Experimental Neurology

BackgroundThe entopeduncular nucleus (EP), corresponding to the human globus pallidus internal segment, is a basal ganglia output nucleus, and plays a critical role in motor control. However, the impact of EP damage on skilled motor function and the relationship between its damage in stroke, such as internal capsule hemorrhage (ICH), and motor dysfunction remains unclear. This study aimed to clarify whether EP damage causes motor dysfunction in two disease models. MethodsEP-related motor dysfunction was investigated by inducing localized unilateral EP damage in Long-Evans rats using a stereotactic kainic acid (KA) injection. Motor function was assessed using a single-pellet reaching task pre-injection and on postoperative days 2, 7, 14, 21, and 28. Immunohistochemical staining for NeuN, somatostatin (SST), and parvalbumin was conducted to quantify damage and its correlation with motor outcomes. In addition, unilateral ICH was induced via stereotactic injection of collagenase type IV, which dissolves the vascular basement membrane, into the internal capsule (IC) of Long-Evans rats. Injury sites were classified into the IC, dorsomedial region from the IC, ventral lateral region from the IC, and EP, and their volumes were measured. Measured volumes were analyzed for correlations with motor function assessments. ResultsKA-induced EP damage significantly reduced reaching success rates on postoperative day 2 compared to those in the control group (p<0.05). Immunohistochemical analysis showed that reaching success rates on day 28 positively correlated with the numbers of remaining NeuN-positive and SST-positive neurons (p<0.05). In the ICH experiment, all rats significantly reduced the success rate of the reaching task to 0% on day 2, and the success rate on day 28 correlated positively with the remaining EP volume, but not with total lesion volume. ConclusionsEP damage was strongly associated with motor impairments, highlighting its critical role in motor control and recovery.

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.

Neurogenic bladder dysfunction causes urological complications and reduces the quality of life in persons with spinal cord injury (SCI). Glutamatergic signaling via AMPA receptors is fundamentally important to the neural circuits controlling bladder voiding. Ampakines are positive allosteric modulators of AMPA receptors that can enhance the function of glutamatergic neural circuits after SCI. We hypothesized that ampakines can acutely stimulate bladder voiding that has been impaired due to thoracic contusion SCI. Adult female Sprague Dawley rats received a unilateral contusion of the T9 spinal cord (n=10). Bladder function (cystometry) and coordination with the external urethral sphincter (EUS) were assessed five days post-SCI under urethane anesthesia. Data were compared to responses in spinal intact rats (n=8). The "low impact" ampakine CX1739 (5, 10, or 15 mg/kg) or vehicle (HPCD) was administered intravenously. The HPCD vehicle had no discernable impact on voiding. In contrast, following CX1739, the pressure threshold for inducing bladder contraction, voided volume, and the interval between bladder contractions were significantly reduced. These responses occurred in a dose-dependent manner. We conclude that modulating AMPA receptor function using ampakines can rapidly improve bladder voiding capability at sub-acute time points following contusion SCI. These results may provide a new and translatable method for therapeutic targeting of bladder dysfunction acutely after SCI.

