Rectus Abdominis Muscle Preparation Research Articles

<em>In Vitro</em> Anticholinergic and Antihistaminic Activities of <em>Acorus Calamus</em> Linn. Leaves Extracts

The present investigation was aimed at determining the effects of hexane, acetone, methanol and aqueous extracts of Acorus calamus leaves (ACHE, ACAE, ACME and ACAQE) on cholinergic and histaminic system using isolated frog rectus abdominis muscle and guinea pig ileum. A dose dependent potentiation of Ach response (anticholinesterase like effect) was found with ACAE and ACME at 0.25, 0.5, 0.75 and 1 mg/ml, but at higher dose of ACAE, ACME, ACAQE and ACHE (5, 20 mg/ml) inhibit the Ach response (antinicotinic effect). These results revealed biphasic effect of Acorus calamus leaves extracts on acetylcholine induced contractile response in isolated frog rectus abdominis muscle preparation (i.e. potentiation effect at lower dose and inhibitory effect at higher dose). Studies on isolated guinea pig ileum demonstrated antihistaminic effect in a dose dependent manner (100-1000 µg/ml) with ACAE, ACME and ACAQE. In addition, the dose dependent inhibition of Ach response (antimuscarinic effect) was observed with ACAE and ACME. In conclusion, Acorus calamus leaves extracts exerts antinicotinic, anticholinesterase like activities in isolated frog rectus abdominis muscle and antihistaminic, antimuscarinic effect in guinea pig ileum. It has been suggested that these observed activities can be further studied for therapeutic potential of Acorus calamus leaves in the treatment of cognitive disorders and asthma.

Design, synthesis and evaluation of novel 16-imidazolyl substituted steroidal derivatives possessing potent diversified pharmacological properties

As a part of our investigations into the structural–activity relationship studies of a novel class of medicinally active 16-substituted steroids, several new 16-imidazolyl substituted steroidal derivatives have been synthesized and pharmacologically evaluated in the current study. The new steroidal analogues 5, 6, 8, 9, 11 and 12 exhibited moderate cytotoxic effects in sixty cancer cell lines derived from nine cancers types. The imidazolyl substituted steroidal derivatives 6 (DPJ-RG-1241) and 7 (RB-401) were obtained as the powerful inhibitors of aromatase with IC50=0.18μM and IC50=0.168μM, respectively, approximately 1.2 and 1.4times more potent in comparison to standard drug exemestane. The bis-quaternary steroids 13 and 14 displayed potent skeletal muscle relaxant properties. An affinity constant of 0.007μM was observed for compound 14 on frog rectus abdominis muscle preparation and 13 displayed a very high anticholinesterase activity Ki=25nM, approximately 115-fold higher in comparison to standard drug galanthamine (Ki=2.9μM).

Lactic acid restores skeletal muscle force in an in vitro fatigue model: are voltage-gated chloride channels involved?

High interstitial K(+) concentration ([K(+)]) has been reported to impede normal propagation of electrical impulses along the muscle cell membrane (sarcolemma) and then also into the transverse tubule system; this is one considered underlying mechanism associated with the development of muscle fatigue. Interestingly, the extracellular buildup of lactic acid, once considered an additional cause for muscle fatigue, was recently shown to have force-restoring effects in such conditions. Specifically, it was proposed that elevated lactic acid (and intracellular acidosis) may lead to inhibition of voltage-gated chloride channels, thereby reestablishing better excitability of the muscle cell sarcolemma. In the present study, using an in vitro muscle contractile experimental setup to study functionally viable rectus abdominis muscle preparations obtained from normal swine, we examined the effects of 20 mM lactic acid and 512 μM 9-anthracenecarboxylic acid (9-AC; a voltage-gated chloride channel blocker) on the force recovery of K(+)-depressed (10 mM K(+)) twitch forces. We observed a similar muscle contractile restoration after both treatments. Interestingly, at elevated [K(+)], myotonia (i.e., hyperexcitability or afterdepolarizations), usually present in skeletal muscle with inherent or induced chloride channel dysfunctions, was not observed in the presence of either lactic acid or 9-AC. In part, these data confirm previous studies showing a force-restoring effect of lactic acid in high-[K(+)] conditions. In addition, we observed similar restorative effects of lactic acid and 9-AC, implicating a beneficial mechanism via voltage-gated chloride channel modulation.

