The Experts below are selected from a list of 5547 Experts worldwide ranked by ideXlab platform
Wilson S Colucci - One of the best experts on this subject based on the ideXlab platform.
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effects of myocardial Alpha 1 Adrenergic receptor stimulation and blockade on contractility in humans
Circulation, 1991Co-Authors: J S Landzberg, J D Parker, D F Gauthier, Wilson S ColucciAbstract:BACKGROUNDAlthough Alpha-Adrenergic Receptors are present in both normal and failing human left ventricular myocardium and mediate a positive inotropic effect in several other species, it is not known whether stimulation of myocardial Alpha-Adrenergic Receptors exerts a positive inotropic effect or contributes to basal contractile state in vivo in humans.METHODS AND RESULTSWe studied 15 patients with angiographically normal coronary arteries (seven with normal left ventricular function and eight with left ventricular failure). To avoid the confounding effects of changes in ventricular loading conditions and systemic reflex mechanisms, the Alpha-Adrenergic receptor-selective antagonist phentolamine and agonist phenylephrine were infused directly into the left main coronary artery, and the change in contractile state was assessed by measuring left ventricular peak (+)dP/dt. Phentolamine alone had no effect on left ventricular contractility. Phenylephrine exerted a concentration-related positive inotropic ef...
R Michael M D Rosen - One of the best experts on this subject based on the ideXlab platform.
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developmental changes in modulation of cardiac repolarization by sympathetic stimulation the role of beta and Alpha Adrenergic Receptors
Journal of Cardiovascular Electrophysiology, 1997Co-Authors: Mark Cua, Alexei Shvilkin, Peter Danilo, R Michael M D RosenAbstract:Sympathetic Modulation of Cardiac Repolarization. Introduction: Our goals were to study the role of development in determining the cardiac effects of sympathetic neural activation, and to identify the roles of α- and β-Adrenergic receptor-mediated pathways in modulating the effects of sympathetic stimulation. Methods and Results: We compared responses of young and adult canine hearts in situ to right, left, and bilateral stellate ganglion stimulation. We focused on changes in heart rate, rhythm, QT interval, rate-corrected QT interval (QT), and T wave amplitude. Right stellate stimulation (RSS) induced more pronounced sinus tachycardia in adult than young animals. Left stellate stimulation (LSS) Induced junctional tachycardia in adult more than young animals. In adults, LSS and RSS prolonged QTc (LSS > RSS). whereas 1-week-olds manifested QTc shortening with RSS. LSS also increased T wave amplitude, most markedly in adults. In all studies, bilateral stellate stimulation induced responses intermediate between those seen with RSS and LSS. β-Adrenergic blockade (propranolol) aholished all responses to LSS in adult hearts, but α-blockade (prazosin) attenuated only the LSS-induced prolongation in QTc. Conclusion: In the postnatal modulation of cardiac rhythm, rate, and repolarization by the sympathetic nervous system, β-Adrenergic Receptors play a major role at all ages, whereas α-Adrenergic Receptors play a lesser role, which is manifested only in adults. Moreover, expression of junctional tachycardias, which are β-Adrenergically modulated, is seen only in the adults.
Marvin L. Bayne - One of the best experts on this subject based on the ideXlab platform.
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Cloning, expression and characterization of human Alpha Adrenergic Receptors Alpha 1a, Alpha 1b and Alpha 1c.
Biochemical and biophysical research communications, 1994Co-Authors: David H. Weinberg, Prashant Trivedi, Carina P. Tan, Sudha W. Mitra, A. Perkins-barrow, D. Borkowski, Catherine D. Strader, Marvin L. BayneAbstract:The three human Alpha Adrenergic receptor subtypes, Alpha 1a, Alpha 1b, and Alpha 1c, have been cloned, expressed in COS-7 cells, and characterized pharmacologically. Competition binding studies of several Adrenergic ligands with the three human receptor subtypes reveals a distinct pharmacological profile for each receptor subtype. RNase protection analysis demonstrates that the three receptor subtypes have different patterns of distribution in human tissue. The availability of the three human Alpha 1 receptor subtypes will facilitate the development of subtype-selective Alpha 1 antagonists for a variety of therapeutic indications.
D C Haggerty - One of the best experts on this subject based on the ideXlab platform.
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bidirectional modulation of hippocampal gamma 20 80 hz frequency activity in vitro via Alpha α and beta β Adrenergic Receptors ar
Neuroscience, 2013Co-Authors: D C Haggerty, V Glykos, Natalie E Adams, Fiona E N LebeauAbstract:Abstract Noradrenaline (NA) in the hippocampus plays an important role in memory function and has been shown to modulate different forms of synaptic plasticity. Oscillations in the gamma frequency (20–80 Hz) band in the hippocampus have also been proposed to play an important role in memory functions and, evidence from both in vitro and in vivo studies, has suggested this activity can be modulated by NA. However, the role of different NA receptor subtypes in the modulation of gamma frequency activity has not been fully elucidated. We have found that NA (30 μM) exerts a bidirectional control on the magnitude of kainate-evoked (50–200 nM) gamma frequency oscillations in the cornu Ammonis (CA3) region of the rat hippocampus in vitro via activation of different receptor subtypes. Activation of Alpha-Adrenergic Receptors (α-AR) reduced the power of the gamma frequency oscillation. In contrast, activation of beta-Adrenergic Receptors (β-AR) caused an increase in the power of the gamma frequency oscillations. Using specific agonists and antagonists of AR receptor subtypes we demonstrated that these effects are mediated specifically via α1A-AR and β1-AR subtypes. NA activated both receptor subtypes, but the α1A-AR-mediated effect predominated, resulting in a reversible suppression of gamma frequency activity. These results suggest that NA is able to differentially modulate on-going gamma frequency oscillatory activity that could result in either increased or decreased information flow through the hippocampus.
J S Landzberg - One of the best experts on this subject based on the ideXlab platform.
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effects of myocardial Alpha 1 Adrenergic receptor stimulation and blockade on contractility in humans
Circulation, 1991Co-Authors: J S Landzberg, J D Parker, D F Gauthier, Wilson S ColucciAbstract:BACKGROUNDAlthough Alpha-Adrenergic Receptors are present in both normal and failing human left ventricular myocardium and mediate a positive inotropic effect in several other species, it is not known whether stimulation of myocardial Alpha-Adrenergic Receptors exerts a positive inotropic effect or contributes to basal contractile state in vivo in humans.METHODS AND RESULTSWe studied 15 patients with angiographically normal coronary arteries (seven with normal left ventricular function and eight with left ventricular failure). To avoid the confounding effects of changes in ventricular loading conditions and systemic reflex mechanisms, the Alpha-Adrenergic receptor-selective antagonist phentolamine and agonist phenylephrine were infused directly into the left main coronary artery, and the change in contractile state was assessed by measuring left ventricular peak (+)dP/dt. Phentolamine alone had no effect on left ventricular contractility. Phenylephrine exerted a concentration-related positive inotropic ef...