A novel injection technique for the measurement of drug-related behaviors in unanesthetized fruit flies.

BACKGROUND

Behavioral pharmacological studies in rats and mice often measure behavioral responses to ethanol or other drugs administered by injection, such that the timing of the injection provides a convenient point of reference to index the effects of the drug. Although a variety of drug administration protocols have been developed for use with the fruit fly Drosophila melanogaster, currently available techniques do not allow for a comparable bolus administration of drugs to awake, behaving flies.

NEW METHOD: We developed a novel apparatus that temporarily restrains and orients unanesthetized fruit flies for an intra abdominal injection. Using this apparatus, we injected male and female flies with a constant 200 nL volume of ethanol at varying concentrations (0-50% v/v), then measured acute and protracted behavioral changes as well as survivability following the injections.

RESULTS

Ethanol produced an acute biphasic effect on locomotor activity and dose-dependent increase in immobility as measured by a loss-of-righting response assay, with no significant differences by sex. A protracted, sex-dependent effect of ethanol injection was also found on the rate of locomotion measured before exposure to ethanol vapor, with male flies showing increased locomotion when measured 28 h after injection.

COMPARISON WITH EXISTING

METHODS

Ethanol-related behaviors following injections resemble those produced by vapor exposure. However, poor survivability after the injection will likely limit the procedure to studies of acute drug responses.

CONCLUSION

Our results suggest that this injection procedure might prove useful for characterizing ethanol and drug responses in fruit flies.