Antinicotinic activity of some 2-aminotetralin derivatives. A structure-activity relationship study.

The antagonistic potencies of some methoxy-2-aminotetralin derivatives on nicotinic type acetylcholine receptors were compared in rat anococcygeus muscle and frog rectus abdominis muscle preparations. Stimulation of intrinsic non-adrenergic non-cholinergic (NANC) nerves with nicotine (100 mumol/l) produced a 65.7 +/- 3.2% relaxation in phenylephrine (1 mumol/l) precontracted (2.53 +/- 0.20 g) preparations (n = 17). 2-Aminotetralin derivatives inhibited the nicotine-induced relaxations in rat anococcygeus muscle in a concentration-dependent manner with the following order of potency: BDI-60 > BDI-85 > BDI-51. Preincubation of frog rectus abdominis muscles with the test compounds caused noncompetitive antagonism as reflected by significant reductions in the maximum contractions obtained with nicotine. The order of potency according to their pD2' values was BDI-60 > BDI-85 > BDI-51. All three compounds possess antagonistic action with the same order of potency on both neuronal and muscular type nicotinic acetylcholine receptors. It has been concluded that doubling the n-propyl residue on the 2-amino moiety causes an increase in the antagonistic potency on nicotonic type acetylcholine receptors, while shifting of the 8-methoxy residue to the fifth position reduces it.

Effect of Ceftriaxone on Isolated Smooth, Cardiac Muscles and Neuromuscular Junctions

The pharmacodynamic effect of ceftriaxone on smooth muscles was investigated in isolated organs. Maximum stimulation of isolated guinea pig\\\'s ileum, rabbit\\\'s duodenum and rat\\\'s fundic strip was achieved by addition of 1024 µg of ceftriaxone/ml bath. While in isolated rat\\\'s colon, it was achieved by 512 µg of ceftriaxone/ml bath. The effect of graded increased concentrations of ceftriaxone on isolated rat\\\'s uterine muscles was examined during various stages of sex cycle. Ceftriaxone in the tested concentrations produced a dose-dependant negative inotropic effect on isolated rabbit\\\'s heart and guinea pig\\\'s auricles. Ceftriaxone in all tested concentrations did not induce any effects on the resting tonus of isolated guinea pig\\\'s tracheal chain and rabbit\\\'s aortic strip. Neuromuscular blockade effect was investigated on isolated frog\\\'s gastrocnemius muscle and frog\\\'s rectus abdominis muscle preparation. It was concluded that, ceftriaxone directly stimulates the smooth muscles of gastrointestinal tract and depresses those of uterus as well as cardiac muscles. These findings indicated that ceftriaxone had scarcely any pharmacological properties which might be leading to severe adverse reactions in clinical use.

In Vitro Effects of Propofol and Volatile Agents on Pharmacologically Induced Chloride Channel Myotonia

Anesthetic choice for patients with chloride channel myotonia remains under debate. The authors have, therefore, investigated the in vitro effects of various anesthetic agents on pharmacologically induced chloride channel myotonia. Functionally viable (> 10 mN force generation) rectus abdominis muscle preparations obtained from normal swine were investigated using in vitro muscle contracture test baths. During continuous 0.1-Hz supramaximal electrical stimulation, the chloride channel blocker 9-anthracenecarboxylic acid (64 microM) was added before the addition of propofol or one of three volatile anesthetics. The concentration of propofol in either Intralipid (n = 11) or dimethyl sulfoxide (n = 10) was doubled every 10 min (from 4-512 microM). The concentration of halothane (n = 8), isoflurane (n = 8), and sevoflurane (n = 8) was doubled from 0.25 vol% up to the maximum dose according to calibrated vaporizers. Control muscle bundles were either untreated (n = 30) or exposed to 9-anthracenecarboxylic acid (n = 19). The myotonic reactions induced by 9-anthracenecarboxylic acid were reversed by high-dose (> 64 microM) propofol (P < 0.01). Halothane, isoflurane, or sevoflurane each enhanced the myotonic reactions at 5.4 (P < 0.001), 0.21 (P < 0.01), and 0.5 minimum alveolar concentrations (P < 0.05), respectively. The authors' in vitro data imply that propofol administration for general anesthesia may be better suited for patients with chloride channel myotonia versus volatile anesthetics. In isolated swine skeletal muscle bundles, propofol elicited a reversal of 9-anthracenecarboxylic acid-induced chloride channel myotonia, whereas volatile anesthetics further increased the associated myotonic reactions.

