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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The electrophysiological and antiarrhythmic effects of pirmenol HCl were examined using the microelectrode technique applied to multicellular preparations and the suction-pipette whole-cell clamp method applied to ventricular myocytes from rabbit and guinea pig hearts. Pirmenol at 5 microM and higher doses suppressed the sinus node automaticity by depressing the slow diastolic depolarization without changing the maximum diastolic potential. Pirmenol at 1 microM and higher doses depressed the maximum upstroke velocity (Vmax) of action potentials and prolonged the action potential duration at 90% repolarization in atrial muscles and Purkinje fibers without affecting resting membrane potentials. Pirmenol at 5 microM depressed the early part of the plateau and lengthened the final repolarization of the action potentials in ventricular myocytes, of which effects were attributed to the depression of the calcium current and the delayed outward K+ current. Triggered tachyarrhythmias arising from delayed afterdepolarizations in papillary muscles and ventricular myocytes were markedly inhibited by 1-5 microM pirmenol. The drug changed the amplitude and appearance of the transient inward current in ventricular myocytes. These results suggest that pirmenol has electrophysiologic properties that could provide an antiarrhythmic action on various types of arrhythmias.
J Cardiovasc Pharmacol 1990 Dec
PMID:Electrophysiologic and antiarrhythmic actions of pirmenol on rabbit and guinea pig cardiac preparations. 170 93

The purpose of this study was to evaluate the cardiac electrophysiological effects of McN-5691, a new calcium-channel blocking antihypertensive drug. In anesthetized dogs, the primary electrophysiological effect of McN-5691 was dose-related prolongation of AV-nodal conduction time and refractoriness (0.1-1.0 mg/kg i.v.), which correlated with McN-5691 plasma levels. There were no significant effects on atrial or ventricular conduction times, QTc, or ventricular monophasic action potential duration. This profile was similar to that of verapamil. McN-5691 caused concentration-related, rate-dependent reductions in Vmax and amplitude of slow-response action potentials in guinea pig papillary muscle: ED-20% for depression of Vmax was 0.72 +/- 0.32 microM. Verapamil was more potent in depressing these action potentials: ED-20% for depression of Vmax was 0.03 +/- 0.01 microM. McN-5691 also caused rate-dependent reduction in Vmax and amplitude of canine Purkinje fiber action potentials, but only at relatively high concentrations: ED-20% for depression of Vmax was 55 +/- 12 microM. McN-5691 also reduced the action potential duration (0.3-30 microM) without affecting the slope of phase 4 depolarization and the maximum diastolic potential. Verapamil also reduced Vmax in Purkinje fibers (ED-20% for depression of Vmax was 32 +/- 3 microM) and shortened the action potential duration. The results show that McN-5691 has cardiac electrophysiological effects consistent with blockade of the slow inward calcium current, and that this activity occurs at concentrations well below those having local anesthetic activity. In addition, its lower potency in comparison to verapamil in depressing slow responses suggests a lesser propensity for negative inotropic effects.
J Cardiovasc Pharmacol 1990 Oct
PMID:Cardiac electrophysiologic effects of McN-5691, a new calcium-channel blocking antihypertensive agent. 170 95

The rate-dependent electrophysiological effects of sotalol (30 microM), mexiletine (10 and 18 microM), and their coadministration were examined in isolated dog cardiac Purkinje fibers following abrupt changes in pacing cycle length. Combination of 30 microM sotalol with 10 microM mexiletine significantly lengthened premature action potential durations at diastolic intervals of less than 50 ms while the basic action potential duration evoked at a stimulus frequency of 2 Hz was not affected. This effect on the premature action potential duration was attenuated when the higher mexiletine concentration (18 microM) was coadministered with sotalol. The fast time constant for restitution of the action potential duration was significantly slowed by either combination. Coadministration of sotalol and mexiletine, like mexiletine alone, produced a rate-dependent depression of Vmax that displayed a second slow time component during recovery. This slow component for recovery of Vmax was not distinguished in the absence of drug or in the presence of sotalol alone. Sotalol-induced lengthening of the action potential duration observed at slow pacing frequencies was also attenuated by addition of mexiletine; and, under these conditions, Purkinje fiber early afterdepolarizations were prevented. In addition, the range of premature action potential durations was significantly decreased by mexiletine and by the combination, while sotalol alone increased this range slightly. These results indicate that coadministration of sotalol and mexiletine may provide beneficial electrophysiological effects expected to provide enhanced antiarrhythmic efficacy and fewer proarrhythmic complications in patients.
J Cardiovasc Pharmacol 1990 Oct
PMID:Sotalol and mexiletine: combination of rate-dependent electrophysiological effects. 170 96

