Differential sensitivities of the sphincter of Oddi and gallbladder to cholecystokinin in the guinea pig: their role in transsphincteric bile flow

1992 ◽  
Vol 70 (10) ◽  
pp. 1336-1341 ◽  
Author(s):  
Karen Harrington ◽  
Arieh Bomzon ◽  
Keith A. Sharkey ◽  
Joseph S. Davison ◽  
Eldon A. Shaffer
Keyword(s):  
Guinea Pig ◽  
Circular Muscle ◽  
Sphincter Of Oddi ◽  
Dependent Manner ◽  
Field Stimulation ◽  
Response Curves ◽  
Gallbladder Contraction ◽  
Concentration Dependent Manner ◽  
Cholinergic Mechanism

Cholecystokinin (CCK) is considered to simply contract the gallbladder and relax the sphincter of Oddi with meals. In this study, we examined this hypothesis by investigating the action of CCK on the sphincter of Oddi and gallbladder of the guinea pig. The experimental design used an in vitro preparation of the sphincter of Oddi to measure contraction of the circular muscle. CCK increased tone in both the gallbladder and the sphincter of Oddi in a concentration-dependent manner. The normalized concentration–response curves for CCK, however, revealed that the gallbladder had a greater sensitivity to CCK (ED50 7 nM) than the sphincter of Oddi (ED50 22 nM; p < 0.01). Conversely, the sphincter was more sensitive to bethanechol than was the gallbladder. When the sphincter of Oddi was stimulated maximally with CCK in the presence of atropine (10−6 M) or tetrodotoxin (10−6 M), the contractile response was significantly reduced (p < 0.05) although not abolished. Conversely, atropine completely abolished the responses to bethanechol (10−3 M) and transmural field stimulation (70 V, 10 Hz, 1 ms, for 20 s). Transmural field stimulation of the sphincter that had been precontracted with CCK (26 nM) caused a transient, initial relaxation followed by contraction. Pretreatment with atropine augmented the duration of this relaxation, which could be completely abolished by tetrodotoxin. Thus, CCK contracts the sphincter of Oddi in the guinea pig by a direct (myogenic) and a neural (likely cholinergic) mechanism. Relaxation of the sphincter of Oddi also occurs in the guinea pig via noncholinergic inhibitory nerves. Duodenal delivery of bile is expedited by CCK, which induces gallbladder contraction at low, near-physiological levels without stimulating the sphincter. Under other conditions, sphincter of Oddi relaxation may facilitate transsphincteric flow. In contrast, increased cholinergic tone may help prevent duodenal reflux into the biliary system.Key words: cholecystokinin, bethanechol, enteric nervous system, gallbladder function, sphincter of Oddi.

Effect of bradykinin on airway neural responses in vitro

1992 ◽  
Vol 73 (4) ◽  
pp. 1537-1541 ◽  
Author(s):  
M. Miura ◽  
M. G. Belvisi ◽  
P. J. Barnes
Keyword(s):  
Matched Control ◽  
Electrical Field Stimulation ◽  
Dependent Manner ◽  
Field Stimulation ◽  
Neural Responses ◽  
Response Curves ◽  
Electrical Field ◽  
Concentration Dependent Manner ◽  
Before And After

We investigated the effects of bradykinin (BK) on airway excitatory nonadrenergic noncholinergic (e-NANC) and cholinergic nerves in vitro. Neural responses were elicited by electrical field stimulation in guinea pig airways in vitro before and after the addition of BK (10(-10)-10(-7) M). Captopril (10(-5) M) and phosphoramidon (10(-6) M) were added to prevent degradation of BK, and all neural responses were measured in the presence of indomethacin (10(-5) M) and propranolol (10(-6) M). BK potentiated e-NANC responses in bronchi in a concentration-dependent manner (10(-10)-10(-7) M) without changing concentration-response curves to exogenously applied substance P (10(-10)-10(-5) M). BK significantly potentiated e-NANC neural constrictor responses by 22 +/- 7% at 10(-8) M (mean +/- SE, n = 5, P < 0.05) and 32 +/- 7% at 10(-7) M (n = 8, P < 0.01), compared with changes in time-matched control tissues (7 +/- 2%, n = 8). The potentiation of e-NANC responses by BK was abolished by pretreatment with a specific B2-receptor antagonist, HOE 140 (10(-7) M). Cholinergic constrictor responses elicited to electrical field stimulation were not affected by the addition of BK (up to 10(-7) M). These results suggest that BK potentiates e-NANC bronchoconstrictor responses prejunctionally via a B2-receptor.