Spinal cord injury (SCI) disrupts corticospinal tract (CST) connectivity and impairs skilled voluntary movement. However, most human SCIs are anatomically incomplete, allowing spared CST pathways to engage in rehabilitation-mediated plasticity to promote functional recovery. How voluntary rehabilitation engages and reorganizes the supraspinal targets of the intact CST remains incompletely understood. Here, we combined unilateral pyramidotomy (uPyX) in male and female mice with continuous voluntary complex-wheel running to test whether fine motor-dependent rehabilitation drives supraspinal CST plasticity. uPyX mice rapidly resumed wheel running after a transient deficit. In contrast to lesion-only controls, rehabilitation significantly improved skilled forelimb performance on the horizontal ladder rung task. Immunohistochemical c-Fos labeling confirmed that complex-wheel running robustly activated the intact forelimb CST in motor cortex. Whole-brain CST projection mapping using intersectional viral vector tracing revealed targeted supraspinal reorganization localized to medullary motor nuclei. Three nuclei - the lateral paragigantocellular reticular nucleus (LPGi), gigantocellular reticular nucleus, alpha part (GiA), and ventral medullary reticular nucleus (MdV) - exhibited significant lesion- and/or rehabilitation-induced increases in CST innervation. Rehabilitation-driven CST sprouting correlated with regional c-Fos activation, indicating activity-dependent remodeling. Notably, CST projection density in the MdV, critical for skilled forelimb control, correlated with functional recovery. These findings identify a set of spinally-projecting medullary nuclei as key sites of rehabilitation-induced CST plasticity and highlight the MdV as a potential mediator of restored motor function. This work defines how voluntary rehabilitation reorganizes spared corticospinal pathways and provides targets for optimizing activity-based interventions after SCI. Significance StatementEffective rehabilitation after spinal cord injury (SCI) must harness the plasticity of spared motor pathways, yet the supraspinal circuits that support rehabilitation-mediated recovery remain unknown. Using a model that preserves voluntary motor engagement, we show that continuous fine motor-dependent rehabilitation activates intact corticospinal neurons and drives highly specific remodeling of their supraspinal terminals. Rehabilitation selectively strengthens CST inputs to motor regions of the medulla, particularly the ventral medullary reticular nucleus (MdV), and CST plasticity within this region predicts enhanced behavioral recovery. These findings highlight the MdV as a central locus by which rehabilitation re-establishes descending control of the impaired limb, providing mechanistic insight to guide targeted, circuit-based rehabilitation therapies for incomplete SCI.

The circadian rhythms of gene expression drive diurnal oscillations of physiological processes that determine the acute injury response including immunity, inflammation and hemostasis. While outcomes of various acute injuries are affected by the time of day at which the original insult occurred, such diurnal influences on recovery after spinal cord injury (SCI) are unknown. We report that several key regulators of circadian gene expression are differentially expressed in uninjured spinal cord tissue of naive mice at Zeitgeber time 1 (ZT1) or ZT12, where ZT0 or ZT12 are times when lights are turned on or off, respectively. However, mice that received moderate, T9 contusive SCI at ZT0 or ZT12 showed similar recovery of locomotion as determined using the ladder walking test and the Basso mouse scale (BMS) over a 6 week post-injury period. Consistent with those findings, terminal histological analysis revealed no significant differences in white matter sparing at the injury epicenter. Therefore, locomotor recovery after thoracic contusive SCI is not affected by the time of day at which the neurotrauma occurred at least when comparing the beginning to the end of the mouse active period.

In response to traumatic brain injury (TBI), the brain increases its generation of new neurons (neurogenesis) within the hippocampus, a brain region critical for learning and memory. Because neurogenesis plays important roles in learning and memory, post-traumatic neurogenesis may represent an adaptive response contributing to cognitive recovery. In contrast to increases in neurogenesis acutely after injury, levels of neurogenesis become impaired long after TBI. And although chronic deficits in neurogenesis after TBI have been reported by multiple groups, it is unknown whether the hippocampus remains capable of eliciting another neurogenic response to a repeated injury. To address this lack of knowledge, we used a closed head injury model that reflects a concussive-like injury or a mild TBI (mTBI) and assessed levels of neurogenesis in male and female adult mice. Mice received one or two mTBI or sham treatments 3 weeks apart. Compared to mice with a single mTBI, proliferation and neurogenesis were blunted in mice that received a second mTBI. This impaired response was unlikely due to a short recovery time between the two mTBIs as the proliferative response to a second mTBI was also impaired when two months were allowed between injuries. We further found that proliferation was impaired in the radial-glia like cells despite an intact pool. The mice that received two mTBIs also had a blunted intensity in their GFAP staining. In contrast to reports of aberrant post-TBI neurogenesis, we found that the neurons born after mTBI had normal dendritic branches. Lastly, we found that impairments in the inability to mount a neurogenic response after a second mTBI were associated with deficits in neurogenesisstrategy flexibility in the reversal water maze task. Our data suggests that a loss in the neurogenic response could in part contribute to worse cognitive recovery after a repeated concussion. These data may expose a novel target to help improve long-term cognitive outcome following repeated brain injury.

