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

IntroductionThe purpose of these studies was to describe a novel application of an automated data acquisition/data reduction system, DanioVision™ by Noldus. DanioVision™ has the ability to detect changes in locomotor activity in third instar Drosophila melanogaster larvae. The noncompetitive GABAA receptor antagonist picrotoxin (PTX), was used as a pharmacologic agent to decrease locomotor activity.MethodsTwo strains of Drosophila were used in these studies; wild-type flies and flies with a mutation in the Rdl gene (RdlMD-RR). RdlMD-RRDrosophila are naturally occurring mutants that express an aberrant form of the GABAA 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™ apparatus. The activity of individual larva was recorded for 5 min, digitized and analyzed using Ethovision® XT software.ResultsIncubation 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 mM resulted in variable decreases in locomotor activity and 0.03 mM yielded no effect. By contrast, PTX did not affect activity in RdlMD-RR larvae even at the highest concentration, 3.0 mM.DiscussionUsing an automated data acquisition system, it was found that PTX decreases activity in third instar Drosophila larvae due to a selective blockade of the GABAA 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.