bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2022.10.04.510858

Serotonergic Modulation of Spinal Circuitry Restores Motor Function after Chronic Spinal Cord Injury

Walvekar, S.·Robinson, R. B.·Chadwick, H. M.·Burch, R. M.·Ding, H.·Perlmutter, S. I.·Moorjani, S.
View original source ↗Export metadata ↓

Abstract

Electrical stimulation of the nervous system has been employed to enhance the recovery of motor function produced by use-dependent rehabilitation, which is the current gold standard of treatment, following spinal cord injury. However, the therapeutic effects almost always rely on the sustained activation of muscles or neurons, making the benefits largely contingent on continued delivery of stimulation. In the present study, we describe a neuromodulatory intervention that combined intraspinal delivery of serotonergic agonists with use-dependent rehabilitation to restore motor function after a chronic moderate-to-severe cervical contusion in rats that produces impairments in upper-limb movements and dexterity. We show that targeted delivery of quipazine, a broad-spectrum serotonergic agonist, caudal to the lesion increased the effectiveness of physical rehabilitation, leading to substantially improved motor-recovery outcomes in severely-injured, but not moderately-injured, animals. Delivery of quipazine significantly augmented recovery of skilled reach and grasp movements after a severe injury, but moderately-injured animals received no additional benefit from quipazine over physical rehabilitation alone. This difference was perhaps due to a greater loss of serotonin after a severe injury and a resulting environment in which exogenously-applied serotonin can improve circuit function. Our experiments highlight an important role for serotonin in restoration of motor function that is dependent on the severity of the spinal cord injury. They also allude to a potential role for residual serotonin as a biomarker of injury severity. Remarkably, quipazine-mediated behavioral improvements persisted for weeks after termination of neuromodulator delivery, signaling repair of severely-damaged adult spinal circuitry that drives lasting motor recovery. Significance StatementWe describe a neuromodulatory intervention that combined intraspinal delivery of serotonergic agonists with use-dependent physical rehabilitation, which is the current standard of treatment, to promote motor recovery after a chronic moderate-to-severe spinal-contusion injury. Our results show that targeted delivery of serotonergic agonists caudal to the lesion increased the effectiveness of use-dependent rehabilitation, leading to substantially improved motor-recovery outcomes in severely-injured, but not moderately-injured, animals. Notably, therapeutic gains persisted for weeks after termination of neuromodulator delivery--a finding that is both unique and clinically relevant--signaling plasticity induction and repair in chronically-damaged adult spinal circuitry. Our experiments provide important insights into serotonergic modulation of spinal circuitry and highlight a potential role for residual serotonin as a neurochemical biomarker of injury severity.

Explore related subjects

neurosciencePreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Walvekar, S., Robinson, R. B., Chadwick, H. M., Burch, R. M., Ding, H., Perlmutter, S. I., Moorjani, S.. 2022-10-07. Serotonergic Modulation of Spinal Circuitry Restores Motor Function after Chronic Spinal Cord Injury. https://doi.org/10.1101/2022.10.04.510858

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

The Unreasonable Effectiveness of Cell Types in Describing Neuronal Physiological Features

Single-cell RNA sequencing (scRNA-seq) captures detailed gene expression profiles at scale, while patch-clamp recordings measure intrinsic neuronal electrophysiological properties. Modeling the relations between these two modalities remains a challenge. Here, we compare how well electrophysiological features can be predicted by traditional transcriptomic cell type classification, representations derived from a foundational model (scGPT) pretrained on large-scale scRNA-seq datasets, ion channel-coding genes, and highly variable genes. Using paired transcriptomic and electrophysiological patch-sequencing data from 495 human neurons from neurosurgical tissue, we find that cluster-level cell type representations consistently outperform highly variable gene selection, ion channel gene selection, and context-enriched scGPT embeddings. Notably, performance varies across model architectures and initializations, and the best results are obtained by combining the outputs of separate cell type and scGPT-based models. Together, these findings suggest that traditional discrete cellular classification is highly effective in predicting physiological features. For maximum performance it can be complemented by pretrained transformer models.

neuroscience↗
bioRxiv2026

A nonlinear inhibition pathway underlying cortical responses to tuned holographic optogenetic perturbations

Optogenetics enables causal manipulation of cortical activity. Perturbation responses can be counterintuitive due to network interactions, making theory essential for predicting them. Existing approaches often rely on linear approximations, which fail for many biologically relevant perturbations. Here we develop a nonlinear theory of responses to holographic perturbations in cell-type-specific recurrent networks with structured connectivity. We fit a nonlinear model to mouse V1 data, which shows cotuned-ensemble suppression: perturbing spatially clustered neurons with similar preferred orientations yields markedly stronger short-range suppression than perturbing untuned ensembles. We show that cotuned-ensemble suppression arises from a feature-tuned, nonlinear inhibition pathway implicating somatostatin-positive (SST) interneurons. The theory predicts that cotuned ensembles suppress parvalbumin-positive (PV) neurons but facilitate SST neurons, and links the degree of cotuned-ensemble suppression or facilitation to the variance of the SST response. This framework identifies mechanisms by which nonlinear inhibition sculpts cortical dynamics and establishes a predictive basis for targeted optogenetic interventions.

neuroscience↗
bioRxiv2026

Proteomic signatures of APOE ε4 across human tissues and cell types in Alzheimers disease

The apolipoprotein E {varepsilon}4 (APOE {varepsilon}4) allele is the strongest genetic risk factor for late-onset Alzheimers disease (AD). However, the underlying molecular mechanisms remain unclear. This study included 1691 participants from the Religious Orders Study and Rush Memory and Aging Project (ROSMAP), 1226 participants from the Accelerating Medicines Partnership - Alzheimers Disease (AMP-AD) Diverse Cohorts Study, and 735 participants from the Alzheimers Disease Neuroimaging Initiative (ADNI). To characterise APOE {varepsilon}4 molecular effects, we analysed proteomic data from plasma, cerebrospinal fluid (CSF), and induced pluripotent stem cell (iPSC)-derived astrocytes and neurons, as well as transcriptomic and proteomic data from multiple brain regions. The association of APOE {varepsilon}4 with AD neuropathology was also examined. APOE {varepsilon}4 carriers shared a plasma proteomic signature enriched for immune processes, irrespective of AD diagnosis. A machine learning classifier trained on this signature discriminated APOE {varepsilon}4 carriers from non-carriers in an independent cohort using CSF proteomics. APOE {varepsilon}4 carriage was associated with higher Braak stages and Consortium to Establish a Registry for Alzheimers Disease (CERAD) score. However, only limited APOE {varepsilon}4-associated transcriptomic and proteomic changes were observed in bulk brain tissue, with poor cross-layer concordance. Proteomic analyses of iPSC-derived astrocytes and neurons further revealed cell-type-specific APOE {varepsilon}4-associated changes. APOE {varepsilon}4 is associated with a consistent proteomic signature across plasma and CSF. Its molecular effects in the brain differ across cell types, brain regions and molecular layers. These findings support the need for cell-type-resolved multi-omic studies to elucidate how APOE {varepsilon}4 confers AD risk.

neuroscience↗