Jan-Bjørn Osnes

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Activation of 5-HT(4) receptors in failing ventricles elicits a cAMP-dependent positive inotropic response which is mainly limited by the cGMP-inhibitable phosphodiesterase (PDE) 3. However, PDE4 plays an additional role which is demasked by PDE3 inhibition. The objective of this study was to evaluate the effect of cGMP generated by particulate and soluble(More)
A positive inotropic responsiveness to serotonin, mediated by 5-HT(4) and 5-HT(2A) receptors, appears in the ventricle of rats with post-infarction congestive heart failure (HF) and pressure overload-induced hypertrophy. A hallmark of HF is a transition towards a foetal genotype which correlates with loss of cardiac functions. Thus, we wanted to investigate(More)
Previously, cardioexcitation by serotonin (5-hydroxytryptamine, 5-HT) was believed to be confined to atria in mammals including man, and mediated through 5-HT(4) receptors in pig and man, but 5-HT(2A) receptors in rat. Recent studies, reviewed here, demonstrate that functional 5-HT(4) receptors can be revealed in porcine and human ventricular myocardium(More)
Studies suggest that increased activity of Gi contributes to the reduced β-adrenoceptor-mediated inotropic response (βAR-IR) in failing cardiomyocytes and that β2AR-IR but not β1AR-IR is blunted by dual coupling to Gs and Gi. We aimed to clarify the role of Gi upon the β1AR-IR and β2AR-IR in Sham and failing myocardium by directly measuring contractile(More)
Background: A recent meta-analysis of drug effects in patients with hypertension claims that all β-adrenergic blockers are equally effective but less so than other antihypertensive drugs. Published comparisons of the β-adrenergic blocker atenolol and non-atenolol β-adrenergic blockers indicate different effects on death rates, arrhythmias, peripheral(More)
We found previously that stimulation of natriuretic peptide receptor (NPR)-B by C-type natriuretic peptide (CNP) in failing rat ventricle potentiates β1-adrenoceptor (β1-AR)-mediated inotropic response to noradrenaline through cGMP-mediated inhibition of phosphodiesterase (PDE) 3, thereby enhancing cAMP-mediated signalling. Increased cAMP-mediated(More)
AIMS We recently published that the positive inotropic response (PIR) to levosimendan can be fully accounted for by phosphodiesterase (PDE) inhibition in both failing human heart and normal rat heart. To determine if the PIR of the active metabolite OR-1896, an important mediator of the long-term clinical effects of levosimendan, also results from PDE3(More)
BACKGROUND AND PURPOSE Despite the view that only β2- as opposed to β1-adrenoceptors (βARs) couple to G(i), some data indicate that the β1AR-evoked inotropic response is also influenced by the inhibition of Gi. Therefore, we wanted to determine if Gi exerts tonic receptor-independent inhibition upon basal adenylyl cyclase (AC) activity in cardiomyocytes. (More)