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Moreira-Junior L, Leal-Cardoso JH, Cassola AC, Carvalho-de-Souza JL. State-Dependent Blockade of Dorsal Root Ganglion Voltage-Gated Na + Channels by Anethole. Int J Mol Sci 2024; 25:1034. [PMID: 38256108 PMCID: PMC10816912 DOI: 10.3390/ijms25021034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 01/09/2024] [Accepted: 01/11/2024] [Indexed: 01/24/2024] Open
Abstract
Anethole is a phenolic compound synthesized by many aromatic plants. Anethole is a substance that humans can safely consume and has been studied for years as a biologically active molecule to treat a variety of conditions, including nerve damage, gastritis, inflammation, and nociception. Anethole is thought to carry out its biological activities through direct interaction with ion channels. Anethole is beneficial for neurodegenerative Alzheimer's and Parkinson's diseases. Nevertheless, nothing has been investigated regarding the effects of anethole on voltage-gated Na+ channels (VGSCs), which are major players in neuronal function. We used cultured dorsal root ganglion neurons from neonatal rats as a source of natively expressed VGSCs for electrophysiological studies using the whole-cell patch-clamp technique. Our data show that anethole interacts directly with VGSCs. Anethole quickly blocks and unblocks (when removed) voltage-activated Na+ currents in this preparation in a fully reversible manner. Anethole's binding affinity to these channels increases when the inactive states of these channels are populated, similar to lidocaine's effect on the same channels. Our data show that anethole inhibits neuronal activity by blocking VGSCs in a state-dependent manner. These findings relate to the putative anesthetic activity attributable to anethole, in addition to its potential benefit in neurodegenerative diseases.
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Affiliation(s)
| | - Jose Henrique Leal-Cardoso
- Superior Institute of Biomedical Sciences, State University of Ceará, Campus of Itaperi, Fortaleza 607402, CE, Brazil
| | - Antonio Carlos Cassola
- Department of Physiology and Biophysics, Biomedical Sciences Institute, University of Sao Paulo, São Paulo 05508, SP, Brazil
| | - Joao Luis Carvalho-de-Souza
- Department of Anesthesiology, University of Arizona, Tucson, AZ 85724, USA;
- Department of Physiology and Biophysics, Biomedical Sciences Institute, University of Sao Paulo, São Paulo 05508, SP, Brazil
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Aali E, Ghaznavi H, Soltanpour MS, Mahmoudian M, Shafiei M. Cardioprotective Effects of Mebudipine in a Rat Model of Doxorubicin-Induced Heart Failure. IRANIAN JOURNAL OF MEDICAL SCIENCES 2021; 46:136-143. [PMID: 33753958 PMCID: PMC7966930 DOI: 10.30476/ijms.2019.82057.0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Background Mebudipine, a dihydropyridine calcium-channel blocker (CCB), shows greater time- and voltage-dependent inhibitory effects than nifedipine. Its significant negative chronotropic effects without having considerable negative inotropic properties may make it a suitable candidate for the pharmacotherapy of heart failure (HF). This study aimed to investigate the possible beneficial action of mebudipine in a rat model of HF. Methods The present study carried out in the Department of Pharmacology at the Iran University of Medical Sciences during the years of 2009-2011. An experimental model of HF was induced in male Wistar rats using doxorubicin (DOX). The rats were divided into five groups with seven animals in each group: normal control group, DOX-induced HF control groups, and treatment groups. The animals were administered DOX for 15 days. A consistent deterioration occurred after a four-week rest period. The animals were then treated with intraperitoneal mebudipine (0.5 mg/kg) and intraperitoneal amlodipine (0.35 mg/kg), as well as an equal volume of distilled water for 15 days. The plasma levels of big endothelin-1 (BET-1), creatine kinase-myocardial band (CK-MB), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), and alanine aminotransferase (ALT), as well as the clinical status (heart rate and blood pressure), were assessed before and after treatment. Statistical analysis was performed with SPSS software using parametric and nonparametric ANOVA. Results Mebudipine and amlodipine reversed the increased plasma BET-1 values in the treated animals when compared with the HF control group (0.103 and 0.112 vs 0.231 pg/mL, respectively). The increased plasma levels of AST, ALT, CK-MB, and LDH were also reversed in the HF animals that received mebudipine or amlodipine. Conclusion The administration of mebudipine to HF animals, akin to amlodipine, palliated the clinical and biochemical signs of the disease in the present study. The abstract was presented in the Iranian Congress of Physiology and Pharmacology as a poster and published in the Scientific Information Database as a supplement (2015; Vol 22).
