Smooth muscle relaxant activities of compounds isolated from malaysian medicinal plants on rat aorta and guinea-pig ileum

Muscle relaxant activities of six compounds isolated from Malaysian medicinal plants were investigated on the smooth muscles of the rat aorta and longitudinal muscle of the guinea-pig ileum. Except for goniothalamin, the other five compounds exhibited varying degrees of muscle relaxant activities on the two smooth muscles. Dicentrine, isocorydine, altholactone and usnic acid reduced the contractions to KCI and phenylephrine in the rat aorta, whilst atranorin slightly reduced the contractions to phenylephrine but not KCI. In addition, dicentrine and isocorydine markedly reduced the contractile response to phenylephrine in Ca²⁺-free Krebs solution. In the longitudinal muscle of the guinea-pig ileum, altholactone, atranorin, dicentrine and isocorydine inhibited to a greater extent the phasic than the tonic responses to KCI. All four compounds similarly inhibited the contractions induced by ACh. The results suggest that the relaxant activities of the compounds are attributed mainly to inhibition of Ca²⁺ influx via the calcium channels in the membrane of the smooth muscles. Furthermore, the greater sensitivity of dicentrine, isocorydine and altholactone against phenylephrine-induced contractions or KCI-induced phasic contractions are due to their abilities to inhibit intracellular Ca²⁺ release in these muscles.     

Inhibition of gastrointestinal release of acetylcholine by quercetin as a possible mode of action of Psidium guajava leaf extracts in the treatment of acute diarrhoeal disease

The electrically stimulated guinea-pig ileum and spontaneously contracting guinea-pig ileum preparations were employed in studies on the effects of an alcoholic extract and two flavonoid compounds, quercetin and quercetin-3-arabinoside, extracted from the leaves of Psidium guajava. The extract showed a morphine-like inhibition of acetylcholine release in the coaxially stimulated ileum, together with an initial increase in muscular tone, followed by a gradual decrease. The morphine-like inhibition was found to be due to quercetin, starting at concentrations of 1.6 micrograms/ml. The glycoside did not show any such action at concentrations of up to 1.28 mg/ml. The extract inhibited spontaneous contractions in the unstimulated ileum with a concentration-response relationship.     

Pharmacological activity of a procyanidin isolated from Sclerocarya birrea bark: Antidiarrhoeal activity and effects on isolated guinea-pig ileum

The antidiarrhoeal activity of a procyanidin isolated from the bark of Sclerocarya birrea was studied, using four models of experimentally induced diarrhoea in rats. The cathartic agents used were: magnesium sulphate, castor oil, arachidonic acid and prostaglandin E₂. At doses of 150 mg/kg, the procyanidin showed antidiarrhoeal activity in all the models of experimentally induced diarrhoea. The procyanidin (2.5 μg/mL-0.64 mg/mL) dose-dependently inhibited the phasic contractions of the isolated guinea-pig ileum spontaneous activity; this inhibition was significantly reduced by hexamethonium (10^?4 M ). It also modified the dose-response curves to acetylcholine in a non-competitive way, and relaxed, in a dose-dependent manner, the contractions induced by acetylcholine (10^?7 M ) and KCI (50 mM ), being five times more potent against acetylcholine. The procyanidin modified the biphasic mechanical response evoked by acetylcholine (10^?7 M ) in isolated guinea-pig ileum, inhibiting the phasic response more profoundly than the tonic one. It is concluded that the antidiarrhoeal activity of the procyanidin isolated from S. birrea bark is related to an inhibition in intestinal motility. The way in which it produces this inhibition can be related to an interference with the subsequent events evoked after muscarinic stimulation.     

Effects of leaf extract of Caesalpinia bonduc (Caesalpiniaceae) on the contractile activity of uterine smooth muscle of pregnant rats

The calcium dependency and the cholinergic effect of the leaf extract of Caesalpinia bonduc Roxb. (Caesalpiniaceae) was studied in isolated pregnant rat myometrium preparations. Isometric contractions were recorded. The extract (Cebo) increased the contractile force in the isolated strips in a concentration-dependent manner. The effects were comparable to those obtained with acetylcholine. Contractions induced by Cebo or acetylcholine were inhibited in the presence of atropine. The stimulating action of Cebo on the contractile responses of isolated myometrium preparations inhibited by atropine may be mediated by cholinergic receptors. In calcium-free solution Cebo induced a tonic contraction (contracture) of the muscle. Moreover, in high-potassium calcium-free solution Cebo caused contracture of the uterine smooth muscle. Cebo was still able to elicit contractions in calcium-free solution containing EDTA or EGTA. These findings suggest the existence of cholinergic receptors sensitive to Cebo which could influence the influx of calcium (phasic contraction) and mobilization of calcium from cellular stores (tonic contraction), both of which are responsible for the increase of contractile activity and development of the contracture of uterine smooth muscle.     