Guinea pig visceral C-fiber neurons are diverse with respect to the K+ currents involved in action-potential repolarization

1994 ◽  
Vol 71 (2) ◽  
pp. 561-574 ◽  
Author(s):  
E. P. Christian ◽  
J. Togo ◽  
K. E. Naper
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Outward Current ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Whole Cell ◽  
C Fiber ◽  
K Current ◽  
Action Potential Repolarization

1. Intracellular recordings were made from C-fiber neurons identified by antidromic conduction velocity in intact guinea pig nodose ganglia maintained in vitro, and whole-cell patch clamp recordings were made from dissociated guinea pig nodose neurons to investigate the contribution of various K+ conductances to action-potential repolarization. 2. The repolarizing phase of the intracellularly recorded action potential was prolonged in a concentration-dependent manner by charybdotoxin (Chtx; EC50 = 39 nM) or iberiatoxin (Ibtx; EC50 = 48 nM) in a subpopulation of 16/36 C-fiber neurons. In a subset of these experiments, removal of extracellular Ca2+ reversibly prolonged action-potential duration (APD) in the same 4/9 intracellularly recorded C-fiber neurons affected by Chtx (> or = 100 nM). These convergent results support that a Ca(2+)-activated K+ current (IC) contributes to action-potential repolarization in a restricted subpopulation of C-fiber neurons. 3. Tetraethylammonium (TEA; 1-10 mM) increased APD considerably further in the presence of 100-250 nM Chtx or Ibtx, or in nominally Ca(2+)-free superfusate in 14/14 intracellularly recorded C-fiber neurons. TEA affected APD similarly in subpopulations of neurons with and without IC, suggesting that a voltage-dependent K+ current (IK) contributes significantly to action-potential repolarization in most nodose C-fiber neurons. 4. Substitution of Mn2+ for Ca2+ reduced outward whole-cell currents elicited by voltage command steps positive to -30 mV (2-25 ms) in a subpopulation of 21/36 dissociated nodose neurons, supporting the heterogeneous expression of IC. The kinetics of outward tail current relaxations (tau s of 1.5-2 ms) measured at the return of 2-3 ms depolarizing steps to -40 mV were indistinguishable in neurons with and without IC, precluding a separation of the nodose IC and IK by a difference in deactivation rates. 5. Chtx (10-250 nM) reduced in a subpopulation of 3/8 C-fiber neurons the total outward current elicited by voltage steps depolarized to -30 mV in single microelectrode voltage-clamp recordings. TEA (5-10 mM) further reduced outward current in the presence of 100-250 nM Chtx in all eight experiments. The Chtx-sensitive current was taken to represent IC, and the TEA-sensitive current, the IK component contributing to action-potential repolarization. 6. Rapidly inactivating current (IA) was implicated in action-potential repolarization in a subpopulation of intracellularly recorded C-fiber neurons. In 4/7 neurons, incremented hyperpolarizing prepulses negative to -50 mV progressively shortened APD.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of ω-hydroxylase product on distal human pulmonary arteries

2008 ◽  
Vol 294 (3) ◽  
pp. H1435-H1443 ◽  
Author(s):  
Caroline Morin ◽  
Christelle Guibert ◽  
Marco Sirois ◽  
Vincent Echave ◽  
Marcio M. Gomes ◽  
...  
Keyword(s):  
Pulmonary Arteries ◽  
Rho Kinase ◽  
Dependent Manner ◽  
Response Curves ◽  
Inhibitory Protein ◽  
Concentration Dependent Manner ◽  
Intracellular Process ◽  
Free Arachidonic Acid ◽  
Kinase Pathway

