Serotonin modulates the heart rate through 5‐HT2 receptor activation in Drosophila larvae (1100.7)

Abstract

Serotonin, 5‐HT, plays various roles in the fruit fly, Drosophila melanogaster. Previous studies have shown that 5‐HT modulates the heart rate in third instar larvae. However, 5‐HT receptor subtypes that mediate 5‐HT action in larval cardiac tissue has not yet been determined. In this study, various 5‐HT agonists and antagonists were employed to determine which 5‐HT receptor subtypes are responsible for the positive chronotropic effect by 5‐HT. The pharmacological results demonstrate that a 5‐HT2B agonist significantly increases the heart rate; however, 5‐HT1A, 5‐HT1B, and 5‐HT7 agonists do not have a significant effect on the heart rate. Furthermore, 5‐HT2 antagonist, ketanserin, markedly reduces the positive chronotropic effect of 5‐HT in a dose‐response manner. Furthermore, we employed genetic approaches to confirm the pharmacological results. For this propose, we used RNA interference (RNAi) line to knock down 5‐HT2ADro and also used 5‐HT2ADro and 5‐HT2BDro insertional mutation lines. The results show that 5‐HT2ADro or 5‐HT2BDro receptors mutation reduces the response of heart to 5‐HT. Given these results, we conclude that 5‐HT2 receptors activation are involved in the action of 5‐HT on the heart rate in the larval stage.