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Okada M, Mizuno W, Nakarai R, Matada T, Yamawaki H, Hara Y. Benzodiazepines inhibit the acetylcholine receptor-operated potassium current (IK.ACh) by different mechanisms in guinea-pig atrial myocytes. J Vet Med Sci 2012; 74:879-84. [PMID: 22333515 DOI: 10.1292/jvms.11-0538] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The anticholinergic effects of 7 benzodiazepines, bromazepam, camazepam, chlordiazepoxide, diazepam, lorazepam, medazepam and triazolam, were compared by examining their inhibitory effects on the acetylcholine receptor-operated potassium current (I(K).(ACh)) in guinea-pig atrial myocytes. All of these benzodiazepines (0.3-300 µM) inhibited carbachol (1 µM)-induced I(K).(ACh) in a concentration-dependent manner. The ascending order of IC(50) values for carbachol-induced I(K).(ACh) was as follows; medazepam, diazepam, camazepam, triazolam, bromazepam, lorazepam and chlordiazepoxide (>300 µM). The compounds, except for bromazepam, also inhibited I(K).(ACh) activated by an intracellular loading of 100 µM guanosine 5'-[γ-thio]triphosphate (GTPγS) in a concentration-dependent manner. The ascending order of IC(50) values for GTPγS-activated I(K).(ACh) was as follows; medazepam, diazepam, camazepam, lorazepam, triazolam chlordiazepoxide (>300 µM) and bromazepam (>300 µM). To clarify the molecular mechanism of the inhibition, IC(50) ratio, the ratio of IC(50) for GTPγS-activated I(K).(ACh) to carbachol-induced I(K).(ACh), was calculated. The IC(50) ratio for camazepam, diazepam, lorazepam, medazepam and triazolam was close to unity, while it for chlordiazepoxide could not be calculated. These compounds would act on the GTP binding protein and/or potassium channel to achieve the anticholinergic effects in atrial myocytes. In contrast, since the IC(50) ratio for bromazepam is presumably much higher than unity judging from the IC(50) values (104.0 ± 30.0 µM for carbachol-induced I(K).(ACh) and >300 µM for GTPγS-activated I(K).(ACh), it would act on the muscarinic receptor. In summary, benzodiazepines had the anticholinergic effects on atrial myocytes through inhibiting I(K).(ACh) by different molecular mechanisms.
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Affiliation(s)
- Muneyoshi Okada
- Laboratory of Veterinary Pharmacology, Kitasato University, Towada, Aomori 034-8628, Japan
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Starcevic B, Sicaja M. Dual intoxication with diazepam and amphetamine: This drug interaction probably potentiates myocardial ischemia. Med Hypotheses 2007; 69:377-80. [PMID: 17320309 DOI: 10.1016/j.mehy.2006.12.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Accepted: 12/07/2006] [Indexed: 11/30/2022]
Abstract
Drug-induced myocardial infarction is not a common phenomenon and the underlying mechanism has been related with the coronary artery spasm in the majority of cases. It is mainly related to illicit substances such as cocaine, ecstasy, LSD and amphetamine. According to the findings in the literature, it is most likely that myocardial ischemia due to amphetamine abuse is a result of combined mechanisms which include coronary artery vasospasm, and in lesser extent thrombus formation or direct myocardial toxicity. Diazepam is also usually found as a substance of abuse. Recent findings indicate that diazepam exerts an inhibitory activity on different isoforms of the enzyme cyclic nucleotide phosphodiesterase, which can be found in the heart muscle and also show that diazepam potentate the positive inotropic effect of both noradrenaline and adrenaline, which subsequently leads to increase in myocardial contractility. We propose that dual intoxication with amphetamine and benzodiazepine potentate their effects on cardiac tissue and coronary arteries which results in larger myocardial injury.
