Pharmacological explanation for the medicinal use of <Emphasis Type="Italic">Juniperus excelsa</Emphasis> in hyperactive gastrointestinal and respiratory disorders

Crude extract of Juniperus excelsa (JeExt), which tested positive for the presence of anthraquinone, flavonoids, saponins, sterols, terpenes and tannin, exhibited a protective effect against castor oil-induced diarrhoea in mice at 100–1000 mg/kg. In rabbit jejunum preparations, JeExt (0.01–1.0 mg/mL) caused relaxation of spontaneous and K⁺ (80 mM)-induced contractions at similar concentrations to papaverine, whereas verapamil was relatively more potent against K⁺. JeExt (0.03–0.3 mg/mL) shifted Ca²⁺ concentration–response curves to the right, like papaverine or verapamil. JeExt (0.003–0.01 mg/mL) caused a leftward shift of isoprenaline-induced inhibitory concentration–response curves, similar to papaverine. JeExt (1.0–30 mg/kg) caused suppression of carbachol (CCh, 100 μg/kg)-induced increase in inspiratory pressure of anaesthetized rats. In guinea-pig trachea, JeExt (0.001–3.0 mg/mL) relaxed CCh (1 μM)- and high K⁺-induced contractions and shifted isoprenaline-induced inhibitory curves to the left. This study suggests that Juniperus excelsa possibly exhibits a combination of Ca²⁺ antagonist and phosphodiesterase inhibitory effects, which provides a pharmacological basis for its traditional use in disorders of gut and airways hyperactivity, such as diarrhoea, colic and asthma.     

Insight into the possible mechanism of antidiarrheal and antispasmodic activities of piperine

Piperine is a piperidine-ring containing alkaloid and a major constituent of Piper nigrum Linn. and Piper longum Linn. species, belonging to the Piperaceae family. The present study explored their mode of action in gastrointestinal disorders, such as diarrhea and colic. Piperine at the dose of 10?mg/kg provided complete protection from castor oil-induced diarrhea in mice, similar to that of loperamide. In isolated rabbit jejunum preparations, piperine exhibited concentration-dependent inhibition of spontaneous contractions with an EC₅₀ value of 149.1?μM (89.26–249.20, 95% CI). When used to treat high K⁺ (80?mM)-induced sustained contractions, piperine inhibited such contractions with an EC₅₀ value of 80.86?μM (56.10–116.50, 95% CI), which suggested a calcium channel blocking (CCB) effect. The CCB effect was further confirmed when pretreatment of the tissues with piperine (10–100?μM) caused a rightward shift in the Ca⁺⁺ concentration–response curves (CRCs) in Ca⁺⁺-free medium, similar to that caused by verapamil. Loperamide also caused the inhibition of spontaneous and high K⁺-induced contractions as well as shifted the Ca⁺⁺ CRCs to the right at concentrations of 1–10?μM. These data indicate that piperine exhibits antidiarrheal and antispasmodic activities, mediated possibly through calcium channel blockade.     

Insights into mechanisms underlying the gut and airways modulatory effects of <Emphasis Type="Italic">Swertia chirata</Emphasis>

Swertia chirata is used in folk medicine for the treatment of constipation, colic, diarrhea, and asthma. This study was carried out in order to provide a pharmacological basis for its medicinal use in gastrointestinal and respiratory disorders. Crude extract of Swertia chirata (Sc.Cr) and its fractions were studied using rabbit isolated tissue preparations. In jejunum, Sc.Cr, which tested positive for alkaloids, flavonoids, saponins, tannins, and terpenes, caused stimulation at concentrations of 0.01–1.0 mg/mL, followed by a relaxant effect at higher concentrations. In the presence of atropine, the contractile effect was blocked and only relaxation occurred. Sc.Cr inhibited high K⁺ (80 mM)-induced contractions at 0.01–10 mg/mL and shifted Ca²⁺ concentration–response curves to the right, similar to that caused by verapamil. In trachea, Sc.Cr relaxed the carbachol (1 μM) and high K⁺-induced contractions, in a pattern similar to that of verapamil. Bioassay directed fractionation revealed the separation of spasmogenic and spasmolytic components in aqueous and organic fractions, respectively. The chloroform fraction exhibited a concentration-dependent (0.1–3.0 mg/mL) bronchodilator effect. These results indicate that Swertia chirata exhibits gut excitatory and inhibitory effects, mediated through cholinergic and Ca²⁺ antagonist mechanisms, respectively, as well as bronchodilatation, via Ca²⁺ channel blockade. Thus, this study provides a sound mechanistic background for the therapeutic application of Swertia chirata in gut motility disorders, such as constipation, colic, and diarrhea, and airways hyperactivity disease, such as asthma.     

