Abstract
The adult decerebrate mouse model (a mouse with the cerebrum removed) enables the study of sensory-motor integration and motor output from the spinal cord for several hours without compromising these functions with anesthesia. For example, the decerebrate mouse is ideal for examining locomotor behavior using intracellular recording approaches, which would not be possible using current anesthetized preparations. This protocol describes the steps required to achieve a low-blood-loss decerebration in the mouse and approaches for recording signals from spinal cord neurons with a focus on motoneurons. The protocol also describes an example application for the protocol: the evocation of spontaneous and actively driven stepping, including optimization of these behaviors in decerebrate mice. The time taken to prepare the animal and perform a decerebration takes ∼2 h, and the mice are viable for up to 3–8 h, which is ample time to perform most short-term procedures. These protocols can be modified for those interested in cardiovascular or respiratory function in addition to motor function and can be performed by trainees with some previous experience in animal surgery.
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Acknowledgements
This work was supported by Natural Sciences and Engineering Research Council grants to P.J.W. M.M. received funds from NIH NINDS R01NS077863. C.F.M. received funds from an EU FP7 Marie Curie Fellowship and project grants from the Lundbeck Foundation. C.F.M. acknowledges the technical assistance of L. Grøhndahl of the Meehan laboratory, the assistance of A. Hedegaard of the Meehan laboratory for the voltage clamp experiments, and advice regarding the voltage clamp and the voltage clamp external gain instrument from C.J. Heckman (Northwestern University). K.A.M. received a studentship from the Branch Out Neurological Foundation and the Hotchkiss Brain Institute. P.J.W. and K.A.M. acknowledge the technical assistance of A. Krajacic of the Whelan laboratory.
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C.F.M., K.A.M., M.M., and S.T.N. performed the experiments, analyzed the data, and prepared figures. P.J.W. wrote the paper and edited figures. C.F.M., K.A.M., M.M., S.T.N., and P.J.W. conceived of the experiments. C.F.M., K.A.M., S.T.N., M.M., and P.J.W. edited the manuscript.
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Integrated supplementary information
Supplementary Figure 1 Intramuscular hook electrode for recording electromyogram activity within muscles
(a) Rounded and sharpened curved spatula used for decerebration. (b) Custom made leg holder used to easily make a mineral oil bath for the hindlimb muscles and nerves. (c) One completed intramuscular EMG hook electrode using 3 stranded Teflon coated wire (A-M systems, cat No.793400) run through the lumen of a 23-gauge needle (B-D precisionGlide IM, cat No.305145). (d) Stripped 2-3 mm of Teflon coating from the end of the stainless steel wire. (e) 180o bend backwards, creating a hook. (f) Stainless steel wire hook pulled backwards to rest in the lowest part of the bevel of the lumen. a refers to Step 28 of procedure, b refers to Step 22. c-f refers to Step 32B.
Supplementary Figure 2 Increase in EMG tone indicating a bout of locomotion.
Increase in the amplitude of flexor and extensor EMG (tibialis anterior and gastrocnemius respectively), in the decerebrate preparation, indicating that a locomotor bout was imminent and that the treadmill should be turned on. Tibialis Anterior (TA), Gastrocnemius (Gast). All experiments should be performed in accordance with relevant guidelines and regulations. Local ethics committees have approved all procedures.
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Supplementary Figures and Text
Supplementary Figures 1 and 2. (PDF 352 kb)
Supplementary Video 1. Stepping behavior of a decerebrate mouse over a wheel.
This video shows expected decerebrate walking activity and illustrates the outcome of intrathecal application of 5-HT. (MP4 5164 kb)
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Meehan, C., Mayr, K., Manuel, M. et al. Decerebrate mouse model for studies of the spinal cord circuits. Nat Protoc 12, 732–747 (2017). https://doi.org/10.1038/nprot.2017.001
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DOI: https://doi.org/10.1038/nprot.2017.001
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