Meeting Abstract
Dipterans, like vertebrates, are subject to circadian rhythms. Circadian rhythms can cause physiological changes that lead to differences in behavioral responses throughout the day. These physiological changes include fluctuations in monoamine levels, such as dopamine. Invertebrates, like stalk-eyed flies (Teleopsis dalmanni), are a useful model for studying the function of conserved mechanisms, like monoamines, that are also seen in vertebrates. We designed a circadian rhythm study in which flies were sacrificed every four hours and used HPLC with electrochemical detection (ED) to detect changes in whole-brain levels of dopamine, serotonin, and octopamine throughout the day. Octopamine and serotonin stayed relatively level throughout the day in both males and females. Female stalk-eyed flies were found to have a spike in dopamine levels from 6 to 10 pm, which is when they tend to roost, while male levels stayed stable. This spike was not seen at other times throughout the day. We hypothesized that this spike in dopamine would lead to increased mating receptivity in females. To test this, we administered 3-Iodo-L-tyrosine 97%, which inhibits the enzyme Tyrosine Hydroxylase and decreases the synthesis of L-Dopa, to knock down dopamine globally in female flies. Both control and treated females were isolated from males, who were also isolated from other females, for three days while the drug was being administered. Then mating receptivity was assessed, recorded, and scored. HPLC with ED and Immunohistochemistry were used as validation methods to ensure that dopamine was knocked down. The results supported the hypothesis that a circadian increase in dopamine plays a significant role in mating receptivity in female stalk-eyed flies.