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Affiliation(s)
- Boris Starcevic
- Invasive Cardiology Unit, Department of Internal Medicine, University Hospital Dubrava, Av. Gojka Suska 6, 10000 Zagreb, Croatia
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Gesi M, Fornai F, Lenzi P, Ferrucci M, Soldani P, Ruffoli R, Paparelli A. Morphological alterations induced by loud noise in the myocardium: the role of benzodiazepine receptors. Microsc Res Tech 2002; 59:136-46. [PMID: 12373725 DOI: 10.1002/jemt.10186] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Noise represents an environmental stress factor affecting several organs and apparati, including the cardiovascular system. In experimental animals undergoing noise exposure, subcellular myocardial changes have been reported, especially at mitochondrial level; in particular, after 6 hours of exposure only the atrium exhibited significant mitochondrial alterations, whereas after 12 hours as well as subchronic exposure both atrium and ventricle were damaged. The first part of the present article overviews the experimental evidence on effects of noise on the myocardium. In the second part, the review analyzes the role of benzodiazepine receptors and the potential efficacy of benzodiazepine ligands in preventing the mitochondrial damage induced by noise exposure. Drugs acting at both central and peripheral benzodiazepine receptors significantly prevent this damage. Differences in the amount and the duration of the protective effect might depend on variability in the potency and pharmacokinetics of the specific drug. The effects of the combined treatment with selective and non-selective peripheral benzodiazepine ligands on noise stimulation are discussed at biochemical level reviewing studies on the effects of noise exposure on mitochondrial fractions.
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Affiliation(s)
- Marco Gesi
- Department of Human Morphology and Applied Biology, School of Medicine, University of Pisa, 56126 Pisa, Italy.
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Hara Y, Kobayashi H, Ooshiro S, Futamura K, Nishino T, Chugun A, Temma K, Kondo H. Negative inotropic effect of diazepam in isolated guinea pig heart. J Vet Med Sci 2001; 63:135-43. [PMID: 11258448 DOI: 10.1292/jvms.63.135] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The inotropic effect of diazepam, a benzodiazepine derivative, and its mechanism of action were examined using guinea pig heart and single ventricular cell preparations. In Langendorff hearts and right ventricular free-wall preparations, diazepam (10 to 100 microM) produced a monophasic negative inotropic effect in a concentration dependent manner. Neither a central type (flumazenil 1 microM) nor a peripheral type (PK11195 10 microM) of benzodiazepine receptor antagonist antagonized the monophasic negative inotropic effects of diazepam. Diazepam (10 to 100 microM) shortened action potential duration of papillary muscle in a concentration dependent manner. In isolated single ventricular cells, diazepam (30 and 100 microM) inhibited the calcium current (I(Ca)) in a concentration dependent manner. Diazepam produced a significant decrease in I(Ca) elicited by first depolarizing pulses, however, the decrease of I(Ca) was not augmented during a train of depolarizing pulses. Thus, diazepam appears to produce a tonic block of cardiac calcium channels and the mode of inhibition is clearly different from the use-dependent block of verapamil. From these results, it was concluded that diazepam produces a monophasic negative inotropic effect that is independent of the benzodiazepine receptor, and is probably mediated through an inhibition of I(Ca) in guinea pig heart preparations.
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Affiliation(s)
- Y Hara
- Department of Veterinary Pharmacology, School of Veterinary Medicine and Animal Sciences, Kitasato University, Aomori, Japan
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Gesi M, Riva A, Soldani P, Fornai F, Natale G, Lenzi P, Pellegrini A, Paparelli A. Central and peripheral benzodiazepine ligands prevent mitochondrial damage induced by noise exposure in the rat myocardium: an ultrastructural study. THE ANATOMICAL RECORD 1999; 255:334-41. [PMID: 10411400 DOI: 10.1002/(sici)1097-0185(19990701)255:3<334::aid-ar9>3.0.co;2-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Noise represents an environmental stress factor affecting several organs and apparatuses, including the cardiovascular system. In experimental animals undergoing noise exposure, subcellular myocardial changes have been reported, especially at the mitochondrial level. In previous studies we found that diazepam, acting at both central and peripheral benzodiazepine receptors, prevented the onset of this myocardial damage. In the present study, we investigated the specific role played by central and/or peripheral benzodiazepine receptors in preventing noise-induced myocardial alterations. In particular, the effect of clonazepam as a selective ligand for central sites, in comparison with the efficacy of ligands selective for peripheral sites, such as Ro 5-4864 and PK-11195, was evaluated. Rats were pretreated with the test drugs 30 min before exposure to noise for 6 or 12 hr and then sacrificed. After fixing, samples of right atrium and ventricle were taken and processed for either transmission or scanning electron microscopy. After 6 hr of noise exposure, only the atrium exhibited significant mitochondrial alterations, whereas after 12 hr both atrium and ventricle were damaged. As expected, diazepam prevented noise-induced mitochondrial injury at both 6 and 12 hr. By contrast, clonazepam was effective only after 6 hr. The peripheral ligand PK-11195 attenuated mitochondrial damage at both 6 and 12 hr, whereas Ro 5-4864 was effective only after 12 hr. In the present study, we confirm that noise exposure induces mitochondrial damage in the rat myocardium. Drugs acting at both central and peripheral benzodiazepine receptors significantly prevent this damage. Differences in the amount and in the duration of the protective effect might depend on variability in the potency and in the pharmacokinetics of the specific drugs.