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Affiliation(s)
- Ehsan Aali
- Department of Pharmacology, School of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran.,Gifted and Talented Students Center, Iran University of Medical Sciences, Tehran, Iran
| | - Habib Ghaznavi
- Department of Pharmacology, Zahedan University of Medical Sciences, Zahedan, Iran
| | - Mohammad Soleiman Soltanpour
- Department of Medical Laboratory Sciences, School of Paramedical Sciences, Zanjan University of Medical Sciences, Zanjan, Iran
| | - Massoud Mahmoudian
- Department of Pharmacology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Massoumeh Shafiei
- Department of Pharmacology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
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Ali El‐Remaily MAEAA, Hamad HA, Soliman AMM, Elhady OM. Boosting the catalytic performance of manganese (III)‐porphyrin complex MnTSPP for facile one‐pot green synthesis of 1,4‐dihydropyridine derivatives under mild conditions. Appl Organomet Chem 2021. [DOI: 10.1002/aoc.6238] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
| | - Hesham A. Hamad
- Fabrication Technology Research Department, Advanced Technology and New Materials Research Institute (ATNMR) City of Scientific Research and Technological Applications (SRTA‐City), New Borg El‐Arab City Alexandria Egypt
- Biological and Chemical Research Centre, Faculty of Chemistry University of Warsaw Warsaw Poland
| | | | - Omar M. Elhady
- Department of Chemistry, Faculty of Science Sohag University Sohag Egypt
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Zolfaghari Z, Vatanparast J. Thymol provokes burst of action potentials in neurons of snail Caucasotachea atrolabiata. Comp Biochem Physiol C Toxicol Pharmacol 2020; 228:108654. [PMID: 31683013 DOI: 10.1016/j.cbpc.2019.108654] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/27/2019] [Accepted: 10/29/2019] [Indexed: 12/15/2022]
Abstract
Thymol, a phenolic monoterpene, is well known for its antimicrobial, antifungal and antioxidant properties. In spite of wide use in oral care products, pharmaceutical and cosmetic preparation and in food industry, the effects of thymol on the neuronal activity and intrinsic properties have not been well studied. We studied the effects of thymol on the spontaneous activity and action potential properties of central neurons of snail Caucasotachea atrolabiata. Thymol (1 mM) altered action potentials characteristics and provoked epileptiform burst firing in snail neurons, which were partially reversible after washout. Before burst firing, action potentials had lower amplitude and maximum rising slope, while the threshold voltage was raised. These results suggest the inhibition of ion channels underlying action potential initiation and upstroke. The maximum falling slope and afterhyperpolarization were also considerably reduced, suggesting the inhibition of potassium channels. Thymol (0.5 mM) that was not able to induce burst firing in snail neurons, synergistically acted with potassium channel blocker, tetraethyl ammonium, to induce burst firing, which also supports the importance of potassium channel inhibition, especially delayed rectifier potassium channels, to the thymol-induced alteration of firing pattern. The thymol-induced burst firing seems to be dependent on both sodium and calcium currents. Our findings provide evidences for the ability of thymol in altering the firing mode of central neurons of snail, which apparently involves the inhibition of calcium and potassium currents. These results further support the interaction of thymol with ion channels and emphasize on the vulnerability of nervous system to this compound.
