctions established before the muscle relaxant was applicated, were no more demonstrable under complete blockade of neuromuscular transmission. Different theoretical models are presented for the interpretation of our results. We assume, that the disturbance of one component of the metamer organized segment is the basic phanomenon of somatic dysfunction. This disturbance break through the spinal segmental inhibition and expand into the segment. Subsequently we discuss to replace the term "somatic dysfunction" through "segmental dysfunction" and to define it as increasing of nozizeptive afference in the segment over a determined period of time with breakthrough of the spinal segmental inhibition threshold. Based on the model of disturbed nerval – reflex functional circle we recommend for treatment at first chiropractic muscle relaxing techniques. The indication for manipulation is to be judged in case of rezidivation. The primary employment of manipulation appears promising, includes however in the area of head joints at faulty technology the danger of serious neurological complications.

Blockade of neuromuscular transmission by huwentoxin-I, purified from the venom of the Chinese bird spider Selenocosmia huwena

Huwentoxin-I (HWTX-I) is a neurotoxic peptide purified from the venom of the Chinese bird spider Selenocosmia huwena. The effects of HWTX-I on neuromuscular transmission of vertebrate skeletal muscle have been investigated by means of twitch tension and electrophysiological techniques. On isolated mouse phrenic nerve-hemidiaphragm preparations, HWTX-I blocked the twitch responses to indirect, but not to direct, muscle stimulation. The time needed for complete block of the neuromuscular transmission was dose dependent. The transmission could be mostly restored by prolonged repeated washing with Tyrode's solution. If the preparation was pretreated with d-tubocurarine and then immersed in a mixed solution of d-tubocurarine and HWTX-I, the washout time necessary to restore the neuromuscular transmission was significantly decreased. Intracellular recording at the end-plate region of frog sartorius muscle revealed that HWTX-I could synchronously reduce the amplitude of the acetylcholine potential induced by ionophoretic application of acetylcholine as well as the amplitude of the end-plate potential evoked by nerve stimulation. Both of these effects eventually disappeared; however, both could be restored by prolonged washing. Experiments on Xenopus embryonic myocytes indicated that HWTX-I reduced the open probability of acetylcholine-induced channel activity, and finally blocked the channel. All of these results demonstrated that HWTX-I was a peptide neurotoxin and the postsynaptic nicotinic acetylcholine receptor was its site of action.

Neuromuscular transmission and its pharmacological blockade. Part 1: Neuromuscular transmission and general aspects of its blockade.

Blockade of neuromuscular transmission is an important feature during anaesthesia and intensive care treatment of patients. The neuromuscular junction exists in a prejunctional part where acetylcholine is synthesized, stored and released in quanta via a complicated vesicular system. In this system a number of proteins is involved. Acetylcholine diffuses across the junctional cleft and binds to acetylcholinereceptors at the postjunctional part, and is thereafter metabolized by acetylcholinesterase in the junctional cleft. Binding of acetylcholine to its postjunctional receptor evokes muscle contraction. Normally a large margin of safety exists in the neuromuscular transmission. In various situations, apart from up-and-down regulation of acetylcholine receptors, adjustment of acetylcholine release can occur. Pharmacological interference can interrupt the neuromuscular transmission and causes muscle relaxation. For this reason both depolarizing and non-depolarizing muscle relaxants are clinically used. The characteristics of an ideal clinical muscle relaxant are defined. In the description of the pharmacology of the relaxants the importance of pharmacodynamic and pharmacokinetic parameters are defined. Stereoisomerism plays a role with the relaxants. Toxins and venoms also interfere with neuromuscular transmission, through both pre- and postjunctional mechanisms.

The effects of neonatal dorsal root section on the survival and dendritic development of lumbar motoneurons in the rat.

Peripheral nerve crush during the early neonatal period results in the death of a large proportion of affected motoneurons and abnormal dendritic development in those which survive. The present study reports the effects of neonatal dorsal root section on motoneurons supplying the extensor digitorum longus muscle of the rat. This lesion did not result in motoneuron death, but did disrupt subsequent dendritic development. In cells retrogradely labelled with cholera toxin subunit B conjugated to horseradish peroxidase, there was little change in adult dendritic morphology in the transverse plane, where abnormalities associated with loss of efferent contact and cell death have been found. However, there was a caudal expansion of the dendritic field, an effect seen following nerve crush but not after blockade of neuromuscular transmission alone. The results show that disruption of dorsal root sensory inputs alone can affect the dendritic development of motoneurons but does not cause their death. In conjunction with our earlier findings, it is clear that both afferent and efferent connections are required for normal dendritic development, and disruption of either has a characteristic effect on survival and dendritic morphology.