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Affiliation(s)
- M Gesi
- Department of Human Morphology and Applied Biology, Faculty of Medicine, University of Pisa, Italy.
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Zeegers A, van Wilgenburg H, Leeuwin RS. Cardiac effects of benzodiazepine receptor agonists and antagonists in the isolated rat heart: a comparative study. Life Sci 1999; 63:1439-56. [PMID: 9952290 DOI: 10.1016/s0024-3205(98)00411-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Effects of PK 11195 and flumazenil on cardiac responses to diazepam, clonazepam and zolpidem were compared. Coronary flow rate was increased at relatively low doses of diazepam and decreased at higher doses. Clonazepam induced a dose-dependent increase, and zolpidem a decrease of coronary flow rate. PK 11195 reduced the diazepam-induced increase of coronary flow rate, and flumazenil was ineffective. Neither antagonist evoked substantial changes in the decrease of coronary flow rate. PK 11195, and less so flumazenil, antagonized the clonazepam-induced increase. PK 11195 and flumazenil only in their highest doses suppressed and respectively potentiated the zolpidem-induced decrease. Inotropy showed a biphasic response in the presence of diazepam, i.e. an initial transient decrease, followed by a dose-dependent increase in two steps. Clonazepam induced a similar response. Zolpidem increased the inotropy. The negative inotropic response induced by diazepam did not change significantly in the presence of PK 11195 or flumazenil. The positive inotropic response was suppressed by PK 11195, and less so by flumazenil. The negative response to clonazepam was antagonized by both PK 11195 and flumazenil; the positive response was not significantly changed. In the presence of lower doses of PK 11195, the zolpidem-induced response was potentiated, whereas higher doses produced reversal; flumazenil potentiated the response. In conclusion, the results support earlier suggestions, involving receptor mechanisms with cardiac effects of benzodiazepines. Both agonists and antagonists (inter)act in a different manner, suggesting that rather ambiguous receptor mechanisms are involved in benzodiazepine effects in the heart.
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Affiliation(s)
- A Zeegers
- Department of Pharmacology, University of Amsterdam, Academic Medical Center, The Netherlands
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Hara Y, Chugun A, Futamura K, Nishino T, Kondo H. Diazepam Increases Calcium Sensitivity of the Skinned Cardiac Muscle Fiber in Guinea Pig. ACTA ACUST UNITED AC 1999. [DOI: 10.1016/s0021-5198(19)30818-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Hara Y, Kaigo H, Minami I, Watanabe H, Gomi H, Nishimura H, Chugun A, Kondo H. Diazepam potentiates the positive inotropic effects of histamine and forskolin in guinea-pig papillary muscles. J Vet Pharmacol Ther 1998; 21:375-9. [PMID: 9811438 DOI: 10.1046/j.1365-2885.1998.00160.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
There have been diverse reports on the effects of diazepam on cardiac contractility. The purpose of this study was to examine whether diazepam modifies the inotropic response elicited by histamine on an isolated guinea-pig papillary muscle. The responses of electrically driven papillary muscle to histamine and cyclic AMP-related inotropic agents were recorded in the absence and in the presence of diazepam. Histamine and forskolin, which directly stimulate adenylate cyclase, significantly increased the contractile force in the papillary muscle in a concentration-dependent manner. A histaminergic H2-receptor antagonist, cimetidine, but not a H1-receptor antagonist, diphenhydramine, at 10 microM produced a rightward shift in the concentration-response curve for histamine. Diazepam (10 microM) shifted the concentration-response curve for histamine and forskolin to the left by 1.8 and 1.6 times, respectively. Neither a central type (fulmazenil) nor a peripheral type (PK11195) of benzodiazepine receptor antagonist modified the effect of diazepam on the histaminergic-evoked contraction. Phosphodiesterase blockade by 3-isobutyl-1-methylxanthine shifted the concentration-dependent curve for histamine to the left. A combination of 3-isobutyl-1-methylxanthine also produced a leftward shift of the curve. However, there was no significant difference between the 3-isobutyl-1-methylxanthine only group and the combination group. These results indicate that diazepam potentiates the positive inotropic effect produced by histamine, probably mediated via an increase in cyclic AMP levels induced by histamine.