The effects of verapamil and nifedipine on cellular mechanisms of arrhythmia were examined in isolated canine Purkinje fiber-papillary muscles. Microelectrode recordings were made simultaneously from both tissues. Preparations were superfused with Tyrode's solution modified to mimic specific conditions of ischemia for 40 min with or without calcium channel blockers. Verapamil or nifedipine resulted in significantly greater depolarization of Purkinje tissue in response to ischemic conditions and increased the incidence of inexcitability or conduction block in Purkinje and muscle tissues. These calcium channel blockers caused only minor changes in ischemia-induced depolarization of muscle. In Purkinje tissue, return to nonischemic conditions in the absence of drugs caused, in sequence, oscillatory afterpotentials, temporary depolarization to inexcitability, and a phase of automaticity at low membrane potential. These events did not occur in muscle. Verapamil or nifedipine abolished oscillatory afterpotentials and low membrane potential automaticity in Purkinje tissue. However, reperfusion-induced depolarization and inexcitability of Purkinje tissue was delayed but not attenuated. This study demonstrates that verapamil or nifedipine exacerbate depolarization and depression of conduction in Purkinje tissue exposed to ischemic conditions. However, verapamil and nifedipine suppress some but not all potential mechanisms of arrhythmia induced by reperfusion.
J Cardiovasc Pharmacol 1991 Jan
PMID:Effects of verapamil and nifedipine on mechanisms of arrhythmia in an in vitro model of ischemia and reperfusion. 170 59

The antiischemic efficacy of the converting enzyme inhibitor (CEI) benazepril was investigated in a randomized, placebo-controlled double-blind study with intraindividual crossover in 11 normotensive patients with angiographically proven coronary artery disease. Bicycle ergometry and 24-h ambulatory ECG were performed before and after 2-week treatment with placebo and benazepril, respectively. Plasma concentrations of atrial natriuretic peptide (ANP) and plasma renin activity (PRA) were measured before each exercise test. Maximal exercise-induced ST-segment depression was not significantly influenced by benazepril therapy (placebo 2.09 +/- 1.22 mm, benazepril 1.91 +/- 1.00 mm). Systolic blood pressure/heart rate (SBP/HR) product at maximum workload remained almost constant with 253 +/- 43 with placebo and 253 +/- 39 with benazepril treatment. The number of anginal attacks and ischemic episodes detected by ambulatory ECG were not significantly reduced. PRA increased significantly from 2.18 +/- 3.76 to 9.62 +/- 8.49 ng/ml/h after benazepril (p less than 0.005), whereas plasma concentrations of ANP remained unchanged (28.04 +/- 12.39 vs. 26.73 +/- 11.09 pg/ml). Therefore, measurement of ST-segment depression with exercise in 11 normotensive patients with coronary artery disease produced no evidence of an antiischemic action for the CEI benazepril 10 mg twice daily (b.i.d.) for 2 weeks, but an improvement was observed in six patients.
J Cardiovasc Pharmacol 1991 May
PMID:Converting enzyme inhibition in coronary artery disease: a randomized, placebo-controlled trial with benazepril. 171 85

