Experimental Neurology

Spinal cord injury (SCI) disrupts long-distance communication between the brain and spinal circuits, resulting in persistent motor, sensory and autonomic dysfunction1. These deficits arise from the limited regenerative capacity of adult central nervous system (CNS) neurons and the presence of a growth-inhibitory extracellular environment. Among pathways that control voluntary movement, failure of corticospinal tract (CST) regeneration is a major contributor to impaired motor function. Strategies to promote regeneration have focused on enhancing the intrinsic growth capacity of injured neurons, such as through activation of the mTOR pathway via phosphatase and tensin homolog (PTEN) suppression, as well as reducing extrinsic inhibition through enzymatic digestion of chondroitin sulfate proteoglycans (CSPGs) using chondroitinase ABC (chABC). Because these mechanisms act through distinct but complementary processes, we investigated their combination as a strategy to improve regeneration. Adeno-associated viral (AAV) vectors are widely used to enhance intrinsic growth pathways and represent a clinically relevant platform for gene delivery. In contrast, CSPG digestion has primarily been achieved using lentiviral or focal delivery approaches. We therefore examined whether reducing extrinsic inhibition could be implemented using AAV2-mediated chABC delivery, alone and in combination with AAV2-retro-mediated PTEN knockdown, following cervical SCI. AAV2-mediated delivery of chABC produced robust and persistent CSPG digestion that extended beyond the injection site, and this spatial extent was influenced by viral dose and expression magnitude. Despite effective CSPG degradation, AAV2-chABC treatment did not improve functional outcomes relative to controls and did not enhance the effects of intrinsic growth activation via PTEN knockdown. Instead, AAV2-chABC treatment, alone or in combination with AAV2-retro-mediated PTEN knockdown, was associated with impaired motor performance in behavioral assays. These findings indicate that the extent and persistence of CSPG degradation critically shape functional outcomes after SCI and that simultaneous enhancement of intrinsic growth capacity and extracellular permissiveness does not necessarily translate into improved functional recovery. Together, these results underscore the importance of carefully controlling transgene expression levels and duration in AAV-based gene therapies, where suboptimal delivery parameters may offset the benefits of otherwise promising targets.

Traumatic brain injury (TBI) triggers complex and evolving secondary cascades that disrupt mitochondrial homeostasis and contribute to progressive neurodegeneration. Although mitochondrial impairment is a well-recognized driver of post-traumatic pathology, the spatial and temporal progression of mitochondrial dysfunction, particularly in regions distal to the injury site, remains poorly defined, and potential sex-specific responses remain understudied. Here, we performed a comprehensive mitochondrial-focused analysis in a mouse model of controlled cortical impact (CCI), quantifying mtDNA copy number (mtDNA-CN), mitochondrial gene expression, and protein markers regulating biogenesis, transcription, electron transport chain integrity, and mitophagy. Mitochondrial profiles were assessed across four brain regions (cortex at 2, 4, and 6 mm from the injury epicenter, and hippocampus) at four time points (6h, 12h, 24h, and 48h) in both female and male C57BL/6J mice. While mtDNA content exhibited only modest and region-restricted reduction, particularly near the injury core, transcriptional and protein-level changes were far more pronounced and sex-divergent. Females displayed extensive early cortical gene activation followed by widespread hippocampal suppression at 48 h across mitochondrial dynamics, OXPHOS, transcriptional regulation, and biogenesis pathways, accompanied by 48h in PGC-1, TFAM, and NDUFS1. In contrast, males showed minimal transcriptional disruption but demonstrated delayed compensatory increases in TFAM, NDUFS1, and p62 protein levels, suggesting activation of mitochondrial maintenance and recovery programs. These spatially and temporally distinct responses reveal fundamental sex-specific vulnerabilities in mitochondrial regulation after TBI. Together, our findings provide a direction to an integrated mitochondrial landscape of early post-injury events and identifies critical windows and pathways that may support sex-specific therapeutic targeting to restore mitochondrial function after TBI.

