title: Octopamine indirectly affects proboscis extension response habituation in Drosophila melanogaster by controlling sucrose responsiveness.
abstract: Octopamine is an important neurotransmitter in insects with multiple functions. Here, we investigated the role of this amine in a simple form of learning (habituation) in the fruit fly Drosophila melanogaster. Specifically, we asked if octopamine is necessary for normal habituation of a proboscis extension response (PER) to different sucrose concentrations. In addition, we analyzed the relationship between responsiveness to sucrose solutions applied to the tarsus and habituation of the proboscis extension response in the same individual. The Tyramine-β-hydroxylase (Tβh) mutant lacks the enzyme catalyzing the final step of octopamine synthesis. This mutant was significantly less responsive to sucrose than controls. The reduced responsiveness directly led to faster habituation. Systemic application of octopamine or induction of octopamine synthesis by Tβh expression in a cluster of octopaminergic neurons within the suboesophageal ganglion restored sucrose responsiveness and habituation of octopamine mutants to control level. Further analyses imply that the reduced sucrose responsiveness of Tβh mutants is related to a lower sucrose preference, probably due to a changed carbohydrate metabolism, since Tβh mutants survived significantly longer under starved conditions. These findings suggest a pivotal role for octopamine in regulating sucrose responsiveness in fruit flies. Further, octopamine indirectly influences non-associative learning and possibly associative appetitive learning by regulating the evaluation of the sweet component of a sucrose reward.
authors.affiliation: Universität Potsdam, Institut für Biochemie und Biologie, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany. Electronic address: rscheine@uni-potsdam.de.
authors.forename: Ricarda
authors.initials: R
authors.lastname: Scheiner
authors.affiliation: Universität Potsdam, Institut für Biochemie und Biologie, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Steinbach
authors.affiliation: Universität zu Köln, Institut für Zoologie, Zülpicher Strasse 47b, Biozentrum, 50674 Köln, Germany.
authors.forename: Gerbera
authors.initials: G
authors.lastname: Claßen
authors.affiliation: Universität zu Köln, Institut für Zoologie, Zülpicher Strasse 47b, Biozentrum, 50674 Köln, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Strudthoff
authors.affiliation: Universität zu Köln, Institut für Zoologie, Zülpicher Strasse 47b, Biozentrum, 50674 Köln, Germany. Electronic address: henrike.scholz@uni-koeln.de.
authors.forename: Henrike
authors.initials: H
authors.lastname: Scholz
mesh_terms: D000818:Animals; D001835:Body Weight; D004331:Drosophila melanogaster / Q000502:physiology*; D004435:Eating / Q000502:physiology*; D005518:Food Preferences / Q000502:physiology; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D009154:Mutation; D009655:Octopamine / Q000502:physiology*; D011897:Random Allocation; D011984:Sensory Receptor Cells / Q000502:physiology; D013395:Sucrose; D013649:Taste / Q000502:physiology
chemical_list: D009655:Octopamine; D013395:Sucrose
keywords: Biogenic amine; Learning; Life span; Nutrition; Sucrose responsiveness; Tβh