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Khani S, Abbasi S, Keyhanfar F, Amani A. Use of artificial neural networks for analysis of the factors affecting particle size in mebudipine nanoemulsion. J Biomol Struct Dyn 2018; 37:3162-3167. [PMID: 30238824 DOI: 10.1080/07391102.2018.1510341] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
In this study, a nanoemulsion containing mebudipine [composed of ethyl oleate (oil phase), Tween 80 (T80), Span 80 (S80) (surfactants), polyethylene glycol 400, ethanol (cosurfactants), and deionized water] was prepared with the aim of improving its bioavailability for an effective antihypertensive therapy. Particle size of the formulation was measured by dynamic light scattering. Then, artificial neural networks were used in identifying factors that influence the particle size of the nanoemulsion. Three variables, namely, amount of surfactant system (T80 + S80), amount of polyethylene glycol, and amount of ethanol as cosurfactants, were considered as input values and the particle size was used as output. The developed model showed that all the three inputs had some degrees of effect on particles size: increasing the value of each input decreased the size. Furthermore, amount of surfactant was found to be the dominant factor in controlling the final particle size of nanoemulsion. Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Samira Khani
- a Neuroscience Research Center , Qom University of Medical Sciences , Qom , Iran
| | - Shayan Abbasi
- b Institute of Biochemistry and Biophysics , University of Tehran , Tehran , Iran
| | - Fariborz Keyhanfar
- c Department of Pharmacology , Iran University of Medical Sciences , Tehran , Iran
| | - Amir Amani
- d Department of Medical Nanotechnology, School of Advanced Technologies in Medicine , Tehran University of Medical Sciences , Tehran , Iran.,e Medical Biomaterials Research Center , Tehran University of Medical Sciences , Tehran , Iran
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Vatanparast J, Andalib-Lari F. Camphor elicits epileptiform discharges in snail neurons: The role of ion channels modulation. Neurotoxicology 2017; 60:299-307. [DOI: 10.1016/j.neuro.2015.12.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 12/15/2015] [Accepted: 12/15/2015] [Indexed: 11/25/2022]
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Khani S, Keyhanfar F, Amani A. Design and evaluation of oral nanoemulsion drug delivery system of mebudipine. Drug Deliv 2015; 23:2035-43. [DOI: 10.3109/10717544.2015.1088597] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Bahmaei M, Falahati F, Tayebi L, Mahmoudian M, Farkhondeh T, Kazemi V. Development and Validation of a New HPLC Method for In-Vitro Studies of Mebudipine in Pharmaceutical Formulations. Pharm Chem J 2015. [DOI: 10.1007/s11094-015-1221-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Khani S, Keyhanfar F. Improved oral bioavalability of mebudipine upon administration in PhytoSolve and Phosal-based formulation (PBF). AAPS PharmSciTech 2014; 15:96-102. [PMID: 24151144 DOI: 10.1208/s12249-013-0039-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 10/01/2013] [Indexed: 11/30/2022] Open
Abstract
The aim of this investigation was to examine the efficacy of PhytoSolve and Phosal-based formulation (PBF) to enhance the oral bioavailability of mebudipine, which is a poorly water-soluble calcium channel blocker. The solubility of mebudipine in various oils was determined. PhytoSolve was prepared with a medium-chain triglyceride (MCT) oil (20%), soybean phospholipids (5%), and a 70% fructose solution (75%). The influence of the weight ratio of Phosal 50PG to glycerol in PBF on the mean globule size was studied with dynamic light scattering. The optimized formulation was evaluated for robustness toward dilution, transparency, droplet size, and zeta potential. The in vivo oral absorption of different mebudipine formulations (PhytoSolve, PBF, oily solution, and suspension) were evaluated in rats. The optimized PBF contained Phosal 50PG/glycerol in a 6:4 ratio (w/w). The PBF and PhytoSolve formulations were miscible with water in any ratio and did not demonstrate any phase separation or drug precipitation over 1 month of storage. The mean particle size of PhytoSolve and PBF were 138.5 ± 9.0 and 74.4 ± 2.5 nm, respectively. The in vivo study demonstrated that the oral bioavailability of PhytoSolve and PBF in rats was significantly higher than that of the other formulations. The PhytoSolve and PBF formulations of mebudipine are found to be more bioavailable compared with suspension and oily solutions during an in vivo study in rats. These formulations might be new alternative carriers that increase the oral bioavailability of poorly water-soluble molecules, such as mebudipine.
