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PubMed1962

Effect of beta-diethylaminoethyl 3,3-diphenylpropylacetate on the action of suxamethonium and other neuromuscular blocking drugs.

On the frog rectus abdominis muscle and on sciatic nerve-tibialis anterior muscle preparations, beta-diethylaminoethyl 3,3-diphenylpropylacetate (SKF 525A) antagonized the actions of acetylcholine and potassium chloride as well as having an antiveratrine action. The blocking action at the skeletal neuromuscular junction of suxamethonium and its disulphonium analogue, decamethonium, tubocurarine and gallamine was enhanced by SKF 525A in the rabbit and in the isolated rat phrenic nerve-diaphragm preparation. The activity of suxamethonium and decamethonium in the cat was reduced. On the rat phrenic nerve-diaphragm preparation, pretreatment with SKF 525A abolished both the mutual antagonism between suxamethonium and tubocurarine and the antagonizing effect of tetraethylammonium against suxamethonium. Theantagonism between tetraethylammonium and tubocurarine was unimpaired.

Acetylcholine↗
PubMed1962

Activity of analogues of decamethonium on the chick biventer cervicis preparation.

The abilities of various decamethylenebisammonium compounds to cause contracture of the chick biventer cervicis preparation have been compared quantitatively with that of decamethonium. In the compounds tested the 1,10 substituents were similar and were ethyldimethylammonium, diethylmethylammonium, triethylammonium, hydroxyethyldimethylammonium and acetoxyethyldimethylammonium; decamethylenebisdimethylamine was also tested. The activity of the bisethyldimethylammonium compound is about one-third of that of decamethonium, that of the bisdiethylmethylammonium compound about one-twenty-eighth, but the other compounds are much less than one-hundredth as active. Even the bistriethylammonium compound, however, has some detectable activity although it is only a partial agonist. It is suggested that ability to depolarize the preparation depends upon the presence of methyl groups attached to the quaternary ammonium atom and also upon the presence of two such onium groups at the ends of the decamethylene chain. In these compounds the acetoxy group reduces ability to depolarize the preparation.

Animals↗
PubMed1985

Asymmetric block of a monovalent cation-selective channel of rabbit cardiac sarcoplasmic reticulum by succinyl choline.

We have investigated the effect of the skeletal muscle relaxant succinyl choline (SC) on the conduction of potassium ions through a monovalent cation-selective channel present in the cardiac muscle sarcoplasmic reticulum membrane (CSR). This channel has been studied under voltage-clamp conditions following the fusion of purified CSR membrane vesicles with preformed planar phospholipid bilayers. The channel assumes a fixed orientation in the bilayer and displays two conducting states (B. Tomlins, A.J. Williams & R.A.P. Montgomery, 1984, J. Membrane Biol. 80:191-199). SC blocks potassium conductance through the channel in a voltage-dependent manner. Block occurs from both sides of the channel, in both conducting states and is resolved as discrete "flickering" events. Although SC is capable of blocking potassium conductance from both sides of the membrane, block is asymmetric. The zero-voltage dissociation constant for block from the cis side of the membrane is approximately threefold lower than that from the trans side. Block from the cis side displays a linear dependence on SC concentration for both open states and is competitive with potassium ions at saturating potassium activities, consistent with a single-site blocking model. The degree of SC-induced block is also influenced by membrane surface charge. SC block differs from that previously described for bis quaternary ammonium (bis Qn) compounds such as decamethonium in that SC blocks preferentially from the cis side of the channel.

Animals↗
PubMed1963

The action of substances which block sympathetic postganglionic nervous transmission.

The substances which block sympathetic postganglionic transmission, xylocholine, bretylium and guanethidine, also block neuromuscular and sympathetic ganglionic transmission. To see if these last properties were related to the sympathetic blocking property, phenyltrimethylammonium, which blocks the neuromuscular junction (Riker, 1953), was used. It blocked the inhibition of the rabbit ileum produced by stimulating the periarterial nerves in the mesentery, though with higher concentrations the effect of stimulation was initially increased. The action was not modified by the presence of hyoscine. The blocking action was exerted on the response to stimulation of the highest frequency first, and on the response to stimulation of the lowest frequency last. This relation of block to stimulus frequency is similar to that at the neuromuscular junction when tubocurarine is used. Nine compounds have now been shown to block responses to sympathetic postganglionic stimulation, and seven of these are onium compounds. They are, however, mon-onium compounds, and not bis-onium compounds like hexamethonium and decamethonium, so that they can probably enter the postganglionic fibre, which bis-onium compounds (having a charged group at each end of the molecule) may not be able to do. Since these mon-onium compounds have some blocking action at neuromuscular junctions and at sympathetic ganglia, their block of postganglionic transmission may be essentially similar to that by hexamethonium at ganglia and to that by decamethonium at neuromuscular junctions. It is known that acetylcholine releases noradrenaline from sympathetic postganglionic terminations, and xylocholine and bretylium block this release in the vessels of the rabbit ear and in the rabbit isolated atria.

Acetylcholine↗
PubMed1988

Effects of some mono- and bisquaternary ammonium compounds on the reactivatability of soman-inhibited human acetylcholinesterase in vitro.