The aim of the present study was to provide a mechanistic insight into how 20-hydroxyeicosatetraenoic acid (20-HETE) relaxes distal human pulmonary arteries (HPAs). This compound is produced by ω-hydroxylase from free arachidonic acid. Tension measurements, performed on either fresh or 1 day-cultured pulmonary arteries, revealed that the contractile responses to 1 μM 5-hydroxytryptamine were largely relaxed by 20-HETE in a concentration-dependent manner (0.01–10 μM). Iberiotoxin pretreatments (10 nM) partially decreased 20-HETE-induced relaxations. However, 10 μM indomethacin and 3 μM SC-560 pretreatments significantly reduced the relaxations to 20-HETE in these tissues. The relaxing responses induced by the eicosanoid were likely related to a reduced Ca2+ sensitivity of the myofilaments since free Ca2+ concentration ([Ca2+])-response curves performed on β-escin-permeabilized cultured explants were shifted toward higher [Ca2+]. 20-HETE also abolished the tonic responses induced by phorbol-ester-dibutyrate (a PKC-sensitizing agent). Western blot analyses, using two specific primary antibodies against the PKC-potentiated inhibitory protein CPI-17 and its PKC-dependent phosphorylated isoform pCPI-17, confirmed that 20-HETE interferes with this intracellular process. We also investigated the effect of 20-HETE on the activation of Rho-kinase pathway-induced Ca2+ sensitivity. The data demonstrated that 20-HETE decreased U-46619-induced Ca2+ sensitivity on arteries. Hence, this observation was correlated with an increased staining of p116Rip, a RhoA-binding protein. Together, these results strongly suggest that the 20-hydroxyarachidonic acid derivative is a potent modulator of tone in HPAs in vitro.

scholarly journals Phytochemical Evaluation of Lythrum Salicaria Extracts and Their Effects on Guinea-Pig Ileum

2013 ◽  
Vol 8 (9) ◽  
pp. 1934578X1300800 ◽  
Author(s):  
Tímea Bencsik ◽  
Loránd Barthó ◽  
Viktor Sándor ◽  
Nóra Papp ◽  
Rita Benkó ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Ethyl Acetate ◽  
Water Extract ◽  
Lythrum Salicaria ◽  
Dependent Manner ◽  
Guinea Pig Ileum ◽  
Concentration Dependent Manner ◽  
Ethanol In Water

n-Hexane, chloroform, ethyl acetate and 50% ethanol in water extracts prepared from the air-dried flowering parts of Lythrum salicaria L. were tested for in vitro pharmacological properties on Guinea-pig ileum, which is suitable for detecting a whole range of neuronal and smooth muscle effects. UHPLC-MS was used to evaluate polyphenol components of the extracts. In the ileum, the most prominent response (46.4% related to 0.5 μM histamine) of the extracts causing smooth muscle contractions were triggered by the 50% ethanol in water extract in a concentration-dependent manner. Atropine, indomethacin and PPADS plus suramin significantly reduced the contractile response caused by this extract. The strongest inhibition was due to atropine. The results suggest that L. salicaria extracts have a moderate muscarinic receptor agonist effect in Guinea-pig ileum and that prostanoids and purinoceptor mechanisms are involved to some extent. Therefore diluted extracts of L. salicaria p.o. could be used as a mild stimulant of gastrointestinal motility. The 50% ethanol in water extract was rich in polyphenols. n-Hexane, chloroform and ethyl acetate extracts failed to contain catechin, caffeic acid, quercetin-3-D-galactoside and rutin, but they all showed spasmogenic effects, and, therefore we do not think that these compounds could be involved in the spasmogenic activity.

In vitro myometrial inhibition by the partitioned aqueous fraction of Anthocleista djalonensis leaves

2010 ◽  
Vol 88 (9) ◽  
pp. 880-887
Author(s):  
Enitome Evi Bafor ◽  
Lucky Osaro Okunrobo
Keyword(s):  
Uterine Contraction ◽  
Calcium Influx ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Response Curves ◽  
Concentration Dependent Manner ◽  
Aqueous Fraction ◽  
Uterine Contractions ◽  
Β Adrenergic Receptors

This study investigated the effect on the uterus of the aqueous fraction of the partitioned methanol crude extract of the leaves of Anthocleista djalonensis (AD) and the possible mechanism of AD activity. AD inhibited the concentration–response curves induced by oxytocin and CaCl2 on the rat uterus in vitro and significantly reduced the EC50 in a concentration-dependent manner (p < 0.05). A similar effect was observed with salbutamol and verapamil on the concentration–response curves obtained for oxytocin and CaCl2. The inhibitory effect of AD was not attenuated in the presence of propranolol. AD, salbutamol, and verapamil also produced a concentration-dependent relaxation on K+-induced sustained uterine contraction. In Ca2+-free medium, AD and salbutamol similarly inhibited oxytocin-induced contraction, but verapamil failed to produce this effect. The present results suggest that AD, being a mixture of phytochemicals, probably exerts inhibitory activity on in vitro uterine contractions of the nonpregnant, diethylstilboestrol-treated rat by multiple mechanisms that do not involve interaction with β-adrenergic receptors and do not solely depend on inhibition of calcium influx.