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Ghasemi Z, Hassanpour-Ezatti M, Kamalinejad M, Janahmadi M. Functional involvement of Ca2+ and Ca2+-activated K+ channels in anethol-induced changes in Ca2+ dependent excitability of F1 neurons in Helix aspersa. Fitoterapia 2011; 82:750-6. [DOI: 10.1016/j.fitote.2011.03.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 03/10/2011] [Accepted: 03/15/2011] [Indexed: 11/16/2022]
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Effect of the two new calcium channel blockers mebudipine and dibudipine on vascular flow of isolated kidney of normal and diabetic rats. PATHOPHYSIOLOGY 2011; 18:175-84. [DOI: 10.1016/j.pathophys.2010.09.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Accepted: 09/06/2010] [Indexed: 11/18/2022] Open
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Sepehr-Ara L, Sepehr-Ara M, Mahmoudian M. Effect of the two new calcium channel blockers mebudipine and dibudipine in comparison to amlodipine on vascular flow of isolated kidney of diabetic rat. ACTA PHYSIOLOGICA HUNGARICA 2010; 97:281-9. [PMID: 20843766 DOI: 10.1556/aphysiol.97.2010.3.4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Calcium channel blockers are clinically useful vasodilators, used widely in the treatment of hypertension. These agents are reported to preserve or improve renal function in patients with essential hypertensive renal disease or diabetic renal disease. Among the classes of calcium channel blockers, dihydropyridine derivatives are widely used because of their potent vasodilating activity and weak cardiodepressant action. Mebudipine and dibudipine are two new 1,4-dihydropyridine calcium channel blockers that recently have been synthesized. In previous research mebudipine and dibudipine showed considerable relaxant effects on vascular and ileal smooth muscle cells. In this study we investigated the effects of these new drugs on vascular flow of isolated kidney of diabetic rat and compare their potencies to amlodipine. It is concluded that mebudipine and dibudipine (1-10 μM) are at least as potent as amlodipine in inhibiting PE-induced perfusion pressure in isolated kidney of diabetic rats. These new dihydropyridines improve kidney perfusion of diabetic rat in the setting of PE infusion. Similarly, amlodipine.
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Affiliation(s)
- L Sepehr-Ara
- Islamic Azad University, Kazeroon Branch, Department of Biology, Kazeroon, Iran.
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Vatanparast J, Janahmadi M. Contribution of apamin-sensitive SK channels to the firing precision but not to the slow afterhyperpolarization and spike frequency adaptation in snail neurons. Brain Res 2008; 1255:57-66. [PMID: 19100724 DOI: 10.1016/j.brainres.2008.12.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Revised: 12/01/2008] [Accepted: 12/02/2008] [Indexed: 10/21/2022]
Abstract
Apamin-sensitive small conductance Ca(2+)-dependent K(+)(SK) channels are generally accepted as responsible for the medium afterhyperpolarization (mAHP) after single or train of action potentials. Here, we examined the functional involvement of these channels in the firing precision, post train AHP and spike frequency adaptation (SFA) in neurons of snail Caucasotachea atrolabiata. Apamin, a selective SK channel antagonist, reduced the duration of single-spike AHP and disrupted the spontaneous rhythmic activity. High frequency trains of evoked action potentials showed a time-dependent decrease in the action potential discharge rate (spike frequency adaptation) and followed by a prominent post stimulus inhibitory period (PSIP) as a marker of slow AHP (sAHP). Neither sAHP nor SFA was attenuated by apamin, suggesting that apamin-sensitive SK channels can strongly affect the rhythmicity, but are probably not involved in the SFA and sAHP. Nifedipine, antagonist of L-type Ca(2+) channels, decreased the firing frequency and neuronal rhythmicity. When PSIP was normalized to the background interspike interval, a suppressing effect of nifedipine on PSIP was also observed. Intracellular iontophoretic injection of BAPTA, a potent Ca(2+) chelator, dramatically suppressed PSIP that confirms the intracellular Ca(2+) dependence of the sAHP, but had no discernable effect on the SFA. During train-evoked activity a reduction in the action potential overshoot and maximum depolarization rate was also observed, along with a decrease in the firing frequency, while the action potential threshold increased, which indicated that Na(+) channels, rather than Ca(2+)-dependent K(+) channels, are involved in the SFA.
