HTR4 and gastroparesis: Several new pharmacological agents targeting specific receptors are currently being developed for gastroparesis, such as neurokinin 1 antagonist (tradipitant), synthetic ghrelin agonist (relamorelin), and highly selective 5-Hydroxytryptamine receptor 4 (5-HT4) agonists (velusetrag, prucalopride, felcisetrag) [5-12].