Smooth muscle contraction induced by Indigofera dendroides leaf extracts may involve calcium mobilization via potential sensitive channels

The contractile effects of the aqueous extract of the leaves of Indigofera dendroides (ID) were studied on the gastrointestinal motility in mice and isolated smooth muscle preparations obtained from rats and guinea pigs. The contractile effects of 10(-6) M acetylcholine, 80 mM KCl and 1.6 mg/ml ID were measured on the rat ileal smooth muscle exposed to calcium-free buffer or physiological solution, to determine the calcium pools mobilized by extract for activation of contraction. Acute toxicity test (LD(50)) was also carried out in mice. The result showed that ID (0.05-3.2 mg/ml) produced a concentration-dependent contraction of the guinea pig and rat ileum. These responses were not blocked by mepyramine (2.49 x 10(-9) M), verapamil (8.14 x 10(-9) M), or pirenzepine (4.7 x 10(-7) M), but were blocked completely by atropine (2.92 x 10(-9) M). A significant increase in propulsion of gastrointestinal motility was observed. Acetylcholine, KCl and ID produced contractions in Ca(2+) free media. The phasic components of the contractile responses to Ach as well as the tonic component of K(+) and ID-induced contractions were relatively resistant to short periods of calcium-free exposure. Ach, K(+) and ID still caused contractions in the presence of verapamil. The data revealed that ID-induced contractions were not mediated by histaminergic receptors, calcium channels, M1 muscarinic receptors. It also suggests that Ach mobilize Ca from some tightly bound or intracellular pool, whereas high K(+) and ID may mobilize Ca from some superficial or loosely-bound pool.     

Smooth muscle relaxant effect of kaurenoic acid,a diterpene from Copaifera langsdorffii on rat uterus in vitro

The effect of kaurenoic acid, a diterpene isolated from the oleo-resin of the popular medicinal plant Copaifera langsdorffii (Leguminaceae), was analysed on rat uterine muscle responsiveness to various drugs in vitro. Cumulative concentration-response curves to acetylcholine and oxytocin were obtained before and after incubation of uterine segments with up to 160 microm of kaurenoic acid. The maximal contractile response (E(max)) evoked by these agonists was inhibited by kaurenoic acid in a concentration-related manner; at 160 microm, kaurenoic acid depressed the E(max) of oxytocin and acetylcholine by 83% and 91%, respectively. The relaxation caused by kaurenoic acid on oxytocin-induced contraction was unaffected in the presence of tetraethyl ammonium, a compound that blocks the calcium activated potassium channels. It was partially reversed by glibenclamide (10(-5) m), an ATP-sensitive potassium channel blocker. Also, kaurenoic acid at 160 microm concentration was found to inhibit significantly the CaCl(2)-evoked contractile responses in a medium of high potassium and zero calcium. Furthermore, kaurenoic acid was found to relax the sustained tonic contraction induced by acetylcholine, oxytocin, BaCl(2) and KCl in a concentration-dependent way. However, KCl-induced tonic contraction was only weakly inhibited by kaurenoic acid. These data indicate that the diterpene, kaurenoic acid, exerts a uterine relaxant effect acting principally through calcium blockade and in part, by the opening of ATP-sensitive potassium channels.     

Effect of ambrein on smooth muscle responses to various agonists

The pharmacological effects of ambrein (isolated from ambergris) on the contractile responses induced by some agonists in smooth muscle preparations were investigated. Ambrein in the concentration range of 10, 50 and 250 μg/ml decreased the spontaneous contraction of the isolated rabbit jejunum, rat uterus and guinea-pig vas deferens. Ambrein-induced antagonism to acetylcholine (Ach) in the guinea-pig ileum was abolished when the concentration of calcium chloride in the Tyrode's solution was increased to 5 mM/l. Furthermore, ambrein did not antagonise nicotine-induced contractions in the isolated rabbit jejunum or serotonin-induced contractions in the isolated guinea-pig ileum and vas deferens or the rat uterus. However, ambrein in the concentration range of 10, 50 and 250 μg/ml antagonised prostaglandins (PGs) E₂, D₂, F_2α, and oxytocin-induced contractions in the rat uterus in vitro. Ambrein also antagonised (±) noradrenaline and (−) adrenaline-induced contractions in the isolated guinea-pig vas deferens. It is concluded that ambrein-induced non-selective dose-dependent antagonism to the effects of some agonists (Ach, adrenaline, noradrenaline, PGs and oxytocin) in some smooth muscles may be due to the ability of this compound to interfere with the mobilisation of extracellular Ca²⁺ required for muscular contractions induced by these agonists.     

