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σ1 receptor ligands control a switch between passive and active threat responses


Humans and many animals show 'freezing' behavior in response to threatening stimuli. In humans, inappropriate threat responses are fundamental characteristics of several mental illnesses. To identify small molecules that modulate threat responses, we developed a high-throughput behavioral assay in zebrafish (Danio rerio) and evaluated 10,000 compounds for their effects on freezing behavior. We found three classes of compounds that switch the threat response from freezing to escape-like behavior. We then screened these for binding activity across 45 candidate targets. Using target profile clustering, we identified the sigma-1 (σ1) receptor as having a role in the mechanism of behavioral switching and confirmed that known σ1 ligands also disrupt freezing behavior. Furthermore, mutation of the gene encoding σ1 prevented the behavioral effect of escape-inducing compounds. One compound, which we call finazine, potently bound mammalian σ1 and altered threat-response behavior in mice. Thus, pharmacological and genetic interrogation of the freezing response revealed σ1 as a mediator of threat responses in vertebrates.

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Figure 1: High-throughput chemical screen for compounds that disrupt zebrafish freezing behavior.
Figure 2: Chemical structures of finazine, finoxetine and finopidil compounds.
Figure 3: Compound target profiling.
Figure 4: σ1 is a functional target of finazine.
Figure 5: Finazine has neuroactive effects in a mouse freezing assay.


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We thank C. Brady, J.J. Colund, I.T. Helenius, Y.N. Jin and A. Nath for helpful comments. Receptor binding profiles and Ki data were provided by the US National Institutes of Health (NIH) Psychoactive Drug Screening Program, contract HHSN-271-2008-025C. This work was supported by NIH grants T32 HL 007208 (A.J.R.), R01 MH 086867 (R.T.P.), R01 GM 088040 (R.T.P.) and U01 MH 105027 (D.K. and J.-R.J.Y.); the Charles and Ann Sanders MGH Research Scholar Award (R.T.P.); and the Harvard NeuroDiscovery Center.

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Authors and Affiliations



A.J.R. designed the experiments and performed the zebrafish behavioral and assays (including the screen), created the zebrafish mutants, analyzed the data and wrote the manuscript with R.T.P. S.P. and L.C. assisted A.J.R. with zebrafish assays. A.P.W.G. assisted with zebrafish mutagenesis. J.-R.J.Y. designed the zebrafish mutagenesis strategies. X.-P.H. performed the in vitro binding assays, which were designed by B.L.R. Y.W. performed the chemical synthesis and purity analyses. P.J.L. performed the mouse experiments and analyzed the data with B.J.C. B.J.C., D.K. and B.L.R. contributed reagents and to research design. All authors contributed to data interpretation and commented on the manuscript.

Corresponding author

Correspondence to Randall T Peterson.

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Competing interests

A.J.R., D.K., Y.W. and R.T.P. declare competing financial interests; they are inventors on a pending patent application, PCT/US2015/037755, covering the σ1 ligands described in this manuscript.

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Supplementary Text and Figures

Supplementary Results, Supplementary Figures 1–21, Supplementary Tables 1–3 and Supplementary Note 1. (PDF 6244 kb)

Strobe-induced freezing response in zebrafish larvae at low magnification. (AVI 40075 kb)


Strobe-induced freezing response in zebrafish larvae treated with tenfold increasing concentrations of finazine. (AVI 56946 kb)

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Rennekamp, A., Huang, XP., Wang, Y. et al. σ1 receptor ligands control a switch between passive and active threat responses. Nat Chem Biol 12, 552–558 (2016).

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