The presence of sulfhydryl (SH) groups appears to be fundamental to nitrate-induced vasodilation and N-acetylcysteine (NAC), a sulfhydryl (SH)-donor substance, potentiates hemodynamic responsiveness to nitrates. We investigated the effect of simultaneous administration of NAC and isosorbide dinitrate (ISDN) on development of nitrate tolerance. In a double-blind, randomized, placebo-controlled cross-over study, seven patients with stable angina pectoris were treated for two 8-day periods with ISDN (40 mg four times daily, q.i.d.) together with NAC (controlled release 600 mg q.i.d.) or matching placebo. Bicycle exercise tests were performed before treatment was started, 1 h after treatment was started, and at day 8. After 8-day treatment with ISDN + placebo, responses determined by exercise testing were diminished as compared with responses obtained during acute therapy and did not differ from baseline values, suggesting development of tolerance to ISDN. During treatment with ISDN + NAC, time to 1-mm ST depression was significantly prolonged (441 +/- 44 vs. 381 +/- 40 s, mean +/- SEM) and total ST segment depression significantly reduced (1.9 +/- 0.7 vs. 3.5 +/- 0.8 mm) as compared with baseline values. The reduction in ST segment depression was significantly more pronounced during ISDN + NAC (46%) as compared with ISDN + placebo (23%). Although exercise time and time to angina pectoris were unaffected. NAC augmented the antiischemic effects of ISDN as assessed by ECG. This finding may suggest that development of nitrate tolerance is modified by chronic oral high-dose NAC administration.
J Cardiovasc Pharmacol 1991 Jun
PMID:Continuous oral N-acetylcysteine treatment and development of nitrate tolerance in patients with stable angina pectoris. 171 11

The cardiovascular effects of the phenyldihydropyridine derivative elgodipine (0.3, 1, 3, 10, and 30 microgram/kg/min) were studied in normal conscious pigs and in pigs with chronic left ventricular dysfunction (LVD, caused by coronary artery occlusion) without and after beta-adrenoceptor blockade with propranolol (0.5 mg/kg + 0.5 mg/kg/h). In normal pigs, elgodipine increased cardiac output from 2.57 +/- 0.09 to 5.21 +/- 0.24 L/min (p less than 0.05) as a result of a doubling of the heart rate. Mean arterial blood pressure decreased from 94 +/- 2 to 76 +/- 3 mm Hg (p less than 0.05) as a result of a decrease in systemic vascular resistance. Left ventricular (LV) dP/dtmax increased (by up to 78 +/- 9%), but left ventricular end-diastolic pressure (LVEDP) remained unchanged. After propranolol administration elgodipine did not increase LV dP/dtmax, and the increase in heart rate was attenuated, resulting in a smaller increase in cardiac output (from 2.11 +/- 0.13 to 3.09 +/- 0.23 L/min, p less than 0.05), but an unchanged vasodilator response. In pigs with LVD, elgodipine increased cardiac output and LV dP/dtmax less than in normal animals, but the vasodilator response was not affected. LVEDP decreased from 14.6 +/- 1.6 to 11.7 +/- 2.5 mm Hg (p less than 0.05). In animals with LVD, propranolol caused a more severe depression of systemic hemodynamics, but did not modify the cardiovascular responses to elgodipine. Its cardiovascular profile suggests that elgodipine may not only be useful in the treatment of cardiovascular disorders for which other dihydropyridines are already in use, but also in mild chronic heart failure.
J Cardiovasc Pharmacol 1991 Jun
PMID:Cardiovascular effects of elgodipine in conscious pigs with a normal coronary circulation and in conscious pigs with a healed myocardial infarction. 171 24

Patients with left ventricular hypertrophy (LVH) often exhibit manifestations of myocardial ischemia. In 17 hypertensive patients (group 1, mean age of 56 +/- 4 years, 10 females, 7 males) with ST-segment depression during the exercise electrocardiogram (ECG) and effort angina and normal coronary arteriograms, the left ventricular function at rest and during exercise was studied by heart catheterization. The results were compared with 17 hypertensive patients (group 2, mean age of 56 +/- 6 years, 6 females, 11 males) with coronary artery disease (CAD). The normal pulmonary wedge pressure at rest (group 1, 8.9 +/- 3 mm Hg; group 2, 8.9 +/- 3 mm Hg) was pathologically increased (p less than 0.001) in both groups (group 1, 27.1 +/- 5 mm Hg; group 2, 28.8 +/- 7 mm Hg) even at a work load of 50 W with a further increase at 75 W to 31 +/- 4 and 29.7 +/- 4 mm Hg, respectively. Cardiac output was normal. There was no significant correlation between ST-segment depression, pulmonary wedge pressure, LVH, and Holter ECG. Hypertensive patients without CAD may reveal a disturbed pump function due to ischemia even at low work loads, which does not differ significantly from patients with CAD. This may provoke subendocardial fibrosis and thereby contribute to the development of heart failure.
J Cardiovasc Pharmacol 1991
PMID:Impaired left ventricular function during exercise in hypertensive patients with normal coronary arteriograms. 171 61

