Mosapride produces its gastrokinetic effects by acting as an agonist at which of the following receptor?

Ans. is 'd' i.e., 5HT4 Mosapride* It is a congener of cisapride with similar gastrokinetic and LES tonic action due to 5-HT4 agonistic (major) and 5-HT3 antagonistic (minor) action in the myenteric plexus.* Like cisapride, it has no clinically useful antiemetic action and does not produce extrapyramidal or hyperprolactinaemic side effects because of absence of D2 blocking property.* Side effects are diarrhoea, abdominal pain, headache, dizziness and insomnia.* Preclinical studies showed that it may not have the potential to prolong Q-T interval and carry risk of arrhythmias. Therefore, it was introduced as a safe prokinetic. However, after general use some reports of Q-T prolongation and arrhythmias, including torsades de pointes , among recipients have appeared.* Like cisapride, its plasma concentration is elevated by erythromycin and other CYP3A4 inhibitors increasing the risk of Q-T prolongation.* Though, it has not been banned, it may not be as safe as considered earlier.* Indications of mosapride are--nonulcer dyspepsia, diabetic gastroparesis, GERD (as adjuvant to H2 blockers/ PPIs), and some cases of chronic constipation. However, efficacy is not impressive.