An automated method to assay locomotor activity in third instar Drosophila melanogaster larvae

Introduction: The purpose of these studies was to describe a novel application of an automated data acquisition/data reduction system, DanioVision (TM) by Noldus. DanioVision (TM) has the ability to detect changes in locomotor activity in third instar Drosophila melanogaster larvae. The noncompetitive GABA(A) receptor antagonist picrotoxin (PTX), was used as a pharmacologic agent to decrease locomotor activity. Methods: Two strains of Drosophila were used in these studies; wild-type flies and flies with a mutation in the Rdl gene (Rdl(MD) (RR)). Rdl(MD) (RR) Drosophila are naturally occurringmutants that express an aberrant form of the GAB(AA) receptor, which has a lower affinity for PTX, but not GABA itself. Larvae, extracted from food in 20% sucrose, were randomly placed into vials containing vehicle or PTX (0.03-3 mM). After incubation of 2-24 h, individual larvae were put in each well of a 6-well culture plate previously coated with 2% agar, the plate was then placed in the DanioVision (TM) apparatus. The activity of individual larva was recorded for 5 min, digitized and analyzed using Ethovision (R) XT software. Results: Incubation of third instar wild-type larvae in 1 mM PTX for 4 or 24 h decreased activity; whereas, a 2 h incubation in PTX was without effect. PTX caused a concentration-dependent decrease in activity as demonstrated by consistently reduced locomotor activity with 1.0 and 3.0 mM: 0.3 mMresulted in variable decreases in locomotor activity and 0.03 mM yielded no effect. By contrast, PTX did not affect activity in Rdl(MD-RR) larvae even at the highest concentration, 3.0 mM. Discussion: Using an automated data acquisition system, it was found that PTX decreases activity in third instar Drosophila larvae due to a selective blockade of the GABA(A) receptor. The method will reduce the likelihood of human error and bias, as well as increase the speed and ease of data collection and analysis. (C) 2015 Elsevier Inc. All rights reserved.