Frog Rectus Research Articles

Pharmacological effects of Synclisia scabrida alkaloid B on some isolated muscle preparations

Alkaloid B reversibly blocked the responses of rat diaphragm to electrically induced stimulations via the phrenic nerve. The alkaloid had no effect on the responses of the diaphragm elicited by direct electrical stimulation. The responses of frog rectus abdominis muscle to acetylcholine were inhibited by alkaloid B. Alkaloid B reversibly antagonised the responses of rabbit duodenum to exogenously applied acetylcholine. The contractile effect of oxytocin on rat uterus was specifically inhibited by alkaloid B. The effects of alkaloid B on isolated muscle preparations were concentration-dependent. However, the effect of dopamine and noradrenaline on rat vas deferens was not altered by alkaloid B.

The effect of a benzodiazepine, flurazepam, on the response of in vitro skeletal muscle preparations to muscle relaxants: are purines or their receptors involved?

Changing trends in the use of anxiolytic agents and recent reassessment of their neuropharmacological activity has prompted this evaluation of the peripheral neuromuscular activity of the benzodiazepine, flurazepam. In previous reports we have documented peripheral neuromuscular activity of chlordiazepoxide and diazepam on the rat phrenic nerve diaphragm preparation. The water soluble benzodiazepine, flurazepam, has been studied on the rat phrenic nerve diaphragm and frog rectus abdominis in vitro. On the former preparation flurazepam enhanced and then blocked the response to indirect electrical stimulation (0.2 Hz) and readily blocked posttetanic potentiation and prevented the preparation from sustaining a tetanic contracture (30 Hz). On the later preparation, flurazepam blocked in a noncompetitive manner the response of the frog muscle to applied cholinergic agonists. Studies on the rat preparation with the neuromuscular blocking drug succinylcholine have shown an unexpected protection against blockade in preparations pretreated with low concentrations of flurazepam. This was not observed when flurazepam was given prior to d-tubocurarine. The application of adenosine to rat diaphragms during steady-state partial blockade caused by flurazepam or d-tubocurarine showed an inhibiting action of adenosine which was reversed by theophylline. Pretreatment of rat preparations with dipyridamole significantly enhanced the blocking action of standard concentrations of succinylcholine. These results, along with those in the literature, encourage a reassessment of the action of purines and benzodiazepines on skeletal muscle and encourage a consideration of a possible involvement of purinergic neuromodulation of transmission which is unmasked when the safety factor for transmission is altered by muscle relaxants. The possible clinical significance of protection against succinylcholine by benzodiazepines is noted.

Studies on chemotherapy of parasitic helminths (IV). Effects of alkaloids from Sophora flavescens on the motility of parasitic helminths and isolated host tissues (author's transl)

Effects of N-methylcytisine (N-MC) and matrine (Mat), alkaloids from Sophora flavescens on the motility of parasitic helminths and isolated frog rectus and mouse ileum were studied. 1) The motility of Angiostrongylus cantonensis was affected spastically by N-MC (1.2 X 10(-6) approximately 1.2 X 10(-4) M), but paralytically by Mat (10(-5) approximately 10(-4) M). 2) The motility of Dipylidium caninum and Fasciola hepatica was affected paralytically by N-MC (1.2 X 10(-4) approximately 1.2 X 10(-3) M), but spastically by Mat (10(-4) approximately 10(-3) M). 3) Treatment with N-MC (10(-3) M) and Mat (8 X 10(-4) M) had little effect on the motility of Schistosoma japonicum. 4) Both N-MC (1.2 X 10(-5) approximately 2.4 X 10(-5) M) and Mat (10(-4) M) stimulated the twitch response induced by guanidine (2.5 X 10(-5) M) in the frog isolated rectus preparation. 5) The motility of the mouse isolated ileum preparation was affected paralytically by N-MC (1.2 X 10(-5) approximately 1.2 X 10(-4) M), but spastically by Mat (10(-4) approximately 10(-3) M). Thus, N-MC and Mat acted antagonistically on all the preparations with the exception of the frog rectus preparation. From the results on interactions between these alkaloids and known neuropharmacological agents, it is suggested that the effects of both alkaloids are elicited through a neuropharmacological mechanism in parasitic helminths and host tissues.

