HTR2B and heart valve disorder: For instance, the use of pergolide, a dopamine D2 receptor agonist that is approved for the treatment of PD, has been limited due to the increased risk of fibrotic valvular heart disease [42] related to the ability of this drug to activate the 5-hydroxytryptamine receptor 2B (HTR2B) serotonin receptors and the transforming growth factor beta (TGF-β) pathway [43,44].