Preliminary studies with a neurotoxin obtained from Bungarus caeruleus venom

The neurotoxin purified from the venom of Bungarus caeruleus causes a neuromuscular blockade on acetylcholine-induced muscle twitch response in isolated frog rectus abdominis muscle preparation. Neuromuscular blockade produced by d-tubocurarine on acetylcholine-induced muscle twitch response in an isolated frog rectus abdominis muscle preparation was reversed to normal muscle twitch response in presence of neostigmine. Whereas the purified neurotoxin produced an irreversible neuromuscular blockade in presence of the same strength of neostigmine. As it is already known, botulinum toxin, which also brings about neuromuscular blockade, is effectively used as a drug in the treatment of painful movement disorders. Since the purified toxin also causes paralysis of the muscle, we propose its possible efficacy in the treatment of neuromuscular disorders.

PHARMACOLOGY OF AFRICAN MEDICINAL PLANTS: NEURO MUSULAR AND CARDIOVASCULAR PROPERTIES OF SEGURIDACA LONGIPENDUNCULATA

The neuromuscular and cardiovascular properties of 60% methanol extract of the root bark of Securidaca longipedunculata (Fresen.) have been examined in vitro and in vivo, using laboratory anaimal models. The extract (MESL) at 50-250 mg/ml inhibited or abolished contractions of the frog rectus abdominis muscle preparations induced by acetycholine (Ach), arbachol, or nicotine (0.1-10mg/ml) in a dose dependent manner. The same concentrations of the extract always depressed or a bolished indirect or direct electrical stimulation-induced maximal twitches of the chick biventer or rat hemidiaphragm muscle preparations in a concentration-related manner. MESL provoked neuromuscular blockade was only partially reversed by physostigmine (PHY, 5-10mg/ml), which rapidly and completely reversed the neuromuscular blockade, instituted by d-tubocurarine (dTC, 1-10mg/ml). Nevertheless, exogenous administration of calcium (Ca 2+ 2+ Key Words: Securidaca longipedunculata; Polygalaceae; Root Bark; Methanolic Extract; Neuromuscular and Cardiovascular Properties Nig. J. Nat Prod. And Med. Vol.4 2000:30-36

4-chloro-m-cresol triggers malignant hyperthermia in susceptible swine at doses greatly exceeding those found in drug preparations.