Parkinsons disease is characterized by progressive dopaminergic degeneration, yet motor symptoms emerge only after substantial neuronal loss - a dissociation that challenges the sensitivity of conventional behavioral endpoints in preclinical models. Here, we present a proof-of-principle study establishing a graded hemiparkinsonism model in adult male capuchin monkeys (Sapajus apella) through unilateral, MRI-guided stereotaxic injection of 6-hydroxydopamine into the substantia nigra pars compacta. Three toxin concentrations (4, 10, and 40 mg/mL; n = 3) were tested alongside a vehicle-injected sham control (n = 1). Motor function was assessed longitudinally before and after surgery using a three-task battery comprising the Staircase test, Tube test, and Brinkman board, capturing complementary dimensions of motor functions, including gross lateralization, forelimb use asymmetry, and fine digit coordination. Critically, we introduce a novel sequence-deviation metric applied to Brinkman board performance data to quantify disruption in the spatial organization of pellet retrieval independently of task success. Post-surgical tyrosine hydroxylase immunohistochemistry combined with optical fractionator stereology revealed ipsilateral dopaminergic cell losses of 47%, 59%, and 44% relative to the contralateral hemisphere across the three treated animals, with the sham showing no meaningful hemispheric difference. Behavioral impairments were heterogeneous and strategy-dependent: task completion rates were largely preserved, whereas fine motor strategy analysis revealed post-lesion increases in retrieval sequence disorganization in two of three animals. Exploratory regression analyses suggested that strategy-level metrics were more sensitive to nigrostriatal degeneration than global performance measures. These findings demonstrate that capuchin monkeys subjected to unilateral 6-hydroxydopamine lesions reproduce clinically relevant features of hemiparkinsonism and that motor sequence analysis constitutes a sensitive readout of subclinical dopaminergic dysfunction, and can outperform conventional performance-based metrics detecting early motor alterations, therefore a potential biomarker of subclinical dopaminergic dysfunction, with implications for early detection paradigms in Parkinsons disease research.

Parkinsons disease (PD) is characterised by progressive dopaminergic neurodegeneration in the substantia nigra, leading to debilitating motor dysfunction. Current treatments remain largely symptomatic, highlighting the need for disease-modifying therapies. {beta}1 integrin, implicated in neuroinflammation and trophic signalling, represents a candidate therapeutic target. We investigated whether allosteric {beta}1 integrin modulation could attenuate motor asymmetry in the unilateral 6-hydroxydopamine (6-OHDA) mouse model of PD. Adult male C57BL/6 mice received intracerebral 6-OHDA into the substantia nigra. The anti-{beta}1 integrin antibody JB1a (50 {micro}g) was administered prophylactically (3 days pre-lesion) or therapeutically (3 or 7 days post-lesion). Motor asymmetry was assessed through spontaneous circling (5 min) and apomorphine-induced (0.5 mg/kg s.c.) circling (30 min). 6-OHDA induced dose-dependent contralateral circling, confirming nigrostriatal lesion. Pre-treatment with JB1a (3 days before 6-OHDA) reduced apomorphine-induced circling, although this did not reach statistical significance (28.5 {+/-} 12.8, n = 4 versus 38.6 {+/-} 7.5, n = 8; p>0.05). Post-treatment at 3 days post-lesion produced no statistically significant change in either spontaneous or apomorphine-induced circling (p>0.05). Post-treatment at 7 days post-lesion reduced apomorphine-induced circling by approximately 50%, with values returning to those of sham-operated controls (n =8-9; p<0.01). These findings, obtained in a murine 6-OHDA model, indicate that allosteric {beta}1 integrin modulation attenuates lesion-induced motor asymmetry with apparent temporal specificity. As apomorphine-induced rotation reflects post-synaptic dopamine receptor supersensitivity rather than direct neuronal preservation, and as histological confirmation of dopaminergic integrity was not obtainable in this study, the present data should be interpreted as proof-of-concept behavioural evidence requiring further mechanistic and translational validation in models incorporating -synuclein pathology. The findings are not directly generalizable to human Parkinsons disease. The histological confirmation of lesion extent was not available and as such the behavioural findings are correspondingly interpreted as a proof-of-concept observation requiring histological replication.

Tau protein has been implicated as an important mediator of traumatic brain injury (