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Affiliation(s)
- Y Hara
- Department of Veterinary Pharmacology, School of Veterinary Medicine and Animal Sciences, Kitasato University, Aomori, Japan
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Leeuwin RS, Zeegers A, van Hamme J, van Wilgenburg H. Modification of cardiac actions of RO 05-4864 by PK 11195 and flumazenil in the perfused rat heart. Life Sci 1997; 61:1631-42. [PMID: 9363978 DOI: 10.1016/s0024-3205(97)00768-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The benzodiazepine analogue Ro 05-4864 [chlorodiazepam] (2.10[-5] to 4.10[-4] M) induced a concentration-dependent increase of coronary flow rate (Emax 82.4% [+/- 2.2 SEM]) and an increase of contraction force (Emax 68.3% [+/- 4.7 SEM]) of the retrograde perfused, isolated Langendorff rat heart. The influence of PK 11195, antagonist of the peripheral type benzodiazepine receptor, and flumazenil (Anexate), antagonist of the central type benzodiazepine receptor, on these responses to Ro 5-4864 was studied. In concentrations of 10(-7) to 5.10(-5) M, PK 11195 significantly reduced both the increase of coronary flow rate and of contraction force, without affecting these functions by itself; the positive inotropic response produced by Ro 05-4864 was even abolished in the presence of 5.10(-5) M PK 11195. The Emax values of Ro 05-4864 on both coronary flow and inotropy were reduced significantly by PK 11195. In the presence of flumazenil, 10(-7) to 10(-5) M, both the vasodilatory and the positive inotropic response induced by Ro 05-4864 were significantly counteracted as well. The Emax values of Ro 05-4864 were reduced significantly. In conclusion, the results support earlier suggestions that it is tempting to involve peripheral type benzodiazepine receptors in cardiac actions of benzodiazepines. The finding that the centrally acting benzodiazepine antagonist flumazenil reduced the cardiac actions of Ro 05-4864 is as yet difficult to explain. On the other hand concentrations of both agonist and antagonist employed are so-much high that interference of other receptors than benzodiazepine receptors must be considered as well.
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Affiliation(s)
- R S Leeuwin
- Department of Pharmacology, University of Amsterdam, Academic Medical Centre, The Netherlands.
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Leeuwin RS, Zeegers A, Van Wilgenburg H. Flunarizine but not theophylline modulates inotropic responses of the isolated rat heart to diazepam. Eur J Pharmacol 1996; 315:153-7. [PMID: 8960878 DOI: 10.1016/s0014-2999(96)00603-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Diazepam (2 x 10(-5)-6 x 10(-4) M) induced a concentration-dependent positive inotropic effect on the perfused rat heart which was preceded by a transient concentration-dependent negative inotropic response. The influence of the Ca(2+)-entry blocking drug, flunarizine, and the adenosine receptor blocking drug, theophylline on these inotropic responses was studied. Flunarizine in concentrations of 10(-9)-10(-6) M antagonized the positive inotropic response to diazepam significantly; the negative inotropic response was reduced as well. At the lower concentrations of diazepam the negative inotropic response was completely abolished in the presence of flunarizine. The actions of the Ca(2+)-entry blocker were related to the concentrations used. Theophylline in concentrations up to 5 x 10(-5) M did not interfere with either inotropic response to diazepam. The results suggest that Ca2+ currents in the myocardium are involved with the response of the isolated heart to diazepam. It is concluded that the finding that the negative inotropic effect of diazepam was almost abolished by flunarizine suggests that the site of this response most be associated with Ca(2+)-current mechanisms.