The presence of cholinomimetic and calcium channel antagonist constituents in Piper betle Linn

The crude aqueous extract of Piper betle leaves (Pb.Cr) was studied for the possible presence of cholinomimetic and calcium channel antagonist constituents. Pb.Cr at doses of 1-10 mg/mL caused a moderate spasmogenic effect in isolated guinea-pig ileum and this activity was concentrated in the aqueous fraction, which was found to be about 5 times more potent. Pretreatment of the tissue with atropine (1 microM) but not hexamethonium (100 microM) completely abolished the contractile effect of the aqueous fraction indicating a cholinergic (muscarinic) mechanism. In isolated rabbit jejunum preparations Pb.Cr did not produce a significant increase in the spontaneous contractions, but instead produced a dose-dependent (0.03-3.0 mg/mL) inhibition of spontaneous activity. Activity-directed fractionation revealed that the spasmolytic action was concentrated in the ethyl acetate fraction. When tested against K(+)-induced contractions, both Pb.Cr and its ethyl acetate fraction (Pb.EtAc) caused a dose-dependent inhibition, suggesting calcium channel blockade (CCB). The potent CCB effect of the crude extract and its ethyl acetate fraction was confirmed when pretreatment of the tissue with Pb.Cr or Pb.EtAc shifted the Ca(++) dose-response curves to the right in a dose-dependent manner. These data indicate that the plant contains cholinomimetic and possible calcium channel antagonist constituents, which are concentrated in the aqueous and ethyl acetate fractions respectively. It is suggested that some of the traditional uses of this plant may be explained on the basis of these activities.     

Mechanisms underlying the antispasmodic and bronchodilatory properties of Terminalia bellerica fruit

AIM OF THE STUDY: The present investigation was carried out to provide the pharmacological basis for the medicinal use of Terminalia bellerica in hyperactive gastrointestinal and respiratory disorders. MATERIALS AND METHODS: Crude extract of Terminalia bellerica fruit (Tb.Cr) was studied in in vitro and in vivo. RESULTS: Tb.Cr caused relaxation of spontaneous contractions in isolated rabbit jejunum at 0.1-3.0mg/mL. Tb.Cr inhibited the carbachol (CCh, 1microM) and K(+) (80mM)-induced contractions in a pattern similar to that of dicyclomine, but different from nifedipine and atropine. Tb.Cr shifted the Ca(++) concentration-response curves to right, like nifedipine and dicyclomine. In guinea-pig ileum, Tb.Cr produced rightward parallel shift of acetylcholine-curves, followed by non-parallel shift at higher concentration with the suppression of maximum response, similar to dicyclomine, but different from nifedipine and atropine. Tb.Cr exhibited protective effect against castor oil-induced diarrhea and carbachol-mediated bronchoconstriction in rodents. In guinea-pig trachea, Tb.Cr relaxed the CCh-induced contractions, shifted CCh-curves to right and inhibited the contractions of K(+). Anticholinergic effect was distributed both in organic and aqueous fractions, while CCB was present in the aqueous fraction. CONCLUSIONS: These results indicate that Terminalia bellerica fruit possess a combination of anticholinergic and Ca(++) antagonist effects, which explain its folkloric use in the colic, diarrhea and asthma.     