Muscle-Derived Neurotrophin-4 as an Activity-Dependent Trophic Signal for Adult Motor Neurons

The production of neurotrophin-4 (NT-4) in rat skeletal muscle was found to depend on muscle activity. The amounts of NT-4 messenger RNA present decreased after blockade of neuromuscular transmission with alpha-bungarotoxin and increased during postnatal development and after electrical stimulation in a dose-dependent manner. NT-4 immunoreactivity was detected in slow, type I muscle fibers. Intramuscular administration of NT-4 induced sprouting of intact adult motor nerves. Thus, muscle-derived NT-4 acted as an activity-dependent neurotrophic signal for growth and remodeling of adult motor neuron innervation. NT-4 may thus be partly responsible for the effects of exercise and electrical stimulation on neuromuscular performance.

Electrical Activity in the Neuromuscular Unit Can Influence the Molecular Development of Motor Neurons

During the first few weeks of postnatal life spinal motor neurons develop electrophysiological, morphological, and molecular features that are characteristic of adult motor neurons. To understand how the acquisition of the mature neuronal phenotype is regulated, we have examined the expression of the motor neuron cell surface proteoglycan recognized by monoclonal antibody Cat-301 in the hamster. Previously we found that Cat-301 immunoreactivity is not present on motor neurons at birth and that by the end of the second postnatal week all motor neurons are Cat-301-positive. Surgical and pharmacological lesion studies have shown that the onset of Cat-301 expression depends upon input from both large-diameter primary afferents and from supraspinal afferents. Once the Cat-301 proteoglycan is expressed on motor neurons, its continued expression is independent of these inputs. These studies suggested that motor neuron maturation depends upon the coordination of several afferent inputs during the first postnatal weeks of life. Our previous studies could not address whether segmental and descending afferents (i) provide a chemical signal (such as a trophic factor) or (ii) confer a pattern of neuronal activity upon motor neurons that then results in the expression of the Cat-301 proteoglycan. The present experiments examine the role of electrical activity in motor neuron maturation. In normal animals, all sciatic motor neurons are Cat-301-positive by Postnatal Day 19 (P19). Chronic application of the sodium channel blocker, tetrodotoxin (TTX), to the sciatic nerve in neonatal animals reduces the percentage of Cat-301-positive motor neurons found at P21 by one-third. This reduction is not due to a nonspecific inhibition of all protein synthesis, because the expression of two other motor neuron antigens proceeds normally in TTX-treated neonates. Blockade of neuromuscular transmission in neonates by Botulinus toxin A also reduces the percentage of Cat-301-positive motor neurons. Cat-301 expression is not tied simply to neuronal activity, because chronic application of TTX to the sciatic nerve, or Botulinus toxin A to muscles, in the adult does not reduce Cat-301 expression. These findings indicate that electrical activity generated within the neuromuscular unit in early postnatal life can influence the acquisition of mature molecular properties by motor neurons.

The downregulation of growth-associated proteins in motoneurons at the onset of synapse elimination is controlled by muscle activity and IGF1

Axonal growth during development and regeneration coincides with the expression of growth-associated proteins (GAPs), including GAP-43 and tubulin-alpha 1. Following contact with the target region and synaptogenesis, GAPs are downregulated. However, high levels of GAP-43 are expressed in some neurons in the adult CNS, indicating that its function may not be restricted to axonal growth. To define the type of signals that regulate GAP levels during development, we have determined whether GAP downregulation coincides with a defined phase of synapse development and whether it is controlled by the postsynaptic target. Levels of GAP-43 mRNA in spinal motoneurons and protein at the neuromuscular junction were analyzed in the developing neuromuscular system of chick and rat. In both species, GAP-43 mRNA declined rapidly at a time corresponding to the onset of synapse elimination, and nerve terminal GAP-43 immunoreactivity became undetectable with a delay of 2-3 d. In rat motoneurons, GAP-43 and tubulin-alpha 1 mRNA levels declined with a similar time course, indicating that at least two GAPs are downregulated at the same time. Blockade of neuromuscular transmission with either a pre- or a postsynaptically acting toxin prevented GAP downregulation, indicating that target activity affects GAP mRNA levels in motoneurons. Finally, counteracting the activity-dependent decline of muscle insulin-like growth factors during synapse elimination by local subcutaneous injections prevented motoneuron GAP downregulation, suggesting that these growth factors may be involved in the regulation of motoneuron GAPs by the muscle. These results demonstrate that motoneurons undergo target-sensitive changes in GAPs at the onset of synapse elimination. In addition, these results raise the possibility that termination of a presynaptic growth mode may be a prerequisite for synapse elimination.

Postganglionic nicotinic action of anatoxin-a on guinea pig ileum antagonized by thymopentin.