The activity of nifedipine,diltiazem, verapamil,and lidoflazine in isolated tissues: An approach to the determination of calcium channel blocking activity

A characteristic profile of activity was obtained in six isolated tissues for the calcium channel antagonists nifedipine, diltiazem, verapamil, and lidoflazine. All drugs produced relaxation of K⁺ depolarized guinea pig ileal longitudinal muscle strips and K⁺ depolarized canine coronary artery, depression of electrically stimulated basal contractions of guinea pig left atria, and depression of guinea pig right atrial rate. Also, all drugs produced parallel dextral displacement of concentration-response curves to calcium in guinea pig depolarized taenia caeci. The potency for this effect was quantified by Schild analysis yielding the following pA₂ estimates: nifedipine 9.5, diltiazem 7.65, verapamil 7.8, and lidoflazine 7.0. Nifedipine, diltiazem, and lidoflazine produced no relaxation of methoxamine-contracted rabbit aortae while weak effects were observed with verapamil at concentrations 100 times greater than those required to reverse calcium effects in other tissues. In general, nifedipine and diltiazem displayed selectivity for smooth muscle over cardiac muscle while verapamil showed the least selectivity in this regard.     

Effect of Roflumilast in airways disorders via dual inhibition of phosphodiesterase and Ca2+-channel

The bronchodilator effects of Roflumilast “a selective phosphodiesterase type-4 (PDE4)” inhibitor studied in this experimental protocol. The spiral strips of isolated guinea-pig tracheal chains mounted in organ bath and maintained in Krebs solution ventilated with carbogen at 32 °C and in Ca⁺⁺ restricted krebs solution. PDE inhibitory activity was evaluated by recording dose response curves using inhibitory effect of isoprenaline on CCh induced contractions. For confirmation of PDE inhibition the intracellular cAMP levels were also estimated. Roflumilast resulted a sharp inhibition in contractile responses of carbachol (CCh, 1 µM) and K⁺ (80 mM) and the results were almost similar to verapamil. In Ca⁺⁺ restricted Krebs solution, a rightward shift in the Ca⁺⁺ response curves observed in the tracheal chain strips which were pretreated with Roflumilast (0.001–0.003 mg/mL) and the maximum response was suppressed, similarly as with verapamil. PDE inhibitory effect of Roflumilast evaluated by recording dose-dependent (0.03–0.1 mg/mL) responses, the isoprenaline-induced inhibitory dose response curves shifted leftward similar to papaverine (PDE inhibitor). Pretreatment with Roflumilast exhibited elevated intracellular cAMP levels in tracheal strips. Findings of the experiment conclude bronchodilatory influence of Roflumilast via PDE and Ca⁺⁺ channel inhibition. Results of current experiment offers comprehensive mechanistic background of Roflumilast in future as therapeutic bronchodilator for hyperactive bronchial airway diseases.     

Insight into the bronchodilator activity of Vitex negundo

Abstract

Context: Vitex negundo Linn. (Verbenaceae) is traditionally used in hyperactive respiratory disorders.

Objective: This study explored the mechanisms underlying the effectiveness of Vitex negundo in hyperactive respiratory disorders.