Traumatic brain injury (TBI) is a major global health concern, affecting more than 40 million people annually. While most cases are mild and present with light symptoms, repeated mild injuries can result in delayed brain pathologies, including cognitive decline, neuropsychiatric complications, and post-traumatic epilepsy (PTE). PTE refers to recurring, unprovoked seizures occurring at least one week after TBI. While the link between moderate to severe TBI and PTE is well established, the epileptogenesis after repetitive mild TBI (rmTBI) is seldom studied. Currently, there are no biomarkers to identify those at risk of developing PTE, and its diagnosis is challenging. Here, we used a rat model to study PTE following rmTBI and assessed human EEG data to identify potential biomarkers for PTE. We employed a closed head TBI model to induce rmTBI, and recorded brain activity using electrocorticography (ECoG) between 2- and 6-months post-injury. Behavioral assessments and post-mortem analysis were also conducted. In humans, we analyzed EEG recordings from the Temple University database to investigate the potential of EEG-derived features for diagnosing PTE. At 6 months post injury, 70% of rmTBI animals developed PTE, compared to 22% in the control group (P=0.01). While neurological assessments following injury did not predict PTE, paroxysmal slow wave events (PSWEs) were found to be a reliable biomarker for PTE prediction. In humans, the percentage time in PSWEs was significantly elevated in PTE patients with epileptiform activity. In conclusion, we suggest PSWEs as a non-invasive, cost-effective biomarker for PTE in rodents and human patients.

Parkinsons disease (PD) is characterized by the degeneration of dopaminergic (DA) neurons in the substantia nigra pars compacta, leading to dopamine depletion in the striatum and the hallmark motor symptoms of the disease. However, non-motor deficits, particularly sensory symptoms, often precede motor manifestations, offering a potential early diagnostic window. The impact of non-motor deficits on sensation behavior and the underlying mechanisms remain poorly understood. In this study, we examined changes in tactile sensation within a parkinsonian state by employing a mouse model of PD induced by 6-hydroxydopamine (6-OHDA) to deplete striatal DA. Leveraging the conserved mouse whisker system as a model for tactile-sensory stimulation, we conducted psychophysical experiments to assess sensory-driven behavioral performance during a tactile detection task in both the healthy and PD-like state. Our findings reveal a range of deficits across subjects following 6-OHDA lesion, including DA loss, motor asymmetry, weight loss, and varying levels of altered tactile sensation behavior. Behavioral changes ranged from no impairments in minor cases to isolated sensory-behavioral deficits in moderate cases and severe motor dysfunction in advanced stages. These results underscore the complex relationship between DA imbalance and sensory-motor processing, emphasizing the need for precise and multifaceted behavioral measurements to accurately capture the diverse manifestations of PD. SIGNIFICANCE STATEMENTThis study explores sensory-motor aspects of Parkinsons disease using a 6-OHDA mouse model. Leveraging the mouse whisker system, we reveal diverse deficits in tactile sensation behavior due to dopamine depletion. Our findings emphasize the importance of sensory assessments in understanding the diverse spectrum of PD symptoms.

Pathogenic variants of the sodium-activated potassium channel KNa1.1, have been reported in multiple epileptic disorders. However, whether and how KNa1.1 channel is involved in epileptogenesis after traumatic brain injury (TBI) remains unknown. Firstly, we used behavioral monitoring and EEG recording to examine physiological property, spontaneous seizure activity, and seizure susceptibility after TBI. We explored the changes of KNa1.1 channel following TBI, including changes of subcellular distribution and expression pattern. Meanwhile, we performed patch-clamp recording to detect the neuronal excitability. Furthermore, we built TBI model using kcnt1-/- mice and compared seizure activity with those on wild- type mice. We found severity-dependent seizure susceptibility in different degree of injured mice. Meanwhile, increased neuronal expression of KNa1.1 channel, especially in inhibitory neurons, around the lesion was also observed following TBI with increased neuronal excitability including reduced firing rate of interneurons and imbalanced excitation and inhibition (E/I). Although the maximum frequency of action potential of kcnt1-/- neurons was increased, kcnt1-/- mice displayed decreased seizure susceptibility to the pentylenetetrazole (PTZ) after TBI. Taken together, this study suggests that pathologically enhanced expression and abnormally distributed KNa1.1 channel after TBI contribute to disputed E/I and seizure susceptibility, which might provide a potential therapeutic target on the epileptogenesis after TBI.

