Nagoya University discovers female auditory sensory cell sensitivity flexibly regulated by dopamine

A research group led by Professor Azusa Kamikouchi of the Institute of Transformative Bio-Molecules and Graduate Student Haruna Yamakoshi of the Graduate School of Science at Nagoya University announced that they have discovered that dopaminergic signals can flexibly regulate the sensitivity of auditory sensory cells in female Drosophila. This flexible sound processing capability achieved through dopamine is common across many animals, and it is expected to lead to an understanding of this neural processing mechanism in the brain. The results were published in the July 29 issue of iScience.

Sound is one of the means by which organisms obtain information, and responsiveness to sound is flexibly regulated according to circumstances. This mechanism exists to effectively allocate limited brain resources to important information, and research using model animals has shown that the brain's responsiveness to sound changes with dopamine, a neurotransmitter. However, the neural mechanisms that enable this were unknown.

Male Drosophila melanogaster produce wing sounds with unique rhythms (courtship songs) to court females, and females listen to these sounds to decide whether to accept courtship. These flies perceive sound through vibrations of their antennae, and within the antennae are auditory sensory cells (neurons in Johnston's organs (JO)) that transmit sound information to the brain through their extending axons.

Previously, the research group discovered in 2020 that the neurons of JO in Drosophila have many postsynaptic sites that receive input from other neurons. This suggested the possibility that the responsiveness of JO neurons is regulated by other neurons in the brain. As a result, in this study, the research group first comprehensively examined genes expressed in JO neurons using single-nucleus RNA-seq to investigate which neurotransmitters regulate them.

They found that dopamine receptors are expressed in JO neurons. Since brain dopamine levels fluctuate according to mating drive in mice and flies, they were thought to receive dopamine at certain times.

To examine involvement in mating drive, the group measured neural responses of JO neurons to sound using unmated females (high mating drive) and mated females (low mating drive). They expressed a protein that increases fluorescence intensity according to calcium concentration within JO neurons and detected their sound responses as fluorescence changes.

The results showed that dopamine signals enhanced the response of JO neurons only in unmated females, while there was no change in mated females even when dopamine signals were present.

Next, they verified whether the enhanced responsiveness in unmated females increased responsiveness to actual courtship songs. Using the time until mating acceptance after hearing courtship songs as an indicator, they investigated whether responses changed with suppression of dopamine receptor expression.

The results showed that expression suppression reduced mating acceptance behavior in unmated females.

Dopamine signals increased auditory responsiveness, which enhanced mating responsiveness in unmated females with high mating drive. On the other hand, it was revealed that while auditory responsiveness increased in mated females with low mating drive, mating responsiveness did not increase.

Kamikouchi commented: "In the future, we would like to clarify where dopamine comes from and how mating drive is perceived. We hope to connect this to elucidating the mechanisms of how flexible brain function control actually operates in various neural cells in response to various sensory stimuli."

Yamakoshi commented: "In this research we investigated the auditory sensory neurons that first receive sound, but in the future, we would like to investigate higher-order neurons in the brain as well."

Journal Information
Publication: iScience
Title: Mating status-dependent dopaminergic modulation of auditory sensory neurons in Drosophila
DOI: 10.1016/j.isci.2025.113232