Circadian modulation of dopamine receptor responsiveness in Drosophila melanogaster

We investigated the circadian function of Drosophila dopamine receptors by using a behaviorally active decapitated preparation that allows for direct application of drugs to the nerve cord. Quinpirole, a D2-like dopamine rece ptor agonist, induces reflexive locomotion in decapitated flies. We show th at the amount of locomotion induced changes as a function of the time of da y, with the highest responsiveness to quinpirole during the subjective nigh t. Furthermore, dopamine receptor responsiveness is under circadian control and depends on the normal function of the period gene. The head pacemaker is at least partly dispensable for the circadian modulation of quinpirole-i nduced locomotion, because changes in agonist responsiveness persist in dec apitated flies that are aged for 12 h, This finding suggests a role for the period-dependent molecular oscillators in the body in the modulation of am ine receptor responsiveness.