Studies on chemotherapy of parasitic helminths (III). Effects of tuberostemonine from Stemona japonica on the motility of parasitic helminths and isolated host tissues (author's transl)

Effects of tuberostemonine (TS), an alkaloid from Stemona japonica, on the motility of parasitic helminths and isolated frog rectus and mouse ileum were studied. 1) TS (6.7 X 10(-6) approximately 2 X 10(-5) M) paralyzed the motility of Angiostrongylus cantonensis. 2) TS (6.7 X 10(-5) M) showed contractive effects on the motility of Dipylidium caninum and Fasciola hepatica. 3) Treatment with TS (6.7 X 10(-5) approximately 4.8 X 10(-4) M) had little effect on the motility of Schistosoma japonicum. 4) TS (6.7 X 10(-5) M) paralyzed the motility of the mouse isolated ileum preparation. 5) TS (6.7 X 10(-7) 6.7 X 10(-6) M) stimulated the twitch response induced by guanidine (2.5 X 10(-3) M) in the frog isolated rectus preparation. 6) Eserine and TS acted antagonistically on all preparations with the the exception of S. japonicum. 7) TS and strychnine were antagonistic in isolated host tissues, whereas these compounds acted similarly on parasitic helminths. Thus, it is suggested that some of the experiential effects of the crude extracts of Stemona such as the anthelmintic effects are caused through the action of TS on parasitic helminths and host tissues.

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.

Contractile effect of prolactin on guinea pig isolated ileum

Prolaction (PRL) at high concentrations contracted the guinea pig isolated ileum. The maximum response elicited by PRL was 44% of that of histamine-induced responses. There was no significant difference in potency between PRL preparations obtained from two different sources. PRL responses were nullified by denaturation or proteolytic digestion of the hormone. The contractile response was antagonised by atropine and potentiated by neostigmine, but unaffected by the prostaglandin antagonist SC-19220. The pA 2 values of atropine against PRL and ACh were similar. Preincubation with morphine, which inhibits ACh release, produced slight inhibition of PRL-evoked contractions. Even high concentration of PRL failed to produce any response in neostigmine-treated frog rectus muscle preparations. This suggests that PRL may produce contractions through a cholinergic mechanism involving muscarinic receptors. Enhanced gut motility reported earlier for hyperprolactinemic states may be attributed to this cholinomimetic effect of PRL on the intestinal tract.

Chemiluminescent determination of acetylcholine, and continuous detection of its release from torpedo electric organ synapses and synaptosomes

A chemiluminescent procedure to determine acetylcholine is described. The enzyme choline oxidase recently purified, oxidises choline to betaine, the H 2O 2 generated is continuously measured with the luminol-peroxidase chemiluminescent reaction for H 2O 2. Other chemi or bioluminescent detectors for H 2O 2 would probably work as well. The chemiluminescent step provides great sensitivity to the method which is slightly less sensitive than the leech bio-assay but much more sensitive than the frog rectus preparation. The specificity of the chemiluminescent method depends on the fact that choline oxidase receives its substrate only when acetylcholine is hydrolysed by acetylcholinesterase. The acetylcholine content of tissue extracts was determined with the chemiluminescent method, and with the frog rectus assay, the values found were very comparable. The chemiluminescent procedure was used to follow the release of acetylcholine from tissues. When a slice of electric organ is incubated with choline oxidase, luminol and peroxidase, KCl depolarization or electrical stimulation in critical experimental conditions triggered an important light emission, which was blocked in high Mg 2+. The venom of Glycera convoluta, known to induce a substantial transmitter release, was also found to trigger the light emission from tissue slices. Suspensions of synaptosomes release relatively large amounts of acetylcholine following Glycera venom action; this was confirmed with the chemiluminescent reaction. The demonstration that the light emission reflects the release of acetylcholine is supported by several observations. First, when the tissue is omitted no light emission is triggered after KCl or venom addition to the reagents. Second, the time course of the light emission record is very similar to the time course previously found for ACh release with radioactive methods. Third, if choline oxidase is omitted, or if acetylcholinesterase is inhibited by phospholine, the light emission is blocked, showing that the substance released has to be hydrolyzed by acetylcholinesterase and oxidised by choline oxidase to generate chemiluminescence. The procedure described has important potential applications since other transmitters can similarly be measured upon changing the oxidase.

