Neuronal underpinning of reproductive state dependent olfactory behavior in Drosophila

Böhm, Ariane (2019): Neuronal underpinning of reproductive state dependent olfactory behavior in Drosophila. Dissertation, LMU München: Graduate School of Systemic Neurosciences (GSN)

Abstract

A general question in neuroscience is how the flow of sensory information is encoded towards a behavioral response. These behavioral responses can be interpreted as decisions the organism needs to make to get a most beneficial outcome. Factors which can influence these decisions can be external or internal. Considering sensory information, external stimuli can elicit "innate" responses to a sensory input, which lead to a certain behavior. Interestingly, these responses can be overwritten given a certain experience or context. The internal state of an organism can be such a context. Internal states, such as age, stress, hunger, or reproductive state can have effects on chemosensory decision making behavior. Such behavior usually manifests itself by attraction or aversion towards a certain odor or taste. Occasionally, transient neuromodulation can affect these behaviors, by focusing an animal's attention to relevant sensory stimuli in its environment. This might facilitate remembering relevant vs. irrelevant stimuli. Here, we are investigating the role of such a sensory neuromodulation and the formation of memory in the female fruit fly, Drosophila melanogaster. Previous work from our lab has shown that mating changes the sensitivity of olfactory and gustatory neurons with the help of specific neuromodulators that act directly on these chemosensory neurons. However, this very transient neuromodulation leads to a long-term behavioral change in females: for instance, while virgin flies usually prefer low concentrations of polyamines, mated flies will prefer higher concentrations after the mating experience and will continue this behavior for up to two weeks until falling back to a virgin-like state. Drosophila's genetic toolset allows us to test the hypothesis that this transient sensory enhancement facilitates the formation of a long-lasting memory. Using a quantitative olfactory choice assay, my collaborators and I silenced and activated neuronal activity in different parts of the fly's associative memory center (i.e. the mushroom body). We revealed a possible neuronal pathway and its modulatory switch between virgin and mated state. These findings suggest that dopaminergic neurons, which are innervating the mushroom body, control virgin vs. mated female behavior by processing sensory input differentially before and after mating, respectively. Furthermore, our data suggests that courtship and pheromones are highly important signals to trigger the reproductive state dependent change in olfactory preference behavior. In addition, my collaborators and I wanted to use state-of-the-art techniques to shed light on the detection of nutrients valuable for the gravid fly by using bioinformatic tools and to promote these methods to the biological fields. As two-photon laser scanning microscopy is an important tool for neuroscientific research in the fly and beyond, I built such a microscope. Harnessing this experience, I have, in collaboration, written a guide for life scientists wishing to build or purchase such a microscope. A joint effort between established behavioral assays and technological advances, such as bioinformatic tools, can support and extend our understanding of neuronal circuits underlying reproductive state dependent behaviors.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie
• Fakultäten: Graduate School of Systemic Neurosciences (GSN)
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 22. Juli 2019
• 1. Bericht­erstatter:in: Grunwald Kadow, Ilona