Materials and methods: Crude extract of V. negundo leaves was obtained. For in vivo bronchodilatory activity in anesthetized rats, different doses (1, 3, 10, 30, and 50?mg/kg) of the crude extract of V. negundo (Vn.Cr) were tested. The underlying mechanisms were studied in isolated guinea pig tracheal strips, suspended in organ baths at 37?°C.

Results: Intravenous doses of the crude extract of Vn.Cr showed dose-dependent bronchodilatory effect (9–50%) against carbachol (CCh; 100?µg/kg)-induced bronchoconstriction, similar to aminophylline. In isolated guinea-pig tracheal strips, Vn.Crrelaxed CCh (1?µM) and high K⁺ pre-contractions with respective EC₅₀ values of 0.72 (0.48–1.10; n?=?5) and 3.38?mg/mL (1.84–6.21; n?=?4), similar to papaverine. Diltiazem also relaxed both contractions with more potency against high K⁺ pre-contraction (p?<?0.05). Pre-incubation of the tracheal strips with Vn.Cr potentiated the isoprenaline inhibitory concentration response curves (CRCs), similar to papaverine.

Discussion: The inhibitory effect against CCh and high K⁺ suggests involvement of phosphodiesterase (PDE) inhibitory pathway(s), in addition to an inhibitory effect on Ca⁺⁺ entry. This finding was further strengthened when pre-treatment of the tracheal strips potentiated the isoprenaline CRCs.

Conclusion: Results suggest Vn.Cr possesses a combination of papaverine-like PDE inhibitor and diltiazem-like Ca⁺⁺ entry blocking constituents, which partly explain its bronchodilatory effect, thus validating its medicinal importance in asthma.     

Influence of Osmolality of Solutions Used for K+ Contraction on Relaxant Responses to Pinacidil,Verapamil, Theophylline and Terbutaline in Isolated Airway Smooth Muscle

Abstract: Concentration-relaxation profiles for pinacidil, verapamil, terbutaline and theophylline were studied in guinea-pig trachealis contracted by two commonly applied techniques for K⁺ depolarization. All drugs were much less effective on contractions induced by hyperosmolar 124 mM K⁺ solution (added KCl) than on contractions elicited by an isoosmolar 124 mM K⁺ Krebs solution (substituted KCl). The maximal relaxant responses were (isoosmolar K⁺/hyperosmolar K⁺): pinacidil 100%/40%, verapamil 100%/60%, theophylline 100%/0%, terbutaline 50%/0%. Addition of mannitol to establish the same hyperosmolarity as with 124 mM KCl also produced contraction of guinea-pig trachealis. Concentration-relaxation curves for the drugs on mannitol-induced contractions had close resemblance to those obtained in hyperosmolar 124 mM K⁺ solution. When contraction was elicited by 30 mM K⁺, pinacidil showed seven times higher relaxant potency in hyperosmolar compared to isoosmolar solution, whereas the relaxant responses to verapamil, theophylline and terbutaline were not influenced by osmolality. When K⁺ depolarization is used as a tool for evaluation of drug action in airway smooth muscle, the two different techniques produce dissimilar results. The influence of hyperosmolarity pec se appears to be an important and unwanted feature when K⁺ depolarization is produced by addition of KCl.     

Gut modulatory and antiplatelet activities of Viscum cruciatum

Viscum cruciatum Sieber (Viscaceae) is widely used in folk medicine for various gastrointestinal and inflammatory disorders. The crude extract of Viscum cruciatum (VCr), which tested positive for alkaloids, flavonoids, coumarins, saponins, sterols, tannins, and terpenes, caused concentration-dependent (0.01–3.0?mg/mL) relaxation of spontaneous and K⁺ (80?mM)-induced contractions of isolated rabbit jejunum, similar to that caused by verapamil. VCr shifted the Ca²⁺ concentration–response curves to the right with suppression of the maximum response, like verapamil. In guinea-pig ileum preparations, VCr caused atropine-sensitive spasmogenic effects. When tested for its effect on human platelets, VCr inhibited the adrenaline and adenosine 5′-diphosphate (ADP)-induced human platelet aggregation at the concentration range of 0.3–1.2?mg/mL. These observations indicate the presence of spasmogenic, spasmolytic, and antiplatelet activities in Viscum cruciatum mediated through cholinergic and calcium channel antagonist activities along with the blockade of adrenergic and ADP receptors, respectively, which explains its medicinal use in gut motility and inflammatory disorders.     