The purpose of this study was to determine if spike-triggered intraspinal microstimulation (ISMS) results in improved motor performance in an ambulatory rat model of spinal cord injury (SCI). Experiments were carried out in adult male Sprague Dawley rats with 175 kdyn moderate T8 contusion injury. Rats were randomly assigned to one of two groups: Control or Activity Dependent Stimulation (ADS) therapy. Four weeks post-SCI, all rats were implanted with a recording electrode in the left hindlimb motor cortex and a fine-wire, custom-made stimulating electrode in the contralateral lumbar spinal cord. Intracortical and intraspinal microstimulation were used to find sites of similar hip representation areas, which were paired together for ADS therapy. In the ADS therapy group, spike-stimulus conditioning was administered for 4 hours/day, 4 days/week, for 4 weeks via a tethered cable in a testing chamber. During therapy sessions, single-unit spikes were discriminated in real time in the hindlimb motor cortex and used to trigger stimulation in the spinal cord ventral horn. The optimal stimulus intensity (50% ISMS movement threshold) and spike-stimulus delay (10ms) determined in preliminary anesthetized preparations were used during ADS. Control rats were similarly implanted with electrodes but did not receive stimulation therapy. Motor performances of each rat were evaluated before SCI contusion, once a week post-SCI for four weeks (prior to electrode implantation), and once a week post-conditioning for four weeks. Behavioral testing included BBB scoring, Ledged Beam walking, Horizontal Ladder walking, treadmill kinematics via the DigiGait and TreadScan system, and open field walking using OptiTrack kinematic analysis. BBB scores were significantly improved in ADS rats compared to Control rats after 1 week of therapy. In the ADS therapy rats, BBB scores were significantly improved after two weeks of ADS therapy when compared to pre-therapy. Foot fault scores on the Horizontal Ladder were significantly lower in ADS rats compared to pre-therapy ADS and Control rats after 1 week of therapy and returned to pre-injury measures after three weeks of ADS therapy. The Ledged Beam test and kinematic analysis using the DigiGait and TreadScan system showed deficits after SCI in both ADS and Control rats but there were no significant differences between groups after 4 weeks of ADS therapy. These results show that activity dependent stimulation after spinal cord injury using spike-triggered ISMS enhances behavioral recovery of locomotor function as measured by the BBB score and the Horizontal Ladder task.

The brain-spinal cord axis generates movement by assembling motor primitives into coordinated sequences. Spinal cord injury (SCI) disrupts this neuroaxis, impairing not only locomotion, but the full repertoire of behavior. Traditional scales for quantifying recovery collapse this complexity into predefined locomotor-focused criteria that obscure heterogeneity in recovery. To quantify the full behavioral repertoire following SCI, we adapted motion sequencing (MoSeq) to identify sub-second behavioral "syllables" and capture their usage and sequential organization without predefined features. We identified biomechanically distinct variants within syllable classes that are shared across injury severities and found that recovery is jointly structured by injury severity and individual mouse identity. Changes in sequences, however, unfold along a conserved temporal trajectory. By compressing behavior into a single metric, we uncovered clusters of coevolving locomotor and non-locomotor behaviors. These results frame SCI recovery with repertoire-level changes, where adaptive strategies emerge from constrained access to motor primitives and their sequences.

Spinal cord injury (SCI) is a devastating condition characterized by impaired motor and sensory function, as well as internal organ pathology and dysfunction. This internal organ dysfunction, particularly gastrointestinal (GI) complications, and neurogenic bowel, can reduce the quality of life of individuals with an SCI and potentially hinder their recovery. The gut microbiome impacts various central nervous system functions and has been linked to a number of health and disease states. An imbalance of the gut microbiome, i.e., gut dysbiosis, contributes to neurological disease and may influence recovery and repair processes after SCI. Here we examine the impact of high cervical SCI on the gut microbiome and find that transient gut dysbiosis with persistent gut pathology develops after SCI. Importantly, probiotic treatment improves gut health and respiratory motor function measured through whole-body plethysmography. Concurrent with these improvements was a systemic decrease in the cytokine tumor necrosis factor-alpha and an increase in neurite sprouting and regenerative potential of neurons. Collectively, these data reveal the gut microbiome as an important therapeutic target to improve visceral organ health and respiratory motor recovery after SCI. Research HighlightsO_LICervical spinal cord injury (SCI) causes transient gut dysbiosis and persistent gastrointestinal (GI) pathology. C_LIO_LITreatment with probiotics after SCI leads to a healthier GI tract and improved respiratory motor recovery. C_LIO_LIProbiotic treatment decreases systemic tumor necrosis factor-alpha and increases the potential for sprouting and regeneration of neurons after SCI. C_LIO_LIThe gut microbiome is a valid target to improve motor function and secondary visceral health after SCI. C_LI

