Quantitative trait loci for the monoamine-related traits heart rate and headless behavior in Drosophila melanogaster

Drosophila melanogaster appears to be well suited as a model organism for q uantitative pharmacogenetic analysis. A genome-wide deficiency screen for h aploinsufficient effects on prepupal heart tate identified nine regions of the genome that significantly reduce (five deficiencies) or increase (four deficiencies) heart rate across a. range of genetic backgrounds. Candidate genes include several neurotransmitter receptor loci, particularly monoamin e receptors, consistent with results of prior pharmacological manipulations of heart rate, as well as genes associated with paralytic phenotypes. Sign ificant genetic variation is also shown to exist for a suite of four autono mic behaviors that are exhibited spontaneously upon decapitation, namely, g rooming, grasping, righting, and quivering. Overall activity levels are inc reased by application of particular concentrations of the drugs octopamine and nicotine, but due to high environmental variance both within and among replicate vials, the significance of genetic variation among wild-type line s for-response to the drugs is difficult to establish. An interval mapping design was also used to map two or three QTL for each behavioral trait in a set of recombinant inbred lines derived from the laboratory stocks Oregon- R and 2b.