Calcium Antagonistic Properties of the Sesquiterpene T-Cadinol: A Comparison with Nimodipine in the Isolated Rat Aorta

Abstract: (+)-T-Cadinol is a sesquiterpene with smooth muscle relaxing properties. In the isolated rat aorta, T-cadinol relaxed contractions induced by 60 mM K⁺ in a concentration-dependent fashion. The dihydropyridine calcium antagonist nimodipine was approximately 4,000 times more potent than T-cadinol. While both drugs nearly abolished the K⁺-induced contractions, they only partially relaxed contractions induced by phenylephrine. The relaxation induced by T-cadinol and nimodipine in K⁺-contracted aortic rings, was completely reversed by the calcium channel activator Bay K8644. In aortic preparations partially depolarized by 20 mM K⁺, Bay K8644 induced a concentration-dependent contraction. Nimodipine shifted the Bay K8644 concentration-response curve to the right in a parallel manner, consistent with a competitive mode of inhibition. T-cadinol at concentrations less than 10^?3.5 M also produced a right-ward shift of the Bay K8644 concentration-response curve with a maintained maximum response. However, the highest T-cadinol concentration used (10^?3.5 M) significantly reduced the maximum response. In conclusion, although T-cadinol and nimodipine display marked structural differences, their pharmacological profiles of action have several features in common, suggesting that T-cadinol is a calcium antagonist, possibly interacting with the dihydropyridine binding sites on the calcium channels.     

Antispasmodic and bronchorelaxant activities of Salsola imbricata are mediated through dual Ca+2 antagonistic and β-adrenergic agonistic effects

Context: Salsola imbricata Forssk. (Chenopodiaceae) has folkloric repute for the treatment of various gastrointestinal and respiratory ailments.

Objective: The present study investigates spasmolytic and bronchorelaxant effects of S. imbricata.

Materials and methods: The crude aqueous-ethanol extract of the aerial parts of S. imbricata and its fractions, in cumulative concentrations (0.01–10?mg/mL), were tested on contractions of isolated rabbit jejunum and tracheal preparations. Furthermore, concentration response curves (CRCs) of Ca⁺² and carbachol were constructed in the absence and presence of the extract. Standard organ bath methods were used.

Results: The crude extract relaxed spontaneous, K^+?(80?mM) and carbachol (1?μM)-induced contractions in jejunum preparations with respective EC₅₀ values of 0.40 (0.35–0.46), 0.69 (0.60–0.79) and 0.66 (0.57–0.75) mg/mL. It shifted Ca⁺² CRCs rightward in nonparallel manner. In isolated tracheal preparations, the crude extract caused relaxation of K^+?(80?mM) and carbachol (1?μM)-induced contractions with EC₅₀ values of 0.86 (0.75–0.98) and 0.74 (0.66–0.84) mg/mL, respectively. It displaced carbachol CRCs rightward with suppression of maximal response. In both tissues, pretreatment with propranolol (1?μM) caused rightward shift in inhibitory CRCs of the extract against carbachol-induced contractions. The ethyl acetate fraction was found more potent in relaxing smooth muscle contractions than the parent extract and its aqueous fraction.

Discussion and conclusion: The results suggest that the spasmolytic and bronchorelaxant activities of S. imbricata are related to Ca⁺² antagonistic and β-adrenergic agonistic effects, thus justifying some of the traditional uses of the plant.     