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Affiliation(s)
- Jafar Vatanparast
- Department of Biology, College of Sciences, Shiraz University, Adabiat Intersection, Shiraz 71454, Iran.
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Janahmadi M, Farajnia S, Vatanparast J, Abbasipour H, Kamalinejad M. The fruit essential oil of Pimpinella anisum L. (Umblliferae) induces neuronal hyperexcitability in snail partly through attenuation of after-hyperpolarization. JOURNAL OF ETHNOPHARMACOLOGY 2008; 120:360-365. [PMID: 18852037 DOI: 10.1016/j.jep.2008.09.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 08/24/2008] [Accepted: 09/09/2008] [Indexed: 05/26/2023]
Abstract
AIM OF THE STUDY Many biological actions of Pimpinella anisum L. (Ainse), including antiepileptic activity have been demonstrated; however, there is no data concerning its precise cellular mechanisms of action. We determined whether the fruit essential oil of anise affect the bioelectrical activity of snail neurons in control condition or after pentylenetetrazol (PTZ) induced epileptic activity. MATERIALS AND METHODS Intracellular recordings were made under the current clamp condition and the effects of anise oil (0.01% or 0.05%) alone or in combination with PTZ were assessed on the firing pattern, action potential configuration and postspike potentials. RESULTS Anise oil changed the firing pattern from regular tonic discharge to irregular and then to bursting in intact cells or resulted in the robustness of the burst firing and the steepness of the paroxysmal shift induced by PTZ treatment. It also significantly increased the firing frequency and decreased both the after-hyperpolarization potential (AHP) following single action potential and the post-pulse AHP. CONCLUSIONS Likely candidate cellular mechanisms underlying the hyperexcitability produced by anise oil include enhancement of Ca(2+) channels activity or inhibition of voltage and/or Ca(2+) dependent K(+) channels activity underlying AHPs. These finding indicates that a certain caution is needed when Pimpinella anisum is used for treating patients suffering from epilepsy.
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Affiliation(s)
- Mahyar Janahmadi
- Neuroscience Research Center and Department of Physiology, Faculty of Medicine, Shahid Beheshti University (Medical Campus), P.O. Box 19615-1178, Evin, Tehran, Iran.
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50 Hz alternating extremely low frequency magnetic fields affect excitability, firing and action potential shape through interaction with ionic channels in snail neurones. ACTA ACUST UNITED AC 2007. [DOI: 10.1007/s10669-007-9143-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Rouzrokh A, Ebrahimi SA, Rahbr-Roshandel N, Mahmoudian M. Effects of mebudipine and dibudipine, two new calcium channel blockers on voltage-activated calcium currents of PC12 cells. ACTA ACUST UNITED AC 2007; 94:199-207. [PMID: 17853772 DOI: 10.1556/aphysiol.94.2007.3.5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mebudipine and dibudipine are two newly synthesized dihydropyridine (DHP) calcium channel blockers that have been shown to have considerable relaxant effects on vascular and atrial smooth muscle. The in vitro half-lives of mebudipine and dibudipine are reported to be significantly longer than that of nifedipine. In this study, we investigated the effects of mebudipine and dibudipine on voltage-activated Ca2+ channels on differentiated PC12 cells and compared their potencies to amlodipine. Our results point to absence of voltage-activated Ca2+ currents in undifferentiated PC12 cells. It is also concluded that mebudipine and dibudipine, like amlodipine are L-type calcium channel blockers. When tested in a range of 10-100 microM, mebudipine is at least as potent as amlodipine in inhibition of peak Ba2+ currents in differentiated PC12 cells while dibudipine is significantly less potent compared to amlodipine and mebudipine.