Antispasmodic and anti-diarrhoeal effect of Satureja hortensis L. essential oil

Satureja hortensis L. (Lamiaceae) is an annual herb that is used in the traditional medicine of Iran for treating stomach and intestinal disorders. The antispasmodic activity of S. hortensis essential oil (SHEO) was assessed on contractions of isolated ileum, induced by KCl and acetylcholine, and compared with the effect of atropine and dicyclomine. SHEO inhibited the response to 80 mM KCl in a concentration-dependent manner (pD(2)=1.55+/-0.09 microg/ml; this is negative log concentration of SHEO causing 50% of maximum inhibition) and attenuating the maximum inducible response of acetylcholine concentration-response curve. Effect of SHEO on KCl was similar to that of dicyclomine. Dicyclomine (3.46 and 34.6 ng/ml) also reduced the response to acetylcholine on rat isolated ileum without altering the maximum response and shifted the acetylcholine concentration-response curve to the right by 16-fold at 34.6 ng/ml (100 nM) bath concentration, while atropine only inhibited the response to acetylcholine. This study shows that SHEO is a relaxant of rat isolated ileum. In addition to antispasmodic activity in vitro, essential oil of this plant at a dose of 0.1 ml/100 g inhibited castor oil induced diarrhoea in mice. As the inhibition of contractile overactivity of the ileum is the base of the treatment of some gastrointestinal disorders such as colic, SHEO may have clinical benefits for treatment of these conditions.     

槲皮素对平滑肌收缩性及肌球蛋白Mg~（2＋）-ATPase活性的影响

目的：研究槲皮素对平滑肌收缩性及肌球蛋白Mg2＋-ATPase活性的影响。方法：以大鼠离体小肠及胃平滑肌条为研究模型,首先考察槲皮素在高钙、低钙及正常克氏液环境中对平滑肌条收缩性的影响。然后在正常克氏液中分别观察槲皮素对新斯的明、乙酰胆碱及阿托品存在下平滑肌收缩性的影响。用孔雀绿法测定槲皮素对肌球蛋白Mg2＋-ATPase活性的影响。结果：在高钙、正常钙及低钙不同条件下,槲皮素在4～64μmol/L范围内均剂量依赖性抑制小肠、胃平滑肌收缩;槲皮素（32μmol/L）拮抗新斯的明、乙酰胆碱引起的收缩作用（P〈0.01）,且相加性协同阿托品引起的抑制收缩作用（P〈0.01）;槲皮素（25μmol/L）对不同磷酸化程度的肌球蛋白的Mg2＋-ATPase活性均具有抑制作用（P〈0.01）。结论：槲皮素对胃、肠平滑肌收缩性及平滑肌肌球蛋白的Mg2＋-ATPase活性具有明显抑制作用。     

Presence of cholinergic and calcium channel blocking activities explains the traditional use of Hibiscus rosasinensis in constipation and diarrhoea

The aqueous-ethanolic extract of the aerial parts of Hibiscus rosasinensis Linn. (Malvaceae) was studied for the possible presence of spasmogenic and spasmolytic constituents to rationalize its traditional use in gastrointestinal disorders. The crude extract (Hr.Cr) caused a concentration-dependent (1-10mg/mL) spasmogenic effect in isolated guinea-pig ileum, which was blocked in the presence of atropine (0.1 microM). In spontaneously contracting rabbit jejunum, the plant extract exhibited a weak stimulatory effect at lower doses (0.03-0.30 mg/mL) followed by an inhibitory effect at higher doses (1.0-3.0mg/mL). Pretreatment of the tissues with atropine blocked the stimulatory effect resulting in the potentiation of the spasmolytic effect. Hr.Cr (0.03-1.0mg/mL) also showed an inhibitory effect on K(+) (80 mM)-induced contractions. The calcium channel blocking activity was confirmed when Hr.Cr shifted the Ca(2+) concentration-response curves to the right, similar to verapamil. Activity-directed fractionation revealed that the spasmolytic component(s) was separated in the ethyl acetate, while the spasmogenic in the petroleum ether fraction. The aqueous fraction exhibited a combination of weak spasmogenic and spasmolytic effects. These data indicate that the crude extract contains spasmogenic and spasmolytic constituents mediating their effect through cholinergic receptors activation and blockade of Ca(2+) influx, respectively, which may explain its traditional use in constipation and diarrhoea.     