Acetylcholinesterase (AChE) inhibited by the organophosphate soman (1,2,2-trimethyl-propylmethylphosphonofluoridate) rapidly becomes resistant to reactivation by oximes due to dealkylation of the soman-enzyme complex. This reaction is called aging. The effect of the four mono- and bisquaternary ammonium compounds tetramethylammonium (TMA), hexamethonium, decamethonium and suxamethonium on the reactivatability of soman-inhibited, solubilized AChE from human erythrocytes was investigated in vitro. All compounds were reversible inhibitors of AChE; the respective dissociation constants and the type of inhibition exhibited considerable differences. The affinities to both the active and the allosteric site were considerably higher for suxamethonium (Kii 81.3 microM; Ki 15.9 microM) and decamethonium (Kii 15.4 microM; Ki 4.4 microM) than for TMA (Kii 1 mM; Ki 289.6 microM) and hexamethonium (Kii 4.5 mM; Ki 331.8 microM). The reactivation experiments were performed in a four-step procedure (soman-inhibition at 0 degree and pH 10, aging at 37 degrees and pH 7.3, reactivation by the oxime HI 6 at 37 degrees and pH 7.3 followed by AChE assay). After these four steps (total duration 55 min), AChE was inhibited by soman to 95-100%. HI 6 could reactivate about 20% of the inhibited enzyme. All effectors increased the AChE reactivatability by HI 6 when added before aging was started. The maximal increase in reactivatability was higher in the presence of 1.6 mM suxamethonium (+35.8%) and 150 microM decamethonium (+40%) than of 22 mM TMA (+22.5%) and 8.3 mM hexamethonium (+19.2%). If the effectors were added after 5 min of aging they increased the activity of soman-inhibited AChE, but to a considerably smaller extent than HI 6. A good correlation of the respective Kii values and the effective concentrations of these drugs was observed, indicating that an allosteric binding site of AChE might be involved in the protective effect of these drugs.

Acetylcholinesterase↗
PubMed1981

[Effects of mecamylamine and pempidine, secondary and tertiary amines, on the spinal reflex of cats (author's transl)].

The ganglionic blocking effects of the secondary and tertiary amines, mecamylamine and pempidine, on the spinal reflex of cats of both sexes were investigated. These blocking effects were then compared with findings in the quaternary ammonium compounds such as tetraethylammonium (TEA) and decamethonium (C10). Mecamylamine (5 mg/kg) and pempidine (1 mg/kg) inhibited spinal reflex potentials such as the monosynaptic reflex (MSR), the polysynaptic reflex (PSR) and the dorsal root reflex (DRR). Maximal inhibition occurred 40 min after intravenous administration these drugs. In the case of mecamylamine, the inhibited potentials recovered gradually after reaching the maximum inhibition. However, the inhibitory effect of pempidine was prolonged, and recovery of the potentials did not occur for 6 min or longer. Although 10 mg/kg of C10 and 0.025 mg/kg of nicotine transiently inhibited the MSR and PSR, these compounds had no effect on the DDR. TEA produced prolonged inhibition of the MSR and PSR, and slightly enhanced the DRR. These results demonstrated the differences in DRR responses to secondary and tertiary amines, and quaternary ammoniums.

Animals↗
PubMed1984

The characterization of a monovalent cation-selective channel of mammalian cardiac muscle sarcoplasmic reticulum.

Rabbit cardiac muscle sarcoplasmic reticulum (SR) was isolated and separated into ryanodine-sensitive and -insensitive fractions (L.R. Jones and S.E. Cala, J. Biol. Chem. 256:11809-11818, 1981). Vesicles of cardiac SR were incorporated into planar phospholipid bilayers by fusion and the channel activity of the membrane studied under voltage-clamp conditions (C. Miller, J. Membrane Biol. 40: 1-23, 1978). Both fractions contain a monovalent cation-selective three-state channel. In the presence of 75 mM K2SO4, the fully open state (beta) conductance of this channel is 157.2 +/- 30 pS and the sub-state (alpha) conductance is 100.7 +/- 21 pS. Both open states display the same selectivity sequence for monovalent cations, i.e. K+ greater than NH+4 greater than Rb+ greater than Na+ greater than Li+ and may be blocked by the skeletal muscle relaxants decamethonium and hexamethonium. Block occurs when the compounds are added to either side of the membrane. The properties of the cardiac SR cation channel are compared with those of the previously reported monovalent cation-selective channels of mammalian and amphibian skeletal muscle SR.

Animals↗
PubMed1978

Oxotremorine neuromuscular blockade: effects of calcium and neostigmine and interactions with D-tubocurarine and decamethonium.

The neuromuscular blocking effect of oxotremorine (OT) on the indirectly stimulated rat diaphragm preparation was compared with that of d-tubocurarine (TC) and decamethonium (C10). Approximate equieffective concentrations of these compounds were 20 micrometer for OT, 1.8 micrometer for TC, and 75 micrometer for C10. Increasing the Ca2+ concentration by 1 mM reduced the rate of onset of OT and C10 blockades whereas TC blockade was almost completely reversed. Neostigmine (NEO) antagonized TC blockade while OT and C10 blockades were enhanced. A facilitatory after-effect of NEO was suppressed in preparations previously exposed to OT but not in those previously exposed to TC or C10. C10 transitorily antagonized TC blockade but not OT blockade. OT did not antagonize TC blockade. A subreceptor effect may be involved in the action of OT and may explain its differences when compared to C10.

Animals↗
PubMedDate not supplied

[Study of skeletal muscle cholinoreceptors using alkylating agents].

The ability of decamethonium containing beta-clorethylamino groups to alkylate the nicotinic cholinoreceptors of the frog tonic muscles was studied. D-tubocurarine prevented the action of the alkylating decamethonium (AD). The latter equally inhibited the effects of carbacholine and tetramethylammonium. The degree of alkylation did not change with pH varying from 6 to 11. AD did not produce any parallel shifts, but inhibited at once the maximal response to carbacholine both of the frog intact muscle and of a single tonic fibre. It is suggested that decamethonium blocks the cholinoreceptors anionic sites, which are represented by the carboxylate, or phosphate anions. The frog tonic muscle probably fails to posses any spare receptors.

Alkylation↗