Botulinum neurotoxin accurately separates tonic vs phasic transmission and reveals heterosynaptic plasticity rules in Drosophila
In developing and mature nervous systems, diverse neuronal subtypes innervate common targets to establish, maintain, and modify neural circuit function. A major challenge towards understanding the structural and functional architecture of neural circuits is to separate these inputs and determine their intrinsic and heterosynaptic relationships. The Drosophila larval neuromuscular junction is a powerful model system to study these questions, where two glutamatergic motor neurons, the strong phasic-like <strong>Is</strong> and weak tonic-like <strong>Ib</strong>, co-innervate individual muscle targets to coordinate locomotor behavior. However, complete neurotransmission from each input has never been electrophysiologically separated. We have employed a botulinum neurotoxin, BoNT-C, that eliminates both spontaneous and evoked neurotransmission without perturbing synaptic growth or structure, enabling the first approach that accurately isolates input-specific neurotransmission. Selective expression of BoNT-C in Is or Ib motor neurons disambiguates the functional properties of each input. Importantly, the blended values of Is+Ib neurotransmission can be fully recapitulated by isolated physiology from each input. Finally, selective silencing by BoNT-C does not induce heterosynaptic structural or functional plasticity at the convergent input. Thus, BoNT-C establishes the first approach to accurately separate neurotransmission between tonic vs phasic neurons and defines heterosynaptic plasticity rules in a powerful model glutamatergic circuit.
All data generated or analyzed during this study are included in the manuscript and supporting files. In particular, full details of the data are included in Supplemental files 1 and 2.
Article and author information
National Institutes of Health (NS091546)
- Dion K Dickman
National Institutes of Health (NS111414)
- Dion K Dickman
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Chris Q Doe, Howard Hughes Medical Institute, University of Oregon, United States
- Received: February 16, 2022
- Preprint posted: February 17, 2022 (view preprint)
- Accepted: August 20, 2022
- Accepted Manuscript published: August 22, 2022 (version 1)
- Version of Record published: September 2, 2022 (version 2)
© 2022, Han et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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