Influence of 5-HT Receptors on Behavior and Heart Rate in Drosophila Melanogaster Larvae

The serotonin-ergic systems in nervous tissue is known to play a vital role in development and behavior in simple to complex animal models. To have effective and differential responses to serotonin (5-HT) in various tissues there are multiple types of 5- HT receptors. In the Drosophila genome there are only four 5-HT receptors, thus to understand the role in development and importance of the 5-HT circuitry and actions on target tissue we use the genetically manipulatable fly model. Among the 4 receptors in fly, the 5-HT2dro is known to be essential in the embryonic stages of development. Also the expression profile of 5-HT2dro has been shown to be a major receptor in the 3rd instar larvae. We are assessing the role of 5-HT2dro receptor in 3rd instar larva using two different temperature sensitive mutant lines, HsZ2 and Y32 for the dysfunction of the receptor. Our preliminary studies with these mutants have shown that mouth-hook movements and body wall movements are decreased compared to Canton S (wild type). The heart rate of wild type larval Drosophila is enhanced by serotonin (5-HT). 5HT (1uM/l) injected into 3rd instars increases HR by 46%. Our studies have shown that an exogenous application of 5-HT on the heart in a semi-intact preparation increases the heart rate in dose response fashion. The heart rate in the HsZ2 and Y32 mutant lines is currently being investigated along with the sensitivity of the larvae CNS to exogenously applied 5-HT in controls and mutant 5-HT receptor lines