Role of Ca2+ in non-cholinergic,non-adrenergic responses to nerve stimulation of the guinea-pig small intestine

Summary The effects of calcium channel blockers (D-600, verapamil), sodium nitroprusside, papaverine, indomethacin, local anaesthetics and blockade of sodium pump activity on the non-cholinergic, non-adrenergic transmission in the guinea-pig duodenum, jejunum, proximal and terminal ileum were analysed in the presence of atropine and guanethidine.A decrease of the extracellular Ca²⁺ concentration inhibited the primary and rebound contractions but only in Ca²⁺-free solution was the primary relaxation diminished. D-600, verapamil, sodium nitroprusside and papaverine inhibited both the primary and rebound contractions to the same degree and their effects on the primary relaxation were less pronounced than on the contractions.Indomethacin dissolved in alkaline solution did not depress the non-cholinergic, non-adrenergic responses in any region of the small intestine, whereas indomethacin dissolved in ethanol antagonized both the primary and rebound contractions in the muscles.Local anaesthetics (procaine, trimecaine) in low concentrations inhibited only the primary contraction. Higher concentrations also inhibited both the rebound contraction and primary relaxation. Procaine in low concentrations did not markedly affect the non-cholinergic, non-adrenergic i.j.p.s and e.j.p.s., but did block the action potentials induced by e.j.p.s.Our findings indicate that the primary relaxation, and primary and rebound contractions are probably induced by different mechanisms and are not mediated by ATP. We confirmed that prostaglandins did not participate in the generation of the rebound contraction.This study was supported in part by JSPS Japan     

The dissociation constant of verapamil estimated from its effect on Ca concentration-tension curves in guinea-pig tracheal muscle

Concentration-tension curves for calcium ions (Ca²⁺) were studied in indomethacin-treated guinea-pig tracheal muscle in the presence of different concentrations of carbachol in media containing 5.9 mM K⁺ or 40 mM K⁺. The effect of verapamil was investigated taking into account the steepness (the Hill coefficient) of the Ca²⁺ curve. When carbachol (1 μM) was added to 40 mM K⁺ solution, the Ca²⁺ concentration to produce half maximum tension (EC₅₀) was reduced from 0.2 mM to 0.08 mM and the Hill coefficient was increased from 1.4 to 2.0, respectively. In the presence of carbachol (1 μM), the Ca²⁺ concentration-tension curve was not much influenced by increasing the K⁺ concentration from 5.9 to 40 mM K⁺. Verapamil (0.5 μM) shifted the Ca²⁺ concentration-tension curve to the right in a parallel manner under all experimental conditions, the shift being greater with curves having a smaller Hill coefficient. The dissociation constant of verapamil was not altered by carbachol when estimated from the shift of the curve if the Hill coefficient is taken into consideration. It is concluded that the relatively low susceptibility of carbachol-induced contractions to verapamil in the presence of 40 mM K⁺, compared with these produced by K⁺ alone, is not due to a decreased verapamil affinity but to improved Ca²⁺-response coupling.     

Chemical composition and vascular and intestinal smooth muscle relaxant effects of the essential oil from Psidium guajava fruit

Context: Psidium guajava L. (Myrtaceae) is widely used in traditional medicine for the treatment of various ailments including cardiovascular and gastrointestinal disorders.

Objectives: The current study investigated the chemical composition and cardiovascular and gastrointestinal effects of the essential oil of P. guajava.

Materials and methods: The chemical composition of the essential oil was investigated using gas chromatography-mass spectrometry (GC-MS) technique. The biological activity of the essential oil was tested on rabbit aorta and jejunum. All changes in isometric tension were recorded through a force transducer coupled with a bridge amplifier data acquisition system.

Results and discussion: GC-MS analysis showed the presence of butanoic acid methyl ester, 3-methyl glutaric anhydride, 1-butanol, 3-hexenal, cinnamyl alcohol, 1-hexanol and hexane as the major components. In isolated rabbit aorta preparations, the essential oil showed vasorelaxation at doses of 3-10?mg/mL against high K^+?and phenylephrine pre-contractions with EC₅₀ values of 5.52 (5–6.04) and 6.23?mg/mL (5.0–7.46). The essential oil inhibited spontaneous and high K^+?induced contractions in isolated rabbit jejunum with EC₅₀ values of 0.84 (0.3–1.38) and 0.71?mg/mL (0.3–1.12) and shifted Ca?⁺?² concentration curves to the right, similar to verapamil, suggesting spasmolytic activity mediated possibly through Ca?⁺?² channel blockade.

