Slow presynaptic mechanisms that mediate adaptation in the olfactory pathway of Drosophila

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Abstract

The olfactory system encodes odor stimuli as combinatorial activity of populations of neurons whose response depends on stimulus history. How and on which timescales previous stimuli affect these combinatorial representations remains unclear. We use in vivo optical imaging in Drosophila to analyze sensory adaptation at the first synaptic step along the olfactory pathway. We show that calcium signals in the axon terminals of olfactory receptor neurons (ORNs) do not follow the same adaptive properties as the firing activity measured at the antenna. While ORNs calcium responses are sustained on long timescales, calcium signals in the postsynaptic projection neurons (PNs) adapt within tens of seconds. We propose that this slow component of the postsynaptic response is mediated by a slow presynaptic depression of vesicle release and enables the combinatorial population activity of PNs to adjust to the mean and variance of fluctuating odor stimuli.

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All data generated or analyzed during this study are included in the manuscript and supporting files.

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Carlotta Martelli

Department of Molecular Neurobiology of Behavior, Georg-August-Universität Göttingen, Göttingen, Germany

For correspondence
carlotta.martelli@uni-konstanz.de

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-5663-6580
André Fiala

Department of Molecular Neurobiology of Behavior, Georg-August-Universität Göttingen, Göttingen, Germany

Competing interests
The authors declare that no competing interests exist.

Funding

Alexander von Humboldt-Stiftung (Postdoctoral Fellowship)

Carlotta Martelli

Deutsche Forschungsgemeinschaft (SFB 889/B4)

André Fiala

University of Konstanz

Carlotta Martelli

Zukunftskolleg of the University of Konstanz

Carlotta Martelli

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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