Uniform pattern of immunohistochemical localization of serotonin 5-HT2 receptors in human aortic, mitral, pulmonary and tricuspid heart valves: Implication for the pathomechanism of valvular heart disease following treatment with dopamine agonists

It has been suggested that the activation of the serotonin (5-hydroxytryptamine, 5-HT) receptor family 5-HT2, in particular the subtype 5-HT2B, is a key step in the progression of drug-induced valvular heart disease (VHD). However, the localisation of 5-HT2 receptors in human valves have not been reported. Thus, the current study investigated the regional and cellular localization of 5-HT2 receptors in the tricuspid, mitral, aortic and pulmonary heart valves of six humans (n = 24 samples) by immunohistochemistry post-mortem. We found that 5-HT2A and 5-HT2B receptors are present in all examined heart valves, whereas 5-HT2C receptors were either not present or scarcely found. Interestingly, we found a uniform pattern of 5-HT2B receptor numbers in all heart valves examined. Our results confirm patterns reported in echocardiographic investigations in patients with Parkinson's disease treated with cabergoline and pergolide and suggest that the 5-HT2 receptor located in heart valves may play a role in the drug-induced VHD.