Punishing Effect of Rhodiola rosea in larval Drosophila melanogaster

Abstract

The aim of this thesis is to investigate the reinforcing effects that R. rosea has in larval D. melanogaster, an established study case for associative learning. R. rosea root material was previously known to have a rewarding effect in a one-odor learning paradigm in D. melanogaster larvae. Here it is shown that, in addition, this plant material has as punishing effect. Given that a compound that can mediate the rewarding effects of R. rosea has recently been identified, it was the aim of this thesis to identify the chemical compound(s) responsible for the punishing effect. Towards this end a bio-assay guided fractionation with activity-correlation analysis was performed. Each fractionation step was tested in the one-odor learning paradigm for effectiveness. In the end a single compound could not be identified. The results suggest, however, that the punishing and the rewarding effects of R. rosea are not mediated by the very same compound. The second part of this thesis focuses on the neuronal circuitry underlying the punishing effect of R. rosea in D. melanogaster larvae. Transgenic manipulation of the larval mushroom body, a brain area known for memory formation, was performed using the UAS/ Gal4 system. UAS-KirGFP/ OK107-Gal4 animals showed impairments in R. rosea extract punishment memory. However, experiments for innate responses towards odor and R. rosea extract showed differences to genetic control animals, such that these differences might partially account for the observed punishment memory defects.