# Stimulation of Cervical Excitatory Interneurons to Restore Breathing After Chronic Cervical Spinal Cord Injury

> **NIH VA I01** · CLEMENT J. ZABLOCKI VA MEDICAL CENTER · 2022 · —

## Abstract

Dysfunctional breathing is a significant cause of morbidity and mortality after cervical SCI (cSCI). The ability to
restore breathing in the chronic phase after cervical SCI (cSCI) is an overwhelming yet important goal. The
diaphragm, the major inspiratory muscle, is innervated by phrenic motoneurons (PMNs) located in the cervical
spinal cord (C3-C5). Cervical interneurons synapse onto PMNs and discharge in synchrony with phrenic inspir-
atory output and modulate breathing. Premotor neurons within the rostral ventral respiratory group of neurons
(rVRG) in the brainstem provide the main inspiratory drive to the spinal respiratory circuitry. Cervical spinal cord
injury (SCI) disrupts the communication between rVRG and the spinal respiratory circuitry resulting in significant
respiratory compromise. We recently demonstrated that pharmacogenetic stimulation of cervical excitatory in-
terneurons (eINs) immediately after cSCI rescues breathing in mice; however, it is not known if this strategy will
be effective in improving breathing in the chronic phase of cSCI. At the chronic stage, the respiratory network is
known to undergo significant modifications. Moreover, our previous work in non-traumatic compressive injury to
the cervical spinal cord demonstrated that cervical eINs play an integral role in promoting plasticity and main-
taining ventilation despite a significant loss of PMNs. Given that cervical eINs integrate into the respiratory net-
work, and they are necessary for the spontaneous respiratory recovery, they emerge as critical therapeutic tar-
gets for respiratory recovery in the chronic phase after traumatic cSCI. We hypothesize that providing selec-
tive excitatory input to surviving PMNs at the late stage of cSCI will enhance PMNs output and respiratory
recovery. The first objective of this proposal aims to gain more significant insights into the status of the respira-
tory neural network after chronic cSCI. The second objective of this proposal will examine a novel treatment
strategy involving selective stimulation of cervical eINs to promote respiratory recovery in the chronic phase after
cSCI.
In aim 1, we will assess the survival of PMNs following C2 hemisection injury (C2Hx) using the monosynaptic
retrograde tracer Cholera Toxin Subunit B to specifically track the PMNs. In the second part of Aim 1, we will
simultaneously map the input-output connectivity of the cervical respiratory elements, the PMNs and the
prephrenic cervical eINs, in the naïve-uninjured state and after cSCI. In Aim 2, we will selectively stimulate the
cervical eINs in the region of the phrenic nuclei after chronic cSCI using the DREADD technology. This technique
has innovative applications due to its ability to activate or silence neuronal populations non-invasively. The effect
of stimulating cervical eINs on promoting respiratory recovery after chronic cSCI will be assessed using electro-
myography and whole-body plethysmography. The expected outcomes of the pro...

## Key facts

- **NIH application ID:** 10360818
- **Project number:** 1I01BX005287-01A2
- **Recipient organization:** CLEMENT J. ZABLOCKI VA MEDICAL CENTER
- **Principal Investigator:** Shekar N. Kurpad
- **Activity code:** I01 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2022
- **Award amount:** —
- **Award type:** 1
- **Project period:** 2022-01-01 → 2025-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10360818

## Citation

> US National Institutes of Health, RePORTER application 10360818, Stimulation of Cervical Excitatory Interneurons to Restore Breathing After Chronic Cervical Spinal Cord Injury (1I01BX005287-01A2). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10360818. Licensed CC0.

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