Following a spinal cord injury (SCI), chondroitin sulfate proteoglycans (CSPGs) are up-regulated at the glial scar inhibiting neuroregeneration. Under normal physiological condition, CSPGs interact with hyaluronan (HA) and other extracellular matrix on neuronal surface forming a macromolecular structure called perineuronal nets (PNNs) which regulate neuroplasticity. 4-methylumbelliferone (4-MU) has been used previously to down-regulate HA synthesis but not been tested in SCI. In this study, we have evaluated the effect of 4-MU, an inhibitor of HA, in a chronic contusion model of SCI in rats. At a dose of 1.2 g/kg/day of 4-MU, we observed not only the reduction of HA in the uninjured spinal cords after 60 days of 4-MU administration, but also a down-regulation of CS glycosaminoglycans (CS-GAGs). In order to assess the effect of 4-MU in chronic SCI, rats with T8 spinal contusion injury were fed with 4-MU or placebo for 8 weeks in combination with daily treadmill rehabilitation for 16 weeks to promote neuroplasticity. 4-MU treatment promoted significant sprouting of 5-hydroxytryptamine (5-HT) positive fibres into ventral horns and reduced the HA synthesis by astrocytes around the lesion site. While 4-MU reduced astrogliosis in chronic stage of SCI, the current dose was not sufficient to down-regulate the increased production of CS-GAGs or behavioural performance. Together, these data suggest that oral treatment with 4-MU is able to induce anatomical plasticity but further adjustment on the dosage will be required to benefit functional recovery after SCI.

Spinal cord injury (SCI) triggers secondary pathophysiological cascades, including glutamate excitotoxicity, that result in neuronal loss and impair functional recovery. We have previously shown that lysophosphatidylethanolamine (LPE), a lysophospholipid, promotes neurite outgrowth and protects against glutamate excitotoxicity in cultured cortical neurons. However, whether these effects extend to spinal cord neurons and occur in vivo has remained unclear. In this study, we compared the effects of different LPE species: myristoyl-LPE (14:0 LPE), palmitoyl-LPE (16:0 LPE), stearoyl-LPE (18:0 LPE), and oleoyl-LPE (18:1 LPE) in cultured spinal commissural neurons, and evaluated their effects in vivo using a mouse model of SCI. In cultured neurons, all LPE species promoted neurite outgrowth. Although several species demonstrated a tendency toward neuroprotection, only 16:0 LPE exhibited a statistically significant protective effect against glutamate-induced excitotoxic cell death. Intrathecal administration of 16:0 LPE after SCI reduced TUNEL-positive cells in the acute phase and attenuated lesion expansion at 8 weeks post-injury. Moreover, 5-HT fluorescence intensity was increased in 16:0 LPE-treated mice, suggesting enhanced serotonergic innervation. Furthermore, administration of 16:0 LPE after SCI significantly improved hind-limb motor performance compared with vehicle controls, as assessed by the Basso Mouse Scale. Collectively, these findings suggest that intrathecal administration of 16:0 LPE reduces secondary injury and promotes functional recovery following SCI. Our findings highlight its potential as a therapeutic candidate for SCI.