Chlorocresols are used as preservatives in numerous commercial drugs that have been shown to induce myoplasmic Ca2+ release; the most potent isoform is 4-chloro-m-cresol. The aims of this study were to (1) examine the in vivo effects of 4-chloro-m-cresol on swine susceptible to malignant hyperthermia and (2) contrast in vivo versus in vitro dose-response curves. Susceptible swine (weight: 38.5 kg+/-3.55 kg) were anesthetized and monitored for variations in physiological responses, including end-tidal CO2, heart rate, blood pressure, blood chemistry, and temperatures. In the first animals studied, 4-chloro-m-cresol, at equivalent cumulative doses of 0.14, 0.28, 0.57, 1.14, 2.27, 4.54, and 9.08 mg/kg (n = 3; 12.5, 25, 50, 100, 200, 400, and 800 micromol) were administered, and in a second group, larger doses were used: 1.14, 3.41, 7.95, 17.04 (n = 4), and/or 35.22 (n = 1) mg/kg (100, 300, 700, 1,500, and/or 3,100 micromol). For comparison, in vitro rectus abdominis muscle preparations obtained from normal and susceptible swine were exposed to 4-chloro-m-cresol, at cumulative concentrations of 6.25, 12.5, 25, 50, 100, 200, 400, 800, and 1,600 micromol; standard caffeine and halothane contracture testing was also performed. Episodes of malignant hyperthermia were not triggered in response to administration of low doses of 4-chloro-m-cresol, but transient cardiovascular reactions (e.g., tachycardia, arrhythmias, and hypotension) were observed. Subsequently, episodes in these animals were triggered when halothane (0.87; 1 MAC) and succinylcholine (2 mg/kg) were given. Animals administered the higher doses of 4-chloro-m-cresol all had fulminant episodes of malignant hyperthermia that were fatal, when equivalent cumulative concentrations were greater than 1,500 micromol. The levels of 4-chloro-m-cresol in the plasma rapidly decreased: e.g., 5 min postadministration of the 1,500-micromol dose, the mean plasma level was only 52+/-18 micromol (n = 4). Hemolysis was detected following 4-chloro-m-cresol administration at concentrations > 200 micromol. In vitro, muscle from susceptible animals elicited contractures > 200 mg at 50-micromol bath concentrations of 4-chloro-m-cresol (n = 29), whereas normal muscle did not elicit such contractures until bath concentrations were > 800 micromol (n = 10). 4-chloro-m-cresol is a trigger of malignant hyperthermia in susceptible swine, but only when serum concentrations are far above those likely to be encountered in humans. A relatively low concentration of 4-chloro-m-cresol, 50 micromol, is sufficient to activate sarcoplasmic [Ca+2] release in vitro (e.g., contractures); this same bolus dose administered in vivo (0.57 mg/kg) has minimal effects due to the rapid decrease in its plasma levels.

Skeletal muscle relaxant properties of the aqueous extract of portulaca oleracea

The skeletal muscle relaxant properties of an aqueous extract of Portulaca oleracea were examined on the twitch and tetanus tension evoked by electrical stimulation using the rat phrenic nerve-hemidiaphragm and frog sciatic nerve-sartorius muscle preparations and on contractures induced by nicotinic agonists using the rat rectus abdominis muscle preparation. The extract (5—50 × 10 −4 g ml ) produced a dose-dependent initial enhancement, followed by a longer lasting depression of twitch tension as induced by indirect electrical stimulation (NS) as well as direct stimulation (MS) of the diaphragm and sartorius muscle preparations. The augmentation of twitch amplitude (MS) produced by the extract was not significantly antagonised or potentiated by d-tubocurarine (5—50 × 10 −8 M) or physostigmine (5—50 × 10 −8 M) at concentrations which blocked or potentiated NS-induced twitch contractions. Furthermore, tetrodotoxin (5 × 10 −7 g ml ) alone or in combination with d-tubocurarine did not significantly attenuate extract-induced augmentation of twitch contractions to MS. In addition, the depression of twitch tension due to NS was not antagonised by physostigmine but was reversed and/or abolished by Ca 2+ (2—5 × 10 −3 M or potassium thiocyanate (1× 10 −3 M). Contractures induced by K + (80 mM) or by tetanic stimulation (20—60 Hz) were significantly reduced by the extract whereas, contracture induced by caffeine (2.5—6.0 mM) was not affected. Ca 2+-free Tyrode's solution and EDTA (1.25 × 10 −3 g ml ) potentiated extract-induced depression of twitch tension to MS. On the rectus abdominis, contractures induced by nicotinic agonists (acetylcholine, 3—500 × 10 −7 M; carbachol, 5—500 × 10 −7 M and nicotine, 5—500 × 10 −8 M were significantly attenuated and/or abolished by the extract (5—10 × 10 −3 g ml ). These observations indicate that the aqueous extract possesses unique skeletal muscle relaxant properties which do not appear to involve interference with cholinoceptor mechanism(s). It appears that the mechanism of action of the extract may involve interference with Ca 2+ mobilization in skeletal muscle.