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Affiliation(s)
- R S Leeuwin
- Department of Pharmacology, University of Amsterdam, The Netherlands
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Serrano JS, Jiménez CM, Serrano MI, Balboa B. A possible interaction of potential clinical interest between digoxin and acarbose. Clin Pharmacol Ther 1996; 60:589-92. [PMID: 8941033 DOI: 10.1016/s0009-9236(96)90156-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This case report describes a 69-year-old woman with diabetes mellitus and heart failure who repeatedly had unusual subtherapeutic levels of plasma digoxin. When the drug therapeutic regimen was checked it was found that a new drug, acarbose, had been added to the therapeutic regimen before the unexpected laboratory reported results. Because other drugs included in her therapeutic menu were rejected as being responsible for decreased levels of digoxin, it was recommended to discontinue acarbose to evaluate its role. In the absence of acarbose, the plasma concentration of digoxin increased to the therapeutic range. We concluded that acarbose may be responsible for a pharmacokinetic interaction with digoxin by a still unknown mechanism. Although discontinuation of acarbose was recommended, the attending physician discontinued administration of digoxin because the clinical condition of the patient did not get worse during subtherapeutic levels of digoxin.
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Affiliation(s)
- J S Serrano
- Clinical Pharmacology Unit, University Hospital Macarena, Spain
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Martinez E, Peñafiel R, Collado MC, Hernández J. Diazepam potentiates the positive inotropic effect of isoprenaline in rat ventricle strips: role of cyclic AMP. Eur J Pharmacol 1995; 282:169-75. [PMID: 7498272 DOI: 10.1016/0014-2999(95)00325-f] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The responses of the electrically driven right ventricle strip of the rat heart to isoprenaline and other cyclic AMP-related inotropic agents were recorded in the absence and in the presence of diazepam. Isoprenaline, in concentrations ranging from 10 nM to 1 microM, significantly increased, in a concentration-dependent manner, the contractile force in this preparation. Diazepam (10 microM) produced a leftward shift in the isoprenaline concentration-response curve and significantly reduced its EC50. Higher concentrations of diazepam (100 microM) produced no further shift, but reduced the maximum of the concentration-response curve of isoprenaline. Forskolin (0.5-10 microM), which directly stimulates adenyl cyclase, also produced a concentration-dependent increase in cardiac contractility. Diazepam (10 microM) displaced to the left the concentration-response curve for forskolin and reduced its EC50. The cyclic AMP analogous dibutyryl cyclic AMP (0.1-1 mM) produced concentration-dependent positive inotropic effects which were not significantly modified in the presence of diazepam (10 microM). Diazepam (10 microM) significantly enhanced the cyclic AMP production induced by isoprenaline (0.1 microM) and forskolin (10 microM) by about 136% and 35% respectively. These results indicate that diazepam potentiates the positive inotropic effect induced by beta-adrenoceptor agonists, probably by increasing cyclic AMP production induced by these agents.
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Affiliation(s)
- E Martinez
- Department of Pharmacology, Medical School, Murcia, Spain
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POSTER COMMUNICATIONS. Br J Pharmacol 1995. [DOI: 10.1111/j.1476-5381.1995.tb16307.x] [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] Open
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Abstract
The effect of diazepam on cardiac contractility was investigated in electrically-driven right ventricular strips of the rat. Diazepam produced a concentration-dependent negative inotropic effect which was antagonized by either flumazenil, a benzodiazepine central-type receptor antagonist, or PK 11195, a benzodiazepine peripheral type receptor antagonist. The results suggest that the inhibitory effect of diazepam on cardiac contractility in the rat is mediated by both central and peripheral benzodiazepine receptors.
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Affiliation(s)
- J Hernández
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Espinardo-Murcia, Spain
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Gonzalez R, Zeegers A, Eigenhuis J, Leevwin R, van Wilgenburg H. A comparative study of diazepam and midazoiam induced actions in isolated rat hearts. Eur J Pharmacol 1990. [DOI: 10.1016/0014-2999(90)93593-f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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