Spinal cord injury (SCI) can cause long-lasting locomotor deficits, pain, and mood disorders. Anatomical and functional outcomes are exacerbated by inflammation after SCI, which causes secondary damage. One promising target after SCI is manipulating the circadian system, which optimizes biology and behavior for time of day - including neuroimmune responses and mood- related behaviors. Circadian disruption after SCI is likely worsened by a disruptive hospital environment, which typically includes dim light-at-night (dLAN). Here, we hypothesized that mice subjected to SCI, then placed in dLAN, would exhibit worsened locomotor deficits, pain- like behavior, and anxiety-depressive-like symptoms compared to mice maintained in light days with dark nights (LD). C57BL/6J mice received sham surgery or moderate T9 contusion SCI, then were placed permanently in LD or dLAN. dLAN after SCI did not worsen locomotor deficits; rather, SCI-dLAN mice showed slight improvement in open-field locomotion at the final timepoint. Although dLAN did not alter SCI-induced heat hyperalgesia, SCI-dLAN mice exhibited an increase in mechanical allodynia at 13 days post-SCI compared to SCI-LD mice. SCI-LD and SCI-dLAN mice had similar outcomes using sucrose preference (depressive-like) and open-field (anxiety-like) tests. At 21 dpo, SCI-dLAN mice had reduced preference for a novel juvenile compared to SCI-LD, implying that dLAN combined with SCI may worsen this mood-related behavior. Finally, lesion size was similar between SCI-LD and SCI-dLAN mice. Therefore, newly placing C57BL/6J mice in dLAN after SCI had modest effects on locomotor, pain-like, and mood-related behaviors. Future studies should consider whether clinically-relevant circadian disruptors, alone or in combination, could be ameliorated to enhance outcomes after SCI.

Stroke is a leading cause of disability, causing chronic motor impairments in many survivors. Although recovery is correlated with cortical reorganization, the impact of lesion location on post-stroke reorganization is uncertain. We compared movement-related neural activity following experimental infarcts to the motor cortex (M1) or internal capsule in rats. Neural activity was recorded from motor and somatosensory regions during a skilled pellet retrieval task longitudinally during the course of recovery. Cortical lesions resulted in early behavioral recovery accompanied by widespread reductions in neural activity across ipsilesional regions, indicative of large-scale reorganization. In contrast, internal capsule lesions produced delayed recovery with no evidence of long-term ipsilesional cortical reorganization. These findings challenge the relevance of cortical reorganization for recovery from subcortical lesions and indicate that post-stroke recovery mechanisms are lesion-specific and that models targeting subcortical white matter are essential for maximizing translational relevance.

Spinal cord injury (SCI) disrupts brain-spinal cord communications and results in profound brain reorganization. Here, we apply high-resolution, voxel-based, whole-brain metabolic mapping using the [14C]-2-deoxyglucose autoradiographic method in mice to assess functional brain reorganization in a subacute stage (1 week after SCI). Right moderate contusive injury at the cervical 5 level (C5) was confirmed by glial fibrillary acidic protein (GFAP) immunohistochemical staining. SCI compared to sham-lesioned animals showed significant motor deficits (grip strength, rotarod) alongside decreases in glucose uptake in sensorimotor regions of the cortex, basal ganglia, and thalamus, which receive monosynaptic afferents (the ventral posterolateral thalamic nucleus, VPL) or multi-synaptic afferents from the spinal cord (the primary somatosensory and motor cortices, caudate putamen). In contrast, regions in the limbic system (the amygdala, accumbens nucleus, lateral septum, and hippocampus) and in the cerebellum demonstrated increases in glucose uptake in SCI animals. Most of these effects were noted bilaterally, suggesting functional reorganization involving higher order neural circuits bilaterally. The current findings underscore the broadness of brain reorganization in the subacute stage following incomplete SCI. Functional whole-brain metabolic mapping provides a roadmap for future targeted studies examining neuroplastic mechanisms in search of new therapeutic strategies.