Pharmacological basis for the use of peach leaves in constipation

The aqueous crude extract (PPL.Cr) of peach leaves (Prunus persica) was studied for the possible presence of gut stimulatory constituent(s) to rationalize the folkloric use of the plant in constipation. PPL.Cr at the dose of 1-10 mg/ml caused a moderate degree of spasmogenic effect in isolated guinea-pig ileum. Pretreatment of the tissue with atropine (1 M) completely abolished the contractile effect of the plant extract similar to that of acetylcholine which is suggestive of a cholinergic mechanism. In isolated rabbit jejunum preparations, PPL.Cr produced a week spasmogenic effect followed by relaxation of the spontaneous contractions at higher doses. Bioassay-directed fractionation revealed that the spasmogenic activity was separated in the aqueous fraction, while the spasmolytic activity was concentrated in the ethyl acetate fraction. When tested against K(+)-induced contraction, both PPL.Cr and its ethyl acetate fraction (PPL.EtAc) caused a dose-dependent inhibition, suggesting calcium channel blockade (CCB). The presence of CCB in peach leaves was confirmed when pretreatment of the tissue with PPL.EtAc caused a dose-dependent rightward shift in the Ca(2+) dose-response curves, similar to that produced by verapamil. These data indicate that the plant contains spasmogenic (cholinomimetic) and spasmolytic (calcium antagonist) constituents, which are concentrated in the aqueous and ethyl acetate fractions, respectively. Furthermore, the laxative effect of the plant reported in the traditional system of medicine may be partially due to the cholinergic action, which was dominant over the spasmolytic component.     

Inhibitory effects of the sesquiterpene T-cadinol on contractile responses in the isolated guinea-pig ileum

The smooth muscle relaxing effect of the sesquiterpene T-cadinol, isolated from scented myrrh (resin of Commiphora guidottii Chiov., Burseraceae), was investigated. The compound inhibited the contractile responses in the isolated guinea-pig ileum to histamine, carbachol, Ba²⁺ and K⁺ in a concentration dependent and reversible manner. The antagonism of the receptor-mediated contractions induced by histamine and carbachol was not of a competitive type. The contractions induced by Ba²⁺- and K⁺ were somewhat more sensitive to the action of T-cadinol than the receptor mediated contractions. It is suggested that the compound may interfere with a step of the contraction sequence common to all four spasmogens.     

Reduction of agonist-induced contractions of guinea-pig isolated ileum by flavonoids

The effect of 13 flavonoids on the contraction of guinea-pig isolated ileum induced by prostaglandin E₂ (PGE₂) and leukotriene D₄ (LTD₄) have been investigated. Apigenin, quercetin and kaempferol at a concentration of 10 μM significantly (p<0.001) reduced the contraction to either agonist. Crysin and flavone antagonized only PGE₂ (p<0.01). The other flavonoids were inactive. The blocking effect of apigenin, quercetin and kaempferol against PGE₂ was also concentration- and time-dependent, and was augmented by the calcium channel blocker verapamil or by lowering the extracellular calcium to 25%, consistent with a calcium-mediated mechanism of protection which these flavonoids, at the same concentration, also showed against barium chloride (BaCl₂)- or acetylcholine (ACh)-induced contraction (p<0.05–0.001).     

Evaluation of Alstonia scholaris leaves for broncho-vasodilatory activity

The present study demonstrates that the ethanol extract of Alstonia scholaris (Apocynaceae) leaves induced pronounced bronchodilatory activity in anaesthetized rats with the probable involvement of prostaglandins. However, in vitro preparations of guinea-pig trachea did not confirm this property, indicating that bronchodilation is not due to the direct tracheal smooth muscle relaxation. The vasodilatory activity of the extract was independent of adrenergic or muscarinic receptors or prostaglandins but was mainly via endothelial-derived relaxing factor, nitric oxide. The extract inhibited the spontaneous movements of rabbit jejunum and contractile effects of acetylcholine and histamine on guinea-pig ileum. Additionally, the extract caused marked reduction of barium chloride-, potassium chloride- and calcium chloride-induced contraction on guinea-pig ileum and pulmonary artery, implying a direct interference of plant extract with the influx of calcium ions into cells. However, the extract has no detectable effect on mobilization of intracellular calcium. These results coupled with the in vivo effects of ethanol extract reveal that the Alstonia scholaris leaves possess broncho-vasodilatory activity mediated presumably by prostaglandins, calcium antagonism and endothelium-derived relaxing factor(s).     

Evidence of the mechanism of action of Erythrina velutina Willd (Fabaceae) leaves aqueous extract

Ethnopharmacological relevance

Erythrina velutina is traditionally used for sleepiness, convulsions and nervous system excitation in Brazil. Although central effects have been reported for Erythrina velutina, little is known about its mechanism of action.

Aim of the study

To investigate the pharmacological evidences of mechanism of action of Erythrina velutina leaves aqueous extract (AE).