Standard microelectrode methods were used to record intracellular action potentials from strips of guinea pig right ventricular myocardium superfused with either standard physiological saline (pH 7.3; PO2 greater than 650 mm Hg; [K+] = 5.6 mM) or the same solution modified to produce either hyperkalemia ([ K+] = 11.2 mM), acidosis (pH = 6.3), or hypoxia (PO2 = 60 mm Hg). The effects on action potential parameters of three therapeutic concentration of lidocaine, flecainide, and encainide were studied under all four conditions at four different drive rates (interstimulus interval = 2,400, 1,200, 600, and 300 ms). Hyperkalemia in the absence of drugs produced reductions in resting potential (-87.9 +/- 3.8 to -74.6 +/- 3.3 mV), maximum rate of depolarization (316 +/- 68 to 240 +/- 12 V/s), and action potential duration (178 +/- 21 to 165 +/- 27 ms). All three drugs produced increased depression of Vmax in hyperkalemia compared to control conditions but, at all three concentrations and all four rates, this enhancement of effect was greater for lidocaine than for either of the other two agents (which did not differ significantly from each other; p less than 0.001). Similar though less marked effects were produced by acidosis (3.5 mV depolarization and 19% reduction in Vmax), and once again the depression of Vmax by lidocaine was enhanced more by this intervention than were the actions of encainide or flecainide (p less than 0.01). Hypoxia had no effect on action potential parameters other than duration and no significant modulation of drug actions was seen for this intervention.(ABSTRACT TRUNCATED AT 250 WORDS)
J Cardiovasc Pharmacol 1991 Jul
PMID:Effects of hyperkalemia, acidosis, and hypoxia on the depression of maximum rate of depolarization by class I antiarrhythmic drugs in guinea pig myocardium: differential actions of class Ib and Ic agents. 171 92

In this study, the effect of bradykinin on coronary flow in the isolated rat heart was significantly potentiated when cysteine or the sulfhydryl-containing converting enzyme inhibitors captopril and zofenoprilat were administered simultaneously. In contrast, the effect of concomitant administration of enalaprilat only slightly increased the effect of bradykinin on coronary flow. In nitrate-tolerant hearts of rats pretreated with isosorbide dinitrate (15 mg daily), the increase in coronary flow by nitroglycerin and bradykinin was significantly less when compared to control hearts. The effect of captopril was not affected by pretreatment. The involvement of endothelium-derived relaxing factor (EDRF) in the effect of captopril was apparent from experiments with L-arginine, the precursor of EDRF, and L-NMMA, the "false" precursor of EDRF. L-Arginine increased the effect of captopril, whereas L-NMMA showed a competitive antagonism for the effect of captopril on coronary flow in the isolated rat heart. Clinically, the effect of captopril was studied in 10 patients with stable, exercise-induced angina pectoris that had been treated for 3 weeks with slow-release isosorbide dinitrate (20 mg four times daily). At day 7, a baseline exercise test was obtained. Subsequently, patients with chest pain and at least 1-mm ST-segment depression on the ECG during exercise were included. They received on day 14 and 21 either captopril (25 mg) or placebo 1 h before exercise testing in a randomized, double-blind, crossover design. Captopril significantly improved the combined score of maximal ST-segment depression, maximal workload, and time to angina when compared to placebo. No differences in the pressure-rate index at rest and during exercise were seen. These results indicate that the sulfhydryl group of certain angiotensin converting enzyme inhibitors can potentiate their effect on the endogenous nitrovasodilator EDRF. In the clinical situation, this may lead to an improved exercise performance in patients with stable angina pectoris during chronic nitrate treatment, independent of its systemic vascular effects.
J Cardiovasc Pharmacol 1991 Sep
PMID:Converting enzyme inhibitors and the role of the sulfhydryl group in the potentiation of exo- and endogenous nitrovasodilators. 172 Aug 43


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