Influence of long-term treatment with ketanserin on blood pressure, pulmonary artery pressure, and cardiac output in patients with heart failure

Contribution of gene-modified mice and rats to our understanding of the cardiovascular pharmacology of serotonin

This review focuses on new insights provided by gene-modified animals into the cardiovascular pharmacology of serotonin. During their development, mice mutant for tryptophan hydroxylase 1 and lacking peripheral serotonin, or mutant for 5-HT(2B) receptors, display cardiac defects and dilated cardiomyopathy. The 5-HT(4) receptor is important for the maturation of cardiac conduction. In fact, transgenic approaches have revealed that adult cardiac status is strongly influenced by maternal serotonin. Serotonin has long been known to be a vasoconstrictor in adult physiology. Analysis of animals knocked-out for the serotonin transporter suggested a role in blood pressure control and revealed an effect of 5-HT(2B) receptor antagonists in hypertension. In the lung vasculature, mice lacking the 5-HT(2B) receptor gene that are exposed to chronic hypoxia are resistant to pulmonary hypertension, while 5-HT(1B) receptor and serotonin transporter mutant animals show partial resistance. In platelets, mutant mice revealed that serotonin transporter regulates not only the mechanisms by which serotonin is packaged and secreted but also platelet aggregation. Studies looking at adult cardiac remodeling showed that mice lacking the 5-HT(2B) receptor gene were protected from cardiac hypertrophy. Their fibroblasts were unable to secrete cytokines. Crossing these animals with mice overexpressing the receptor in cardiomyocytes revealed the contribution of cardiac fibroblasts and 5-HT(2B) receptors to cardiac hypertrophy. In mice lacking the monoamine oxidase-A gene, the role of serotonin degradation in cardiac hypertrophy was confirmed. Works with gene-modified animals has contributed strongly to the re-evaluation of the influence of serotonin on cardiovascular regulation, though several unknowns remain to be investigated.

Antiplatelet therapy mitigates cardiac remodeling and dysfunction in congestive heart failure due to myocardial infarctionThis article is one of a selection of papers published in the special issue Bridging the Gap: Where Progress in Cardiovascular and Neurophysiologic Research Meet

Antiplatelet agents such as sarpogrelate (SAR), a 5-hydroxytryptamine antagonist, and cilostazol (CIL), a phosphodiesterase-III inhibitor, are used in the management of peripheral vascular disease. In this study, we tested the hypothesis that both SAR and CIL prevent cardiac remodeling and improve cardiac function in congestive heart failure (CHF) due to myocardial infarction (MI). Post-MI rats (3 weeks after the occlusion of coronary artery) received either vehicle (MI+V, n = 36), SAR (MI+SAR; 5 mg·kg–1·day–1, n = 35) or CIL (MI+CIL; 5 mg·kg–1·day–1, n = 34) from day 21 to day 56. Sham-operated rats (n = 29) served as controls. Electrocardiographic, echocardiographic, and hemodynamic parameters were measured on day 56. Treatment of infarcted animals with SAR or CIL significantly improved the left ventricular (LV) dimensions, LV fractional shortening, cardiac output, stroke volume, mean arterial pressure, LV diastolic function, and LV systolic pressure, as well as rates of LV pressure development and pressure decay. Although cardiac hypertrophy was reduced, both SAR and CIL had no effect on infarct size or MI-associated QTc prolongation. However, SAR decreased whereas CIL increased the incidence of ventricular arrhythmias and the mean number of episodes in infarcted animals. Mortality during the treatment period was decreased by 17% with SAR and increased by 10% with CIL, but these changes were not significant statistically. The data in this study suggest that both SAR and CIL prevent cardiac remodeling and improve cardiac function in MI-induced CHF; however, CIL unlike SAR increased the incidence of arrhythmias and adversely affected patient mortality.

Serotonin and serotonin antagonism in cardiovascular and non-cardiovascular disease

Serotonin, or 5-hydroxytryptamine, is a naturally-occurring vasoactive substance found primarily in the brain, enterochromaffin tissue, and blood platelets. It has diffuse cardiophysiologic effects. The multiple effects of serotonin on blood vessels can be explained by the existence of 2 serotonergic receptor subtypes (the S1 receptor mediates vasodilation, and the S2 receptor vasoconstriction). Serotonin via the S2 receptor also augments the actions of several other vasoconstricting substances. Serotonin may be responsible for causing, or at least perpetuating, some forms of systemic hypertension through peripheral and central nervous system (CNS) actions. Ketanserin is a highly selective S2-serotonergic antagonist with additional alpha-adrenergic blocking activity, which has been proposed as a therapy for various cardiovascular diseases including hypertension. It has been shown to be more effective than placebo in treating hypertension and comparable in effectiveness to other antihypertensive drugs. Its major side effects relate to the CNS, and prolongation of the electrocardiogram QT interval has been described. Caution must be used when using ketanserin in patients receiving potassium- and magnesium-losing agents, because of the risk of torsades de pointes. Ketanserin has potential utility in the treatment of eclampsia, peripheral vascular disease, carcinoid syndrome, and "shock lung." The drug is not yet approved for clinical use in the United States.