Materials and methods

Terminal segments of the guinea-pig ileum (n = 5–8) were mounted in an organ bath and isotonic contractions were recorded. Phytochemical screening was carried out on AE.

Results

AE (0.025–2.50 mg/ml) produced contractile response in the guinea-pig ileum, yielding typical concentration–response curves (EC₅₀ = 0.63 mg/ml). Electrically evoked contractions were significantly increased in the presence of AE. AE-elicited contractions were significantly reduced by bicuculline, tetrodotoxin, atropine, verapamil or incubation in low calcium–high potassium solution. Atropine along with verapamil abolished AE contractile response. Alkaloids, catechins, steroids, flavonols, flavononols, flavonoids, phenols, saponins, tannins, triterpenoids, and xanthones were detected in AE.

Conclusions

AE contains important constituents for pharmacological activities. AE-induced contractions seem to involve GABA_A receptor activation, acetylcholine release, muscarinic receptor activation, augmentation of Ca²⁺ entry through L-type calcium channels, and calcium release from the intracellular stores. These findings provide further support for Erythrina velutina traditional uses.     

Differential antagonistic effect of hydroalcoholic extract from Hymenaea martiana hayne arzeik on kinin and other agonist-induced contractions of the isolated rat uterus and Guinea-pig ileum

This study was undertaken to evaluate the action of the hydroalcoholic extract (HE) from the bark of Hymenaea martiana on bradykinin (BK), lysyl-bradykinin (L-BK), acetylcholine (ACh), angiotensin II (AII), prostaglandin F_2a (PGF_2a), serotonin (5-HT), oxytocin (Ot) and histamine (His)-induced contractions of the isolated rat uterine muscle and guinea-pig ileum. The HE (50–200 μg/mL) added to the bath for 20 min caused a concentration-dependent rightward displacement of BK, L-BK and ACh-induced contractions in the rat uterus, allied to a discrete but significant reduction of maximal responses to the latter two agonists. By contrast, at the same range of concentrations the HE antagonized in a concentration-dependent but noncompetitive manner the contractions induced by AII, but only at high concentrations (200 μg/mL) it significantly inhibited contractions evoked by both PGF_2a and Ot, while contractile responses induced by 5-HT were not affected. In the guinea-pig ileum, the HE of H. martiana (50 and 100 μg/ml) caused a discrete rightward displacement of the BK and ACh concentration—response curves. Higher concentrations of the HE of H. martiana (200 μg/mL) caused a marked depression of BK and ACh-induced maximal responses. These findings show that the active principle(s) presents in the HE from the bark of H. martiana exhibits an interesting pharmacological profile against several neurotransmitter-induced contractions in nonvascular smooth muscles. Such actions may be relevant for supporting, at least in part, the use of this plant in folk medicine.     

砂仁提取液对离体家兔主动脉条收缩性能的影响

目的研究砂仁提取液对兔离体胸主动脉血管条的作用。方法采用家兔离体胸主动脉血管条,以不同浓度去甲肾上腺素(NE)、氯化钾(KC l)为刺激剂,观察砂仁提取液对其量效曲线的影响;以NE为血管收缩刺激剂,观察砂仁提取液对内钙释放与外钙内流的影响。结果砂仁提取液使NE与KC l的量效曲线明显右移,最大反应性降低,对KC l量效曲线的抑制作用强于NE;在无钙Kerbs液中,砂仁提取液浓度依赖性抑制NE诱导的内钙释放所诱导的血管收缩反应,对复钙后NE所致的血管持续收缩具有抑制作用的趋势。结论砂仁提取液可舒张兔主动脉条,该作用可能与钙离子拮抗有关,且对主动脉依内钙性收缩的敏感性大于依外钙性收缩;对电压依赖钙通道的拮抗作用强于受体操纵的钙通道。     

Effect of Extract of Leaf and Seed of Piper guineense on Some Smooth Muscle Activity in Rat,Guinea-pig and Rabbit

Extracts of the leaf and seed of Piper guineense were separately prepared and their pharmacological effects screened using smooth muscle of the gastrointestinal tract and uterus. The leaf extract enhanced both the frequency and tone of spontaneous contractions of rabbit jejunum and induced contraction of guinea-pig ileum, which were blocked by atropine. The seed extract had the opposite effect on rabbit jejunum, an inhibition which was antagonized by prazocin, and little or no effect on guinea-pig ileum. Both extracts had a stimulant effect on rat uterine muscle, the seed extract to a lesser extent.