Conclusions: In summary, the data indicated the presence of seven different phytoconstituents in the essential oil of P. guajava and calcium channel blocking activity, which provides a pharmacological base to the traditional use of P. guajava in cardiovascular and gastrointestinal disorders. Further studies are suggested to explore the molecular nature of these effects.     

Differential vasorelaxant effects of KR-30075, a new cyclic AMP-phosphodiesterase inhibitor,on guinea-pig pulmonary,bovine coronary and renal arteries

The vasorelaxant effects of KR-30075 in guinea-pig pulmonary, bovine coronary and renal arterial strips contracted by either K⁺-depolarization, phenylephrine, or prostaglandin F_2α (FGF_2α) were evaluated. KR-30075 was more potent than imazodan as a vasorelaxant against PGF_2α-induced contractions in bovine coronary and renal arteries, whereas against K⁺-induced contractions KR-30075 was less potent than imazodan in guineapig pulmonary arteries and more potent in bovine coronary arteries. KR-30075 was more potent against contractions induced by phenylephrine or PGF_2α than the contractions induced by K⁺. This profile of activity for KR-30075 was similar to that of imazodan and dissimilar from the calcium entry blocking agent nifedipine. There was no vascular selectivity of KR-30075 between bovine coronary and renal arterial strip preparations. In conclusion, this study shows that KR-30075 represents the vasorelaxant effects on guinea-pig pulmonary, bovine coronary and renal arteries without specific vascular selectivity. The vasorelaxant profile of KR-30075, with different sources of vascular smooth muscle, is unlike that of calcium entry blocking agent and more similar to the profile of the agent that inhibit cyclic nucleotide phosphodiesterase.     

Comparison of the Effects of a New Vasodilator Pinacidil and Nifedipine on Isolated Blood Vessels

Abstract: In isolated human crural veins studied in vitro pinacidil (0.038–380 μM) caused a concentration-related inhibition of noradrenaline, 18 μM (NA) and 127 mM K⁺-induced contractions. Pinacidil was more potent in inhibiting the NA-contraction than that induced by K⁺, whereas the reverse was seen for nifedipine. At the highest concentrations greater inhibitions of the NA-induced contractions could be obtained with pinacidil than with nifedipine. The inhibitory effect of pinacidil on the K⁺-induced contractions was eliminated during a 1 hr wash-out period. In contrast to this, the inhibitory effect of nifedipine could not be eliminated during 4 hrs repeated wash-out. Pinacidil was completely devoid of inhibitory effect on ⁴⁵Ca net influx in rat aorta, whereas nifedipine caused a significant reduction of influx. The results indicate that both pinacidil and nifedipine are effective vasodilatators in human vessels. Pinacidil seems to be more effective in NA-induced contractions than does nifedipine. The mechanism of action of pinacidil cannot be attributed to an inhibitory effect on cellular calcium entry.     

