Abstract
Neurological disorders, including spinal cord injury, result in hemodynamic instability due to the disruption of supraspinal projections to the sympathetic circuits located in the spinal cord. We recently developed a preclinical model that allows the identification of the topology and dynamics through which sympathetic circuits modulate hemodynamics, supporting the development of a neuroprosthetic baroreflex that precisely controls blood pressure in rats, monkeys and humans with spinal cord injuries. Here, we describe the continuous monitoring of arterial blood pressure and sympathetic nerve activity over several months in preclinical models of chronic neurological disorders using commercially available telemetry technologies, as well as optogenetic and neuronal tract-tracing procedures specifically adapted to the sympathetic circuitry. Using a blueprint to construct a negative-pressure chamber, the approach enables the reproduction, in rats, of well-controlled and reproducible episodes of hypotension-mimicking orthostatic challenges already used in humans. Blood pressure variations can thus be directly induced and linked to the molecular, functional and anatomical properties of specific neurons in the brainstem, spinal cord and ganglia. Each procedure can be completed in under 2 h, while the construction of the negative-pressure chamber requires up to 1 week. With training, individuals with a basic understanding of cardiovascular physiology, engineering or neuroscience can collect longitudinal recordings of hemodynamics and sympathetic nerve activity over several months.
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Data availability
The datasets discussed in this protocol are available from Zenodo: https://doi.org/10.5281/zenodo.5227224.
Code availability
Aima is available from GitHub at https://github.com/neurorestore/Aima and as Supplementary Software 1.
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Acknowledgements
The present work was supported by a Consolidator Grant from the European Research Council (ERC-2015-CoG HOW2WALKAGAIN 682999), the Swiss National Science Foundation (subsides 310030_130850, CRSII5_183519, BSCGI0 1578000), Compute Canada, the Natural Sciences and Engineering Research Council, the Canadian Institutes of Health Research, Banting Fellowship, Alberta Innovates Health Solutions, Campus Alberta Neuroscience, the Libin Cardiovascular Institute, the Hotchkiss Brain Institute, PRAXIS, International Foundation for Research in Paraplegia, McCaig Institute for Bone and Joint Health. J.W.S. is supported by a CIHR Banting postdoctoral fellowship and a Marie Skłodowska-Curie individual fellowship (no. 842578). J.E.S. is supported by a CIHR Canada Graduate Scholarships - Doctoral Program scholarship, a BRAIN CREATE graduate scholarship, an Eyes High doctoral recruitment scholarship, and a Branch Out Neurological Foundation scholarship. We are grateful to Bernard Schneider and Theofanis Karayannis for providing viral vectors; Laura Batti and Ivana Gantar from the Advanced Lightsheet Imaging Center (ALICe) at the Wyss Center for Bio and Neuroengineering, Geneva; and Fabien Moreillon from Hepia, Campus Biotech Geneva.
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J.W.S., J.E.S., R.H. and L.M. designed and developed the surgical procedures. J.W.S., S.A. and M.G. and A.A.P. designed and developed the assessment equipment and procedures. J.W.S. and M.G. designed and developed Aima. J.W.S., V.P.P. and A.A.P. designed the lower-body negative-pressure chamber. Q.B. developed the histological and imaging procedures. A.A.P. and G.C. supervised the work. J.E.S., R.H., J.W.S., Q.B., A.A.P. and G.C. wrote the manuscript. All authors edited the manuscript.
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G.C., A.A.P. and J.W.S. have filed several patents in relation to the present work. G.C. and A.A.P. are consultants of ONWARD medical. G.C. and A.A.P are shareholders of ONWARD, a company with direct relationships with the presented work.
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Squair, J. W. et al. Nature 590, 308–314 (2021): https://doi.org/10.1038/s41586-020-03180-w
Asboth, L. et al. Nat. Neurosci. 21, 576–588 (2018): https://doi.org/10.1038/s41593-018-0093-5
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Code blocks to reproduce each procedure in the protocol.
Supplementary Software 1
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Soriano, J.E., Hudelle, R., Squair, J.W. et al. Longitudinal interrogation of sympathetic neural circuits and hemodynamics in preclinical models. Nat Protoc 18, 340–373 (2023). https://doi.org/10.1038/s41596-022-00764-w
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DOI: https://doi.org/10.1038/s41596-022-00764-w
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