Neural and myogenic effects of leukotrienes C4, D4, and E4 on canine bronchial smooth muscle

1994 ◽  
Vol 266 (4) ◽  
pp. L414-L425 ◽  
Author(s):  
A. Abela ◽  
E. E. Daniel
Keyword(s):  
Smooth Muscle ◽  
Receptor Antagonist ◽  
Contractile Activity ◽  
Neuromuscular Control ◽  
Dependent Manner ◽  
Gamma Glutamyl Transpeptidase ◽  
Response Curves ◽  
Bronchial Smooth Muscle ◽  
Concentration Dependent Manner

The leukotrienes (LTs), referred to as the slow-reacting substance of anaphylaxis (SRS-A), are reported to have little or no activity in the canine airway. The objective of this study was to determine whether LTC4, LTD4, and LTE4 (10(-10)-10(-7) M) play a role in neuromuscular control of third- to fifth-order canine bronchi. In the presence of 1 microM indomethacin (Indo), canine bronchial smooth muscle contracted and was depolarized in a concentration-dependent manner by LTC4 or LTD4 but not by LTE4. LTC4 and LTD4 concentration-response curves were not significantly affected when conducted in the presence of any of the following: 10(-7) M propranolol (beta-adrenoceptor antagonist), 10(-6) M chlorpheniramine (H1-receptor antagonist), 10(-6) M ketanserin (nonselective 5-hydroxytryptamine receptor antagonist), 10(-7) M atropine (muscarinic receptor antagonist), and 10(-6) M tetrodotoxin (sodium channel blocker). LTC4 and LTD4 also potentiated electrical field-stimulated (EFS) excitatory junction potentials (EJPs), suggesting a possible prejunctional enhancement of acetylcholine release. In the absence of Indo, no postjunctional responses to LTC4 and LTD4 occurred. Endogenous prostaglandin E2 (PGE2) and 6-keto-PGF1 alpha (a stable metabolite of PGI2) levels from canine bronchi were significantly reduced by Indo. In the presence of Indo, addition of > or = 10(-8) M of PGE2 suppressed contractions to LTC4 and LTD4. These data suggest that the decrease in PGE2 and PGI2 production by Indo is sufficient to unmask the excitatory postjunctional actions of LTC4 and LTD4 on bronchial smooth muscle. Serine borate (45 mM; an inhibitor of gamma-glutamyl transpeptidase, which prevents the conversion of LTC4 to LTD4) increased selectively the contractile activity of LTC4. L-Cysteine (3 mM; an inhibitor of an aminopeptidase, which prevents the conversion of LTD4 to LTE4) enhanced the contractile responses to LTD4. Serine borate increased the amplitude and duration of EFS contractions and potentiated the amplitude of EFS EJPs; the last effects were prevented by nordihydroguaiaretic acid. These and other studies suggest that LTs are synthesized by canine bronchi and have receptors on canine bronchial smooth muscle but that contractions to LTC4 and LTD4 in the canine airway are usually not observed because of the presence of inhibitory prostanoids (PGE2 and PGI2). We suggest that decreases in PGE2 and PGI2 in models of airway disease in combination with increases in LTC4, LTD4, and thromboxane A2 may contribute to airway hyperresponsiveness in vitro.

scholarly journals The Spasmolytic, Bronchodilator, and Vasodilator Activities of Parmotrema perlatum Are Explained by Anti-Muscarinic and Calcium Antagonistic Mechanisms

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6348
Author(s):  
Musaddique Hussain ◽  
Hazoor Bakhsh ◽  
Shahzada Khurram Syed ◽  
Malik Saad Ullah ◽  
Ali M. Alqahtani ◽  
...  
Keyword(s):  
Therapeutic Option ◽  
Vascular Diseases ◽  
Experimental Models ◽  
Dependent Manner ◽  
Response Curves ◽  
Concentration Dependent Manner ◽  
Parallel Shift ◽  
Dual Blockade ◽  
Underlying Mechanisms

