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Discovery of key neural mechanisms in fruit fly mating behavior

Researchers have illuminated the role of inhibitory functions in the brain and their influence on behavior by studying the intrinsic courtship ritual of Drosophila, commonly known as fruitflies.

Graphic of the GABAergic inhibition in Drosophila male courtship
Anne von philipsborn
Stella Solveig Nolte

In many species, courtship behaviour is characterized by a set of relatively fixed and stereotypical actions or rituals that individuals of the species perform during the process of attracting and engaging potential mates.

Studying these fixed behaviours offers valuable insights into the brain’s neural mechanisms, including neural plasticity, evolutionary adaptations etc.

For former DANDRITE Group Leader Anne von Philipsborn this has been the centre of her research for many years, and she just recently published a new article based on the work from her time at DANDRITE.

Male-fly courtship serves as a model for circuit behavior
In the article, Anne and her former group reveal new insights into the intrinsic role of inhibitory GABAergic neurons in the male courtship of fruit flies (Drosophila). 

For Drosophila, courtship consists of multiple coordinated and ordered steps relying on multimodal sensory integration and the generation of specific, precisely timed motor patterns.

Characteristic courtship displays are the male tracking and following the female, tapping her abdomen with the foreleg to sample pheromones and vibrating one extended wing. The wing vibrations produce a highly structured acoustic signal, the courtship song that stimulates the female’s receptivity and promotes her acceptance of copulation.

According to several studies, the neuronal circuits underlying male fly courtship are among the best-studied model circuits for behaviour in the Drosophila nervous system, and thus a unique model for addressing the question of how neuronal inhibition shapes a complex behavioural sequence.

Reducing GABA disturbs  behavior
By studying a sex-specific type of inhibitory nerve cells in male fruit flies that use the neurotransmitter GABA, they are able to conclude, that these nerve cells play a crucial role in organizing and shaping the different actions involved in male courtship.

When they reduced GABA in these nerve cells, the male flies had trouble with their mating attempts. They couldn't coordinate their movements properly, had problems choosing the right time to extend their wings, and their courtship songs lost structure and rhythm.

Interestingly, the changed courtship songs were not effective in getting female flies in the mood for mating. Fixing just the song didn't help the males succeed in mating, indicating that many other aspects of fine motor control were affected.

The scientists identified about 220 of these nerve cells in male fruit flies, and they suggest that these cells work together in networks to control various aspects of the mating process. In other words, neuronal inhibiton play a key role in how male fruit flies behave when trying to court and mate with female fruit flies.

The article is published in iScience in November 2023.