汉防己甲素对气管平滑肌45Ca内流的影响

本文应用国产⁴⁵CaCl₂研究汉防已甲素(以下简称为汉甲)对气管平滑肌钙内流的影响。汉甲对犬与豚鼠气管平滑肌基础的⁴⁵Ca内流量无明显的影响;60μg/ml汉甲对犬气管平滑肌组胺兴奋与高钾打开电位操纵通道(POC)的5 min⁴⁵Ca内流量的抑制率,分别为11.1%与38.3%;60μg/ml汉甲对豚鼠气管平滑肌组胺与高钾兴奋的5min⁴⁵Ca内流量的抑制率分别为48.7%与33.3%,10μg/ml或20μg/ml汉甲虽对犬或豚鼠气管平滑肌组胺兴奋的、高钾兴奋和/或打开POC的⁴⁵Ca内流量具有一定的抑制作用,但无统计学意义。说明汉甲对气管平滑肌POC与受体操纵通道(ROC)均有阻断作用,由于对高钾兴奋和/或打开POC的⁴⁵Ca内流阻断是完全的,而对组胺兴奋和打开RCC的⁴⁵Ca内流阻断是部分的,提示汉甲优先阻断气管平滑肌的POC,60μg/ml汉甲对气管平滑肌POC的阻断强度与50μg/ml异搏定相当。汉甲的钙通道阻断作用可能与其拮抗过敏介质收缩气管的作用有关。     

KCl Contractions in the Rat Isolated Seminal Vesicle

Abstract— Potassium chloride (K⁺) produced dose-dependent contractions of the rat isolated seminal vesicle with no sign of tachyphylaxis. The contractile response was biphasic in nature and composed of an early rapid phasic contraction and a slowly developing, but more sustained, tonic response separated by a transient relaxation. Neither cocaine nor depletion of tissue catecholamines by reserpine influenced responses to K⁺. Moreover, guanethidine, phentolamine, phenoxybenzamine, atropine and physostigmine all failed to modify responses of the tissue to K⁺. Thus, the possibility of K⁺ acting via release of endogenous noradrenaline or acetylcholine is excluded. Calcium-free conditions with or without EGTA reduced both the components of K⁺-induced contraction. The rate of reduction of both responses was faster in the presence of EGTA with part of the tonic response being resistant even to calcium deprivation in the presence of EGTA. On the other hand, verapamil reduced both responses in a similar manner, whereas nifedipine produced dose-dependent rightward shifts of the concentration-response curves of both the phasic and tonic responses to K⁺. However, in the presence of nifedipine, the maximum response of only the phasic contraction was significantly lowered. It is concluded that both phases of KCl contraction in the rat seminal vesicle use extracellular Ca²⁺, of which some is tightly bound with high affinity, probably to plasma membranes. In addition, two subtypes of voltage-sensitive Ca²⁺ channels may exist, one of which is preferentially sensitive to nifedipine and both are sensitive to verapamil.     

Cholinergic-independent effects of amphetamine on mammalian skeletal muscle contractions

Studies were designed to investigate the cholinergic-independent mechanism(s) by which ( +)-amphetamine produces a biphasic modification of directly stimulated contractions of skeletal muscle in the rat phrenic nerve-diaphragm preparation. In tissues pretreated with α-bungarotoxin, low concentrations of (+)-amphetamine (2.7–10.8 × 10^?4M) enhanced muscle contractions, while higher drug levels (13.5–21.6 × 10^?4M) produced a concentration-dependent blockade. In other studies (Gerald, Meldrum and Skau, Res. Commun, chem. Path. Pharmac., 1982), high K ⁺ concentrations or low Na⁺ concentrations antagonized amphetamine-enhancement of the twitch, while potentiating the blockade; in contrast, K⁺-free media augmented amphetamine-induced enhancement of contractions. Low concentrations of amantadine, tetracaine, and tetrodotoxin increased the facilitatory response to (+)-amphetamine while the inhibitory effects of (+)-amphetamine were potentiated by higher concentrations of these antagonists; similar biphasic effects were observed with (?)-amphetamine and tetracaine. (+ )-Amphetamine reversed the marked enhancement of the twitch produced by veratridine while, conversely, this neurotoxin failed to alter muscle contractions after (+)-amphetamine pretreatment. These findings suggest that amphetamine-induced enhancement and blockade of directly-stimulated skeletal muscle resulted from alterations in Na⁺ fluxes, possibly through interactions with membrane ionic channels.     