Parmotremaperlatumis traditionally used in different areas of Pakistan to treat gastrointestinal, respiratory, and vascular diseases. This study evaluates the underlying mechanisms for traditional uses of P. perlatumin diarrhea, asthma, and hypertension. In vitro pharmacological studies were conducted using isolated jejunum, trachea, and aortic preparations, while the cytotoxic study was conducted in mice. Crude extract of P. perlatum(Pp.Cr), comprising appreciable quantities of alkaloids and flavonoids, relaxed spontaneously contracting jejunum preparation, K+ (80 mM)-induced, and carbachol (1 µM)-induced jejunum contractions in a concentration-dependent manner similar to dicyclomine and dantrolene. Pp.Cr showed a rightward parallel shift of concentration-response curves (CRCs) of Cch after a non-parallel shift similarto dicyclomine and shifted CRCs of Ca+2 to rightward much likeverapamil and dantrolene, demonstrating the coexistence of antimuscarinic and Ca+2 antagonistic mechanism. Furthermore, Pp.Cr, dicyclomine, and dantrolene relaxed K+ (80 mM)-induced and Cch (1 µM)-induced tracheal contractions and shifted rightward CRCs of Cch similar to dicyclomine, signifying the dual blockade. Additionally, Pp.Cr also relaxed the K+ (80 mM)-induced and phenylephrine (1 µM)-induced aortic contraction, similarly to verapamil and dantrolene, suggesting Ca+2 channel antagonism. Here, we explored for the first time thespasmolytic and bronchodilator effects of Pp.Crand whether they maybe due to the dual blockade of Ca+2 channels and muscarinic receptors, while the vasodilator effect might be owing to Ca+2 antagonism. Our results provide the pharmacological evidence that P. perlatumcould be a new potential therapeutic option to treat gastrointestinal, respiratory, and vascular diseases. Hence, there is a need for further research to explore bioactive constituent of P. perlatumas well as further investigation by suitable experimental models are required to further confirm the importance and usefulness of P. perlatumin diarrhea, asthma, and hypertension treatment.

Altered contractility of circular and longitudinal muscle in TNBS-inflamed guinea pig ileum

1997 ◽  
Vol 272 (5) ◽  
pp. G1258-G1267 ◽  
Author(s):  
J. P. Martinolle ◽  
R. Garcia-Villar ◽  
J. Fioramonti ◽  
L. Bueno
Keyword(s):  
Guinea Pig ◽  
Dose Range ◽  
Circular Muscle ◽  
Maximal Response ◽  
Guinea Pig Ileum ◽  
Trinitrobenzenesulfonic Acid ◽  
Response Curves ◽  
Contractile Responses ◽  
Guinea Pig Model

Intestinal motility disorders are often associated with gut inflammation. We evaluated, in vitro under isometric conditions, changes in contractility of longitudinal and circular muscle layers from guinea pig ileum after 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced ileitis. TNBS treatment did not modify length-active tension relationships for both muscle layers, whereas a significant increase in passive tension was observed in the circular muscle response to stretching. Moreover, in both control and inflamed strips at optimal stretch, concentration-response curves to KCl were similar for both layers. In contrast, contractile responses to receptor agonists were differentially altered in both layers in comparison with controls. Thus, in longitudinal strips from TNBS-treated ileum, there was a twofold increase in maximal response (Emax) induced by carbachol and histamine without modification of 50% effective concentration (EC50) values; responses to 5-hydroxytryptamine (5-HT) were not modified; both alpha 1- and alpha 2-adrenoceptor-mediated responses to epinephrine were abolished. In circular strips, inflammation did not affect the Emax induced by carbachol and histamine but led to increased EC50 values; Emax to 5-HT was reduced without change in EC50 values. Moreover, in the dose range used (0.1 nM to 0.1 mM), a maximal response to carbachol was not obtained in inflamed circular strips. The results indicate that in the guinea pig model of TNBS-induced ileitis, the in vitro contractile responses of circular and longitudinal smooth muscle to the stimulation of various receptors are differentially altered, whereas non-receptor-mediated contraction to KCl depolarization is not modified.

scholarly journals Protective effect of aronia melanocarpa fruit juice in a model of cisplatin-induced cytotoxicity in vitro

Folia Medica ◽  
2013 ◽  
Vol 55 (3-4) ◽  
pp. 76-79 ◽  
Author(s):  
Stefka V. Valcheva-Kuzmanova ◽  
Anna B. Beronova ◽  
Georgi Tz. Momekov
Keyword(s):  
Protective Effect ◽  
Fruit Juice ◽  
In Vitro Cytotoxicity ◽  
Dependent Manner ◽  
Cellular Viability ◽  
Platinum Drug ◽  
Response Curves ◽  
Concentration Dependent Manner ◽  
Aronia Melanocarpa