Effects on muscle of a toxin from indian cobra ( Naja naja naja) venom

—The mode of action of a purified toxin from Naja naja naja (Indian cobra) venom was investigated in frog rectus abdominis muscle, chick biventer cervicis muscle, cat tibialis anterior muscle (close-arterial) and in both innervated and denervated rat diaphragm muscle preparations. The toxin inhibited the acetyl-choline responses of rectus abdominis muscle. The inhibition was antagonized by neostigmine and increasing concentrations of acetylcholine, suggesting a competitive binding of the toxin to cholinergic receptors. The toxin, even at high doses, did not produce depolarizing contractures in chronically denervated diaphragm, biventer cervicis muscle and rectus abdominis muscle preparations. In both cat tibialis anterior and denervated diaphragm muscles, the toxin abolished the acetylcholine sensitivity of the muscles at a faster rate than its effects on muscle contraction, suggesting a preferred action on the motor end-plate. A well-maintained tetanic contraction and very poor post-tetanic potentiation was observed in all preparations treated with toxin, indicating an atypical Wedensky inhibition. Anti-curare agents, such as K + and Ca 2+, were ineffective in antagonizing the curare-like neuromuscular block in phrenic nerve-diaphragm preparations. A frequency-independent neuromuscular block observed in these nerve-muscle preparations was suggestive of the absence of a possible presynaptic effect. These results demonstrate that although the neurotoxin in some cases can imitate d-tubocurarine, its neuromuscular blocking activity is different from that of curare in many respects.

Inhibition of nicotinic responses at neuromuscular junctions by 3,3-dimethyl-1-butanol carbamate (DBC)

The action of 3,3-dimethyl-1-butanol carbamate (DBC), a synthetic carbachol analogue in which the quaternary nitrogen atom has been replaced by a carbon atom, has been studied in relation to its effects on nicotinic responses. In the thick biventer cervicis nerve-muscle preparation and frog rectus abdominis muscle preparation, DBC inhibited the responses elicited by nicotine and dimethylphenylpiperazinium at concentrations that did not affect responses induced by acetylcholine. DBC ( −4–10 −3M) depressed markedly the uptake of 3H-nicotine (2 × 10 −3M) into the frog rectus abdominis muscle preparation. In the innervated chick biventer cervicis nerve-muscle preparation, DBC (10 −3M) also decreased the uptake of 3H-nicotine (2 × 10 −3M), but in denervated preparations, DBC had no effect. It is concluded that the peripheral antinicotinic actions of DBC require an intact nerve-muscle junction and are due to a blockade in the uptake of nicotine into nerve fibers.

Actions of the selective inhibitor of cholinesterase tetramonoisopropyl pyrophosphortetramide on the rat phrenic nerve-diaphragm preparation.

1. Tetramonoisopropyl pyrophosphortetramide (iso-OMPA) added for 15 min to the rat isolated phrenic nerve-diaphragm in a concentration of 30 muM, produced a complete selective and stable inhibition of cholinesterase. A concentration of 3 muM produced near complete inhibition of cholinesterase, and a concentration of 300 muM also inhibited acetylcholinesterase marginally.2. Inhibition of cholinesterase was associated with a sustained increase in the neuromuscular blocking action of exogenous butyrylcholine but not of exogenous acetylcholine. Iso-OMPA, 300 muM, in addition caused transient increases in the sensitivity of the rat diaphragm to exogenous acetylcholine and butyrylcholine. In the same concentration, it had a curare-like action on the frog rectus abdominis muscle preparation.3. Iso-OMPA, 30 muM, caused reversible increases in the amplitude of the twitch response and tetanic responses, which were of a similar magnitude in the indirectly stimulated preparation and the directly stimulated curarized preparation. Caffeine had a similar effect on the twitch response and its effectiveness was increased by iso-OMPA, and vice-versa. Amongst anticholinesterases, octamethyl pyrophosphortetramide and tetraethylpyrophosphate also enhanced the amplitude of the tetanic response, but paraoxon, dyflos, and mipafox did not.4. It is concluded that iso-OMPA, in concentrations (3 and 30 muM) which in 15 min give near maximal or maximal selective inhibition of cholinesterase, has no effect on the transmission of nerve impulses at the neuromuscular junction, but enhances reversibly the amplitude of the contractile response to stimulation by a direct action upon the muscle fibre, which involves a mechanism related to but not identical with that by which caffeine potentiates twitch tension. In higher concentrations, iso-OMPA has a curare-like action at the neuromuscular junction.

Metabolism and significance of acetylcholine in the brain of the adult housefly, Musca domestica L.