Anatoxin-a (ANTX) is a bicyclic amine exotoxin produced by the blue green algae Anabaena flos-aquae, and has been found to cause death to livestock and waterfowl via a blockade of neuromuscular transmission and subsequent respiratory paralysis (1, 2). ANTX has been shown to be a potent nicotinic cholinergic agonist in skeletal muscle (3), Torpedo electric organ (4) and mammalian central nervous system (5), and can also induce cardiovascular effects by activating nicotinic receptors in the adrenal medulla and sympathetic ganglia (6). We studied the effect of ANTX on guinea pig ileum.KeywordsBlue Green AlgaNicotinic ReceptorAdrenal MedullaSympathetic GanglionNeuromuscular TransmissionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

An extract of lionfish ( Pterois volitans) spine tissue contains acetylcholine and a toxin that affects neuromuscular transmission

A. S. Cohen and A. J. Olek. An extract of lionfish ( Pterois volitans) spine tissue contains acetylcholine and a toxin that affects neuromuscular transmission. Toxicon 27, 1367–1376, 1989.—A soluble toxic extract derived from spine tissue of the lionfish ( Pterois volitans) decreased heart rate and force of contraction in isolated clam and frog hearts. These actions were due to the presence of micromolar concentrations of acetylcholine in the extract. Toxicity was retained after hydrolysis of acetylcholine by exogenous acetylcholinesterase, but heart function was no longer affected. Toxin treated in this way induced muscle fibrillation in an isolated nerve-muscle preparation, followed by blockade of neuromuscular transmission. Bursts of transient depolarizations were recorded at the muscle endplate shortly after toxin addition that correlated in time with the duration of toxin-induced muscle fibrillation. These effects are thought to be due to the increased release and then depletion of acetylcholine from the nerve terminal.

In vitro blockade of neuromuscular transmission by monoclonal anti-acetylcholine receptor antibodies.

In vitro blockade of neuromuscular transmission by monoclonal anti-acetylcholine receptor antibodies.

Roles of the constituent chains of botulinum neurotoxin type A in the blockade of neuromuscular transmission in mice

Roles of the constituent chains of botulinum neurotoxin type A in the blockade of neuromuscular transmission in mice

Formula omitted][formula omitted] blockade of neuromuscular transmission by monoclonal anti-acetylcholine receptor antibodies

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Comparison of the action of types A and F botulinum toxin at the rat neuromuscular junction

Blockade of neuromuscular transmission was produced in the lower hind limb of the rat by local injection of either type A or type F botulinum toxin (BoTx). At 1, 3, 7, and 10 days after injection, the extensor digitorum longus (edl) nerve-muscle preparation was excised and analyzed for alterations in muscle mechanical properties or spontaneous and nerve stimulus-evoked quantal transmitter release. Muscles receiving type A toxin were paralyzed up to and including 7 days after injection. Muscles treated with type F toxin, although completely paralyzed at 1 and 3 days after injection, twitched in response to nerve stimulation by 7 days. Both toxins induced a marked decrease in the frequency of miniature end-plate potentials, but type A did so to a greater extent. Between 1 and 3 days after toxin injection nerve impulse-evoked transmitter release was reduced in both type A- and type F-treated muscles. Evoked release was temperature sensitive in type A-treated muscles but not in those treated with type F. 3,4-Diaminopyridine (3,4-DAP), a compound which increases nerve-evoked transmitter release by increasing Ca 2+ influx, was more effective in reversing the paralysis in type A than in type F-treated muscles, 3,4-DAP induced asynchronous end-plate potentials in response to nerve stimulation in type F-paralyzed muscles, but not in muscles treated with type A. Amidination of the amino groups (presumably lysine) on the toxin by treatment with ethylacetimidate increased the potency and efficacy of only type F BoTx. The results show that type F BoTx differs from type A, mainly by its lower potency, efficacy, shorter duration of action, and by being less effectively antagonized by 3,4-DAP.

Effect of chronic presynaptic neuromuscular transmission block on properties of frog muscle fiber membranes

It has been discovered in experiments on frogs that muscle denervation removes the membrane rest potential, increases the input resistance and time constant of the membrane, expands the zone of muscular fiber sensitivity to acetylcholine. Long-term disturbance by tetrodotoxin of the excitation conduction in the motor nerve or presynaptic blockade of neuromuscular transmission by hemicholinium-3 do not change the membrane rest potential and time constant of the membrane or the size of the zone of muscular fiber sensitivity to acetylcholine but increase the input resistance of the muscle membrane. It is inferred that in the frog, presynaptic blockade of the excitation conduction from the nerve to the muscle is not equivalent to its denervation.