Flunarizine but not theophylline modulates inotropic responses of the isolated rat heart to diazepam

The effects of N-acetylcysteine on cisplatin-induced changes of cardiodynamic parameters within coronary autoregulation range in isolated rat hearts

The aim of this study was to evaluate the effects of chronic NAC administration along with cisplatin on cisplatin-induced cardiotoxicity by means of coronary flow (CF), cardiodynamic parameters, oxidative stress markers and morphological changes in isolated rat heart. Isolated hearts of Wistar albino rats (divided into four groups: control, cisplatin, NAC and cisplatin+NAC group) were perfused according to Langendorff technique at constant coronary perfusion pressure starting at 50 and gradually increased to 65, 80, 95 and 110 cm H2O to evaluate cardiodynamic parameters within autoregulation range. Samples of coronary venous effluent (CVE) were collected for determination of CF and biochemical assays, and heart tissue samples for biochemical assays and histopathological examination. Cisplatin treatment decreased CF and heart rate, and increased left ventricular systolic pressure and maximum left ventricular pressure development rate. Cisplatin increased H2O2 and TBARS, but decreased NO2(-) levels in CVE. In tissue samples, cisplatin reduced pathological alterations in myocardium and coronary vessels, with no changes in the amount of total glutathione, as well as in activity of glutathione peroxidase and glutathione reductase. NAC coadministration, by reducing oxidative damage, attenuated cisplatin-induced changes of cardiodynamic and oxidative stress parameters, as well as morphological changes in myocardium and coronary vasculature.

Morphological alterations induced by loud noise in the myocardium: the role of benzodiazepine receptors

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.

Negative inotropic effect of diazepam in isolated guinea pig heart

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.

Central and peripheral benzodiazepine ligands prevent mitochondrial damage induced by noise exposure in the rat myocardium: an ultrastructural study

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.