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Affiliation(s)
- A Rouzrokh
- Razi Institute for Drug Research, Iran University of Medical Sciences, P.O. Box 14155-6183, Tehran, Iran
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Vatanparast J, Janahmadi M, Asgari AR. The functional consequences of paraoxon exposure in central neurones of land snail, Caucasotachea atrolabiata, are partly mediated through modulation of Ca2+ and Ca2+-activated K+-channels. Comp Biochem Physiol C Toxicol Pharmacol 2006; 143:464-72. [PMID: 16820325 DOI: 10.1016/j.cbpc.2006.04.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2006] [Revised: 04/15/2006] [Accepted: 04/22/2006] [Indexed: 11/25/2022]
Abstract
Toxicity of paraoxon has been attributed to inhibition of cholinesterase, but little is known about its direct action on ionic channels. The effects of paraoxon (0.3 microM-0.6 microM) were studied on the firing behaviour of snail neurones. Paraoxon significantly increased the frequency of spontaneously generated action potentials, shortened the afterhyperpolarization (AHP) and decreased the precision of firing. Short periods of high frequency-evoked trains of action potentials led to an accumulation in the depth and duration of post-train AHPs that was evidenced as an increase in time to resumption of autonomous activity. The delay time in autonomous activity initiation was linearly related to the frequency of spikes in the preceding train and the slope of the curve significantly decreased by paraoxon. The paraoxon induced hyperexcitability and its depressant effect on the AHP and the post-train AHP were not blocked by atropine and hexamethonium. Calcium spikes were elicited in a Na+ free Ringer containing voltage dependent potassium channel blockers. Paraoxon significantly decreased the duration of calcium spikes and following AHP and increased the frequency of spikes. These findings suggest that a reduction in calcium influx during action potential may decrease the activation of calcium dependent potassium channels that participate in AHP generation and act as a mechanism of paraoxon induced hyperexcitability.
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Affiliation(s)
- Jafar Vatanparast
- Neuroscience Research Center and Department of Physiology, Faculty of Medicine, Shaheed Beheshti Medical Sciences University, Evin, P.O.Box 19835-181, Tehran, Iran
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Mirkhani H, Dirin M, Youssef-Zayeh I. Mechanism of vasoselective action of mebudipine, a new calcium channel blocker. Vascul Pharmacol 2005; 42:23-9. [PMID: 15664884 DOI: 10.1016/j.vph.2004.12.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2004] [Accepted: 12/09/2004] [Indexed: 10/26/2022]
Abstract
In previous studies, mebudipine, a newly synthesized dihydropyridine calcium channel blocker, showed a considerable vasoselective action. To investigate the mechanism of this property, the pattern of inhibitory action on the KCl-induced contraction in isolated rat aortic rings and the effect of changing resting membrane potential on the potency of this compound were considered. In addition, its chronotropic and inotropic actions were also studied. Mebudipine inhibited KCl-induced contractions. Its inhibitory effect was progressive and needed time to reach maximum. Incubation of the aortic rings in depolarizing physiological solution (high potassium, zero calcium) resulted in the augmentation of mebudipine effect. The potency of mebudipine in inhibiting aortic contractions and its time- and voltage-dependent action were significantly greater than those of nifedipine. In comparison with nifedipine, mebudipine showed a greater negative chronotropic effect, but in the case of negative inotropism, the reverse relation was observed. It is concluded that mebudipine has a greater time- and voltage-dependent inhibitory effect, as compared to nifedipine and this property could explain its prominent vasoselective action. It has also marked negative chronotropic effect and minor negative inotropic action. With regard to the above findings, mebudipine might have a selective and protective calcium channel blocking effect in ischemic regions (ischemia-selectivity), and the potential to be used in cardiovascular diseases without causing harmful effects such as reflex tachycardia and heart failure which have sometimes been seen with the older agents.
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Affiliation(s)
- Hossein Mirkhani
- Department of Pharmacology, School of Medicine, Shiraz University of Medical Sciences, P.O. Box 71345-1649, Shiraz, Iran.
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