The effect of sodium bisulphite on nicotinic cholinoceptors in the frog rectus abdominis muscle

The effect of sodium bisulphite on nicotinic cholinoceptors in the frog rectus abdominis muscle

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.

Pharmacological effects of a Peruvian scorpion ( Hadruroides lunatus) venom

Hadruroides lunatus venom has a low lethality in mice ( ld 50, 68 mg/kg i.p.) and in dogs induces a fall in blood pressure which is prevented by an antihistaminic. The venom liberates acetylcholine and potentiates acetylcholine and serotonin actions in the rat ileum. It does not affect rat phrenic nerve-diaphragm nor toad rectus abdominis isolated preparations, but increases basal tone of the isolated atrium of the rat.

The effects of substituted benzamides on frog rectus abdominis

The substituted benzamides metoclopramide, bromopride, tiapride and sulpride (10 −5 and 10 −4 M) significantly increased the sensitivity of frog rectus abdominis muscle to exogenous acetylcholine but not to carbachol. This supersensitivity could be correlated with the anticholinesterase activity of these drugs measured in homogenates from frog skeletal muscle. Sultopride, like aprocainamide, has only inhibitory effect on the responses of the rectus adnominis to acetylcholine and has n anticholinesterase activity in this preparation.

Morphological characteristics and stimulus-secretion coupling in bovine adrenal chromaffin cell cultures

Chromaffin cells isolated from adult bovine adrenal medullae were plated on collagen-coated dishes in Dulbecco's modified Eagle's medium containing 10% fetal calf serum. After 8–16 h in culture, the chromaffin cells had started to develop one, two or, more rarely, three neurites. The neurites grew at a rate of7.25 ± 0.07μm/day showing a linear correlation between process length and age of the culture. The neurites displayed one or more varicosity-like structures. Some neurites made long lasting contacts with other cell bodies and processes. Cytochemical tests indicated positive catecholamine fluorescence in boti cell bodies and processes. Fluorometric determinations indicated that by day 7 the catecholamine content was75.7 ± 1% of that found on day 1 and that noradrenaline and adrenaline represented24.6 ±1% and75.3 ± 1% of the total amine content respectively. Catecholamines were released from these cultured chromaffin cells in response to stimulation by either 56 m m KCl or acetylcholine. The stimulation-induced release of amines was Ca 2+-dependent and was blocked by increasing the extracellular c oncentration of Mg 2+. Substitution of (a) extracellular Na 2+ by either choline or sucrose or (b) Ca 2+ by Ba 2+ produced a sharp increase in catecholamine output. Acetylcholine produced a doserelated increase in catecholamine release; half maximal release was produced by3.5 × 10 −5 m acetylcholine and maximal release by 10 −4 m acetylcholine. The cholinergic receptor of cultured chromaffin cells appears to be nicotinic since catecholamine release was stimulated by nicotine and carbamylcholine but not by pilocarpine. Acetylcholine-evoked catecholamine release was blocked by d-tubocurarine (ID 50 = 5.5 × 10 −7 m), and by hexamethonium (ID 50 = 8 × 10 −6 m). However, the acetylcholine-evoked amine release was not blocked by α-bungarotoxin at a concentration (1.25 × 10 −7 m) which blocked frog rectus abdominus responses to acetylcholine (10 −6–10 −3 m). Tetrodotoxin (5 × 10 −6 m) produced47 ± 2% inhibition of the secretory response to acetylcholine (10 −4 m) but it did not modify the amine release in response to 56 m m KCl. Adult bovine chromaffin cells in culture display some of the morphological and functional characteristics of sympathetic neurones. Consequently, the bovine chromaffin cell in culture appears to be a promising model for studies on development and secretion.