ABSTRACT AIM: The aim of the present study was to investigate the protective potential of Aronia melanocarpa fruit juice in a model of cisplatin-induced cytotoxicity in the human embryonal kidney cell line HEK293T. MATERIALS AND METHODS: The cellular viability was assessed using the MTT-dye reduction assay based on the reduction of the yellow tetrazolium dye MTT to a violet formazan product via the mitochondrial succinate dehydrogenase in viable cells. Cisplatin was applied in various concentrations either alone or after a 24-hour pretreatment of the cells with Aronia melanocarpa fruit juice at 0.1 and 0.05 mg/ml. The half maximal inhibitory concentrations (IC50 values) were derived from the concentration-response curves to cisplatin. RESULTS: Applied alone, the anticancer drug caused a prominent decrease of cellular viability with IC50 8.3 ± 1.1 μM. The juice proved to significantly ameliorate the in vitro cytotoxicity of the platinum drug, in a concentration-dependent manner. The pretreatment of the cells with Aronia melanocarpa fruit juice resulted in a significant increase (p < 0.001) of IC50 for cisplatin to 25.1 ± 2.7 μM (at 0.05 mg/ml) and 34.4 ± 3.4 μM (at 0.1 mg/ml), respectively. CONCLUSION: The protective effect of Aronia melanocarpa fruit juice observed in this study is most probably due to its well appreciated antioxidant activity as oxidative stress plays a central role in the toxic effects of cisplatin.

scholarly journals Spasmolytic Action of the Methanol Extract and Isojuripidine from Solanum asterophorum Mart. (Solanaceae) Leaves in Guinea-Pig Ileum

2006 ◽  
Vol 61 (11-12) ◽  
pp. 799-805 ◽  
Author(s):  
Rita de Cassia Meneses Oliveira ◽  
Julianeli T. Lima ◽  
Luciano A. A. Ribeiro ◽  
Joelmir L. V. Silva ◽  
Fabio S. Monteiro ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Methanol Extract ◽  
Calcium Influx ◽  
Maximum Effect ◽  
Dependent Manner ◽  
Guinea Pig Ileum ◽  
Response Curves ◽  
Concentration Dependent Manner ◽  
Control Curve ◽  
Spasmolytic Action

Abstract Solanum asterophorum Mart. (Solanaceae) is a shrub popularly known as “jurubeba-defogo” in the northeast of Brazil. In the present work, the methanol extract (SA-MeOH, 3-750 μg/mL) and isojuripidine (10-7 - 3 x 10-4 ᴍ), a steroidal alkaloid obtained from S. asterophorum Mart. leaves, inhibited phasic contractions induced by both 1 μᴍ histamine [IC50 = (225.8 ± 47.4) μg/mL and (3.5 ± 0.8) x 10-5 ᴍ] or 1μᴍ acetylcholine [IC50 = (112.5 ± 20.6) μg/mL and (2.3 ± 0.4) \ 10-5 ᴍ] in guinea-pig ileum, respectively. The extract and isojuripidine also relaxed the ileum (SA-MeOH, 1-750 μg/mL, and isojuripidine, 10-9 - 3 x 10-4 ᴍ) pre-contracted with 1 μᴍ histamine [EC50 = (101.1 ± 17.4) μg/mL and (1.2 ± 0.3) x 10-6 ᴍ] or 1 μm acetylcholine [EC50 = (136.8 ± 21.1) μg/mL and (1.9 ± 0.4) x 10-6 ᴍ] or 40 mᴍ KCl [EC50 = (149.4 d 19.5) μg/mL and (1.8 ± 0.7) x 10-6 ᴍ], respectively, in an equipotent and concentration-dependent manner. This effect is probably due to inhibition of calcium influx through voltage-operated calcium (Cav) channels. To confirm this hypothesis, we evaluated their effect on cumulative CaCl2 curves in depolarizing medium nominally without Ca2+. SA-MeOH (27, 243, 500, and 750 μg/mL) and isojuripidine (3 x 10-8, 10-6, 3 x 10-5, and 3 x 10-4 m) inhibited the contractions induced by CaCl2, in a concentrationdependent manner. The concentration-response curves to CaCl2, in the presence of SAMeOH and isojuripidine, were shifted downward in relation to a control curve in a nonparallel manner resulting in reduction of the maximum effect [Emax = (71.2 ± 9.2); (57.4 ± 9.2); (43.8 ± 3.4); (41.5 ± 2.4) and (90.6 ± 4.8); (74.7 ± 8.7); (66.4 ± 3.9); (31.3 ± 4.1)%, respectively]. SA-MeOH and isojuripidine present spasmolytic action in guinea-pig ileum due to a partially blockade of calcium influx through Cav channels.

Sign in / Sign up

Export Citation Format

Share Document