Methods are described for the determination of [ 14C] acetylcholine formed in the head tissues of the adult housefly in vivo following [ 14C] acetate injection. Acetylcholine estimated radiometrically and that assayed pharmacologically were in good agreement. This confirms that this ester largely, if not entirely, accounts for the pharmacological activity of head extracts as assayed with the frog rectus abdominis muscle preparation. The data indicated that the acetylcholine content of the brain is due to a steady state of synthesis and hydrolysis with a minimum turnover rate of 6·1 × 10 −5 μmoles acetylcholine/min/head. Turnover was apparently reduced in insects poisoned with acetylcholinesterase inhibitors. These and other observations are interpreted as showing that the ACh system of the brain is highly compartmentalized, synthesis from choline and intracellular acetate being controlled by the availability of choline arising from acetylcholinesterase action. No correlation was found between acetylcholine turnover in vivo and the incidence of light on the compound eye. Turnover was apparently unaffected by surgical elimination of possible nerve activity originating in the thoracic ganglion. It was, apparently, reduced during cyclopropane anaesthesia. Current problems of insect neurophysiology are critically discussed.

RELATIVE ACTIONS OF QUATERNARY METHYL DERIVATIVES OF TYRAMINE, DOPAMINE AND NORADRENALINE.

Tyramine methiodide and dopamine methobromide have greater pressor effect (three- to five-times) in the spinal cat than the parent amines. Noradrenaline methochloride has little pressor effect. Dopamine methobromide is about four times as potent as nicotine; tyramine methiodide is about equiactive to nicotine; and noradrenaline methochloride has only one-tenth the potency of nicotine. Their pressor effects are usually abolished by hexamethonium but in some experiments the effect of noradrenaline methochloride persisted and was then abolished by tolazoline. Injected intravenously into the cat anaesthetized with chloralose, each of the three quaternary derivatives contracts the nictitating membrane; dopamine methobromide is again the most active, having more than six times the potency of nicotine. When the contractions of the nictitating membrane are induced by continuous stimulation of the preganglionic fibres of the cervical sympathetic nerve, intravenous injection of the quaternary derivatives of tyramine and dopamine has a biphasic effect; there is a block on which a contraction of the membrane appears to be superimposed. Noradrenaline methochloride produces only a further contraction of the membrane. On the isolated rectus abdominis muscle preparation of the frog, dopamine methobromide is the most active in contracting the muscle, being about twelve times as active as nicotine; noradrenaline methochloride is weakest, having only one-hundredth the activity of nicotine. These effects are antagonized by hexamethonium. On the isolated phrenic nerve-diaphragm preparation of the rat, the quaternary derivatives of tyramine and dopamine each have neuromuscular blocking properties, 0.7- and 3-times respectively that of nicotine. Noradrenaline methochloride has no effect. In the sciatic nerve-tibialis preparation of the cat, the quaternary derivatives of tyramine and dopamine are approximately equipotent in producing neuromuscular paralysis, having about three times the activity of nicotine and one-fifth that of suxamethonium. These effects are not antagonized either by neostigmine or by edrophonium. Noradrenaline methochloride has no neuromuscular blocking effect. The nicotine-like properties of these quaternized sympathomimetic amines are discussed. It is of interest that the presence of an hydroxyl group attached to the beta-carbon atom of the side-chain greatly reduces nicotine-like activity. By comparison, choline had about one forty-fifth the pressor activity of ethyltrimethylammonium.

Effect of inorganic complex ions on transmission at a neuromuscular junction.

SOME aspects of the chemical and biological activity of the inorganic complex ions have been previously reported by Beccari1 and by Dwyer and co-workers2–4. These workers have indicated that the complex cations show extremely high chemical stability, and most probably pass through the body unchanged. They also exhibit marked biological activity4, and when injected intraperitoneally into mice2 cause paralysis and death by respiratory failure suggestive of curariform activity. We have investigated their pharmacological mode of action on the rat diaphragm–phrenic nerve and toad (Bufo marinus) rectus abdominis muscle preparations. Investigations have also been carried out, in collaboration with Dr. Rosamond M. Eccles, of the Department of Physiology, Australian National University, using the toad sartorius nerve–muscle preparation and the isolated superior cervical ganglion of the rabbit.