Parkinsons disease (PD) is a neurodegenerative disorder in which gait disturbances are central to disability, yet their early manifestations remain poorly understood due to the difficulty of identifying prodromal PD in humans. Rodent models may help narrow this gap by approximating partial dopaminergic loss and enabling investigation of motor changes that precede overt symptoms. Here, we examined gait dynamics in Wistar rats following unilateral, low-dose 6-hydroxydopamine (6-OHDA) lesions in the substantia nigra pars compacta (SNc). Animals were assessed weekly for six weeks in the horizontal ladder test, where running velocity and footfall accuracy were quantified with markerless pose estimation using DeepLabCut (DLC). Lesioned animals exhibited greater tyrosine hydroxylase (TH)-reactivity asymmetry than controls, reflected behaviorally as persistent but gradually attenuating deficits in gait precision. Errors peaked at week three and remained above baseline through week six. Velocity was preserved across groups, but sex differences emerged. Control females accelerated more steeply over time, whereas lesioned females showed attenuated gains and greater variability, while males displayed more homogeneous velocity profiles across conditions. Together, these findings indicate that partial SNc lesions reveal sex-specific trajectories of motor adaptation, a feature relevant to modeling prodromal PD. Combined with DLC-based tracking, this framework offers a practical approach for detecting early behavioral markers and supporting the identification of preclinical motor features of PD.

Maturation of central nervous system neurons leads to loss of their intrinsic regeneration potential. In particular after injury of the adult spinal cord there is minimal regeneration of corticospinal axons, which control gait and fine movement. Previous work has shown that knockdown of PTEN to increase PIP3 levels can promote regeneration in young animals, but the effect is much less in adults probably due to low PIP3 production. Here, we have transduced sensorimotor cortex neurons with a hyperactive form of PI3K, PI3K{delta}, which increases PIP3 in mature neurons. This enables cortical neurons to regenerate corticospinal axons and improve behavioural outcomes. We used a C4 dorsal column lesion model in adult rats and injected the right motor cortex at 4 sites concurrently with a mixture AAV1-PIK3CD and AAV1-eGFP or titre matched AAV1-eGFP only. We allowed rats to survive for 6, 9, 12 or 16 weeks. Immunostaining showed 70 - 80% co-expression in cortical neurons which remained stable at both 12 and 16 weeks. We counted GFP labelled axons in 20 m spinal cord sections. In PI3KCD-treated animals many axons were seen to have regenerated around the margins of lesions, collecting into a knot of axons with the typical appearance of regeneration at the caudal end. Tracing down the cord, and excluding axons and neurites that could have come from unlesioned ventral CST, we found axons extending up to 1 cm below lesions, numbers decreasing with distance from the lesion. After 16 weeks there were circa 200 axons at the caudal end of lesions with a regeneration index of 0.2, with half this number at 12 weeks. Behavioural testing for 16 weeks revealed functional improvements in skilled paw reaching, grip strength and ladder rung walking in rats treated with PIK3CD compared to GFP only controls. In addition to behavioural testing, functional recovery of PIK3CD treated rats was confirmed with electrophysiological recordings during which we stimulated the right pyramid. Cord dorsum potentials (CDPs) above and below lesion and EMG forepaw distal flexor muscles showed greatly increased connectivity compared with GFP only controls, lesion only controls and uninjured shams. We conclude that forcing upregulation of PI3K{delta} in cortical neurons leads to robust regeneration after spinal cord injury that results in functional restoration.

Traumatic brain injury (TBI) induces a series of neuropathological changes in the brain including neurogenesis, an important cellular response involved in brain repair and regeneration. TBI-enhanced neurogenesis in the dentate gyrus (DG) of the hippocampus is of particular importance due its contribution to learning and memory functions. In the neurogenic process, proliferation and differentiation of neural stem cells (NSCs) follow a well-characterized sequence controlled by many factors including Notch1, which plays essential roles in regulating NSC fate determination under physiological conditions in both developing and adult brains. Following TBI, the dynamic changes of NSCs and the involvement of Notch1 on their development at different stages post-injury are not fully characterized. In the current study, we examined the impact of TBI and Notch1 on NSCs proliferation, survival and neuronal differentiation. Utilizing transgenic mice with tamoxifen-induced GFP expression and Notch1 knock-out in nestin+ NSCs, we examined DG neurogenic response at acute, subacute and chronic stages following a moderate lateral fluid percussion injury. We found that TBI enhanced a proliferative response in the DG at the acute stage following injury; however, this injury response was abolished when Notch1 was conditionally deleted from nestin+ NSCs. We also found that injury and Notch1 deletion drove NSCs committing fate choice towards neuronal differentiation. The results of this study provides further knowledge regarding TBI-induced neurogenic response and Notch1 as the key regulating mechanism.