The dI3 population of spinal cord interneurons (INs) is a group of excitatory INs that receive varied sensory afferent input and project to ipsilateral motoneurons. Prior experiments have discovered that the permanent silencing of dI3 INs has a minimal impact on locomotor function in intact animals, but substantially interferes with locomotor rehabilitation/recovery after spinal cord injury (SCI). To gain insight into how dI3 INs are involved with locomotor function and recovery, the inhibitory DREADD receptor (hM4Di) was expressed in dI3 INs using a hybrid line of transgenic mice (Isl1-Cre:Vglut2-Flp x FlexloxFlexFRT-hM4Di). Consistent with prior experiments, transient inhibition of hM4Di-expressing dI3 neurons with the DREADD agonist JHU37160 (0.5mg/kg) did not significantly impact locomotor function in intact animals. However, in T9-T10 SCI mice, transient silencing of dI3 INs resulted in a significant loss of flexor motor tone, demonstrated by a significant increase in the resting ankle joint angle (+43.9° ± 11.6°, n=7, t-test, p=0.0065). This coincided with decreased stepping and the qualitative appearance of hindlimb flaccidity during the treadmill locomotor task. Based on these results, dI3 INs appear to adopt a more significant role in hindlimb function after SCI, specifically the maintenance of basal motor tone in the absence of supraspinal input. Given that SCI patients often experience both hypotonia and spasticity (increased motor tone), these findings provide the impetus for targeting dI3 INs to modulate motor tone below the level of the lesion.

dI3 interneurons maintain hindlimb motor tone in mice following spinal cord injury

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PS-2-D -  Sensory and Motor Systems

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Colleagues and Friends:

I am very happy to welcome you to the 14th annual Canadian Neuroscience Meeting, and to the first virtual edition of our meeting. I want to highlight the important work the CAN meeting chair, **Roger Thompson** and co-chair, **Alyson Fournier**, did to put together the great program we are offering this year. Moving to a virtual format required a complete re-design of the program, and both Roger and Alyson did a splendid job in providing us with an appealing and well adapted program for our first virtual event. I wish to thank them for this very important effort.

Highlights of this year’s scientific meeting include invited speakers **Michael Hausser, Franck Polleux, Gwyneth Card, Magdalena Götz**and Brain Prize winner **Huda Zoghbi**. Plenary and parallel symposia, proposed by our members complete our diverse [scientific program.](https://can-acn.org/meeting-2021/program-2021/)

The 2021 Advocacy session, chaired and organized by CAN advocacy committee chair **Karun Singh**, will feature a special lecture and question period with Member of Parliament and past Science Minister **Kirsty Duncan**. This will be followed by a short overview of CAN’s advocacy activities over the last year. We invite you to participate in this session for insight from Dr. Duncan on the workings of Parliament Hill, and to learn more about what CAN has been doing to promote neuroscience research in Canada.

We are also excited to host **Lisa Willis** in the Equity Diversity and Inclusion session, organized by EDI committee chair **Jibran Khokhar**.

A special highlight of our meeting will be the lectures by award-winning young neuroscientists. We are please to host the CAN 2020 Young Investigator Award winner **Mihaela Iordanova**, and CAN 2021 Young Investigator Award winners **Aaron Phillips** and **Tabrez Siddiqui**. Highlights will also include presentation by the top three winners of the CAN-CIHR-INMHA Brain Star Award winners, **Claire Gizowski, Nuria Daviu Abant** and **Lukas Tamayo-Orrego**.

Independently organized satellite symposia complement and complete this exciting program, check them out here: https://can-acn.org/meeting-2021/2021-satellite-symposia/

Some of the most engaging sessions are always the poster sessions featuring the work of our trainees, so make sure to log in to Gather Town during the poster sessions to chat with the presenters.
We hope you enjoy this program, and look forward to welcoming you, virtually.

Shernaz Bamji

President of the Canadian Association for Neuroscience

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dI3 interneurons maintain hindlimb motor tone in mice following spinal cord injury

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