Evaluation of bronchodialatory and antimicrobial activities of Otostegia fruticosa: A multi-mechanistic approach

Otostegia fruticosa, a plant belonging to the family Lamiaceae, is endemic to Ethiopia. In Ethiopian traditional medicine, O. fruticosa has been used for the treatment of several respiratory-related disorders. The present study was designed to evaluate the bronchodilatory and antimicrobial activities of O. fruticosa leaves crude extract (Of.Cr). Ex-vivo experiments were conducted on guinea-pig trachea provided with physiological oxygenated buffer solution using emkaBath setup. The crude extract was analyzed by gas chromatography-mass spectrometry. Of.Cr, showed the presence of terpenes, fragrance components, saponins, and higher fatty acids. Of.Cr when tested on contracted tracheal chains with carbamylcholine (CCh, 1 µM) and high K⁺ (80 mM) produced relaxation by showing higher potency against CCh with incomplete inhibition of high K⁺. Dicyclomine, used as a positive control, also showed selectively higher potency to inhibit CCh when compared with its effect against K⁺. In the anticholinergic curves, Of.Cr at 1 mg/mL deflected CCh-induced concentration–response curves (CRCs) competitively to the right like dicyclomine (0.03 µM) and atropine whereas a higher dose of Of.Cr (3 mg/mL) produced a non-parallel shift in the CCh curves like a higher dose of dicyclomine (0.1 µM). In the calcium channel inhibitory assay, Of.Cr at 3 & 5 mg/mL, deflected CRCs of Ca⁺⁺ to the right like verapamil, used as positive control. Of.Cr, at concentrations (1–3 mg/mL) increases cAMP levels in isolated tracheal homogenates, similar to positive control phosphodiesterase inhibitor (papaverine). When tested for antibacterial activity against standard and clinical strains, Of.Cr was found more active (MIC 475 µg/ml) against S. aureus (NCTC 6571), while the maximum inhibition (MIC 625 µg/ml) was observed by the extract when tested against MRSA. These results determine the mechanistic pathways of the observed bronchodilatory effect of Otostegia fruticosa with a combination of anticholinergic and dual inhibition of phosphodiesterase and voltage-gated Ca⁺⁺ channels.     

A mechanistic evaluation of the traditional uses of Nepeta ruderalis in gastrointestinal and airway disorders

Context: Nepeta ruderalis Buch.-Ham. (Lamiaceae), locally known as Badranj Boya, is an aromatic herb used traditionally as an antispasmodic, antidiarrhoeal, and anti-asthamatic remedy.

Objective: Aqueous methanolic extract of N. ruderalis was studied to investigate its traditional uses.

Materials and methods: Study was conducted from September 2015 to February 2016. In vitro spasmolytic and broncho-relaxant activity of crude extract of N. ruderalis (whole plant) was evaluated at 0.01–10?mg/mL final bath concentration in isolated rabbit jejunum and tracheal tissues, using PowerLab data acquisition system (Transonic Systems Inc., Ithaca, NY). In vivo antidiarrhoeal activity was evaluated in castor oil-induced diarrhoeal mice at the dose of 300 and 500?mg of crude extract orally.

Results: Crude extract of N. ruderalis completely relaxed spontaneously contracting, high K⁺ (80?mM) and carbachol (1?μM) induced contracted jejunum with an EC₅₀ value of 5.85 (5.45–6.27), 4.0 (3.80–4.23) and 2.86 (2.48–3.29), similar to verapamil. Nr.Cr relaxed high K⁺ and carbachol induced contractions, at 5 and 10?mg/mL with an EC₅₀ value of 2.37 (2.11–2.67) and 3.26 (2.9–3.67), respectively, and also displaced calcium concentration–response curves toward right at 0.1 and 0.3?mg/mL. Nr.Cr exhibited antidiarrhoeal protection at a dose of 300 and 500?mg/kg, similar to verapamil, whereas no acute toxicity signs were seen up to 5?g/kg in healthy mice.

Discussion and conclusion: Results suggest the presence of spasmolytic and broncho-relaxant effects in the crude extract of N. ruderalis, possibly mediated through calcium channel-blocking activity, providing the pharmacological basis for its traditional uses in gastrointestinal and airway disorders.