A comparison of cinobufotenine (the quaternary derivative of 5-HT) and some related compounds with coryneine (the quaternary derivative of dopamine) on the frog rectus, guinea-pig ileum and rat fundus strip preparations.

1 Coryneine is 2.7 times as active as cinobufotenine on the frog rectus but on the guinea-pig ileum cinobufotenine is 1.5 times as active as coryneine. Cinobufotenine is a potent stimulant of parasympathetic ganglia and its effect are competitively antagonized by hexamethonium. 2 The effects of pH on activity relative to a standard whose ionisation is constant (Me4+N or the trimethylammonium analogue of tryptamine) are consistent with the phenate form being weaker than the phenolic form but the changes are smaller than with coryneine because cinobufotenine is a weaker acid. 3 The hydroxyl group makes a large contribution to activity. Cinobufotenine is 9 times as active as the analogue without a hydroxyl on the frog rectus and 12 times as active as it on the ileum. The 5-methoxy analogue is an antagonist on the frog rectus and a very weak partial agonist on the ileum. 4 Cinobufotenine and the quaternary derivative of tryptamine have less than one-thousandth of the activity of 5-hydroxytryptamine on the rat fundus strip.

Potentiation and inhibition of nicotinic effects on striated muscle by the tetramine disulfide benextramine.

In low concentrations (0.3-3 muM) the tetramine disulfide benextramine (BHC; N,N'-bis[6-(o-methoxybenzylamino)-n-hexyl]cystamine) potentiated the contracture of the isolated frog rectus abdominis muscle caused by acetylcholine but in the presence of physostigmine or in a higher concentration (10 muM) it inhibited. Benextramine only inhibited the contracture caused by carbachol or butyrylcholine. The all-carbon analog of benextramine only inhibited the effect of acetylcholine. The inhibitory effects of benextramine and its carbon analog were noncompetitive and readily reversible but the potentiating effect of benextramine was not readily reversible.

Toxicology and pharmacology of some ruthenium compounds: Vascular smooth muscle relaxation by nitrosyl derivatives of ruthenium and iridium.

A series of compounds were synthesized from ruthenium trichloride, and their ip LD50s were determined in mice: pentamminenitrosylruthenium(II) chloride, 8.9; chloronitrobis(2,2'-dipyridyl)ruthenium(II), 55;dichlorobis(2,2'-dipyridyl)ruthenium(II), 63; ruthenium trichloride, 108; and potassium pentachloronitrosylruthenate(II), 127 mg/kg. The two bis-bipyridyl complexes produced death in convulsions within minutes, whereas the remaining compounds resulted in long, debilitating courses with death occurring in 4-7d. When given in massive overdoses, however, the compounds with inorganic ligands also produced rapid convulsive death in mice, and when given iv to anesthetized cats, they produced respiratory arrest. The major toxic effects of all the complexes appeared to be due to the metal and not to its associated ligands. Only complexes having nitrosyl ligand specifically relaxed vascular smooth muscle. Potassium pentabromoiridate(III) also relaxed rabbit aortic strips that had been contracted by adrenergic agonists, but potassium pentachloroiridate(III) did not. None of the complexes was as active as nitroprusside in relaxing aortic strips or in decreasing arterial blood pressure in cats. No compound tested was as potent as cisplatin in antitumor activity. The pentamminenitrosylruthenium(II) complex also relaxed guinea pig ileum and frog rectus abdominus when these isolated muscles had been contracted by acetylcho line. It appears that these organoruthenium compounds may produce death in central respiratory arrest, as do the inorganic complexes when given iv or ip in massive overdoses. In minimally lethal doses, the complexes with inorganic ligands may affect a variety of contractile tissues, perhaps by a general mechanism involving Ca. These complexes are apt to be generally cytotoxic as well.

回虫筋の薬理学的反応の特異性

To investigate the pharmacological properties of Ascaris muscle, comparative studies were undertaken on the actions of various drugs on Ascaris muscle, guinea pig isolated ileum and frog isolated rectus preparations. In Ascaris muscle and frog isolated rectus preparations, the contractile activities with acetylcholine (ACh, 10(-5) g/ml in Ascaris and 10(-6) g/ml in frog rectus) and 1, 1-dimethyl-4-phenylpiperazinium (DMPP, 10(-6) g/ml) were inhibited significantly and reversely by d-tubocurarine (d-Tc, 10(-5) g/ml) and mecamylamine (Meca, 10(-5) g/ml), and slightly by atropine (Atr, 10(-4) g/ml) and hexamethonium (C6, 10(-4) g/ml). In guinea pig isolated ileum preparation, the contractile activity with ACh (10(-6) g/ml) was inhibited markedly and reversely but Atr (10(-6) g/ml), while the activity with DMPP (10(-6) g/ml) was similarly inhibited by Meca (10(-6) g/ml), C6 (10(-6) g/ml) and Atr (10(-6) g/ml). Although frog isolated rectus preparation was contracted with 4-(m-chlorophenylcarbamoyloxy)-2-butynyltrimethylammonium (McN-A-343, 10(-5) g/ml) but not with pilocarpine (10(-4) g/ml), Ascaris muscle preparation was not affected by these agonists. Frog isolated rectus preparation was contracted with 5-hydroxytryptamine (5 HT, 10(-4) g/ml) but was not affected by histamine (His, 10(-3) g/ml) and gamma-aminobutyric acid (GABA, 10(-4) g/ml), whereas Ascaris muscle was contracted with His (10(-3) g/ml) and relaxed with 5-HT (10(-4) g/ml) and GABA (10(-5) g/ml). These results suggest that Ascaris muscle as well as skeletal muscle have nicotinic receptors and that the Ascaris muscle has properties which differ specifically from skeletal muscle.

On α-bungarotoxin and cobra α-toxin in estimating affinity and efficacy of full agonists

1. 1. Under isometrically recorded tension, α-bungarotoxin and cobra α-toxin in a limited range of concentrations induced a parallel shift in the dose-response curves of acetylcholine, carbacholine and suberyldicholine with no decrease in the maximum response of the chick biventer cervicis muscle. 2. 2. With irreversible occupation of cholinoreceptors of less than 93–95% by neurotoxin, the ability of acetylcholine and carbacholine to induce maximum response of the frog rectus abdominis muscle was not abolished. 3. 3. The mode of action of α-bungarotoxin and cobra α-toxin on skeletal muscle acetylcholine receptors is irreversible, competitive blockade, which makes it possible to use them for affinity and efficacy estimation of full agonists.

121) - Potentiation of caffeine-contracture by verapamil in frog rectus abdominis muscle.

121) - Potentiation of caffeine-contracture by verapamil in frog rectus abdominis muscle.

94 - Neuropharmacological studies on L-ascorbic acid and Zn2+ (1) Effects of L-ascorbic acid and Zn2+ on the isolated guinea pig ileum and frog rectus preparations

94 - Neuropharmacological studies on L-ascorbic acid and Zn2+ (1) Effects of L-ascorbic acid and Zn2+ on the isolated guinea pig ileum and frog rectus preparations

Antagonism by some beta-adrenoceptor-blocking agents to cholinergic stimulation of skeletal muscle in vitro.

Antiacetylcholine activity some beta-adrenoceptor-blocking drugs was investigated using isolated guinea pig cremaster muscle and frog fectus abdominis muscle. On the cremaster muscle, the antagonism to acetylcholine was non competitive in K0 1313, (+/-)-INPEA and (--)-INPEA, competitive in (+)-INPEA and functional in practolol; All three INPEA isomers, practolol and propranolol behaved as noncompetitive antagonists of acetylcholine on frog rectus muscle. Caffeine-induced contractions of this muscle were partially inhibited by propranolol but not by the other drugs. It is suggested that the beta-adrenoceptor-blocking drugs produce their antiacetylcholine action by interaction with sites on the muscle which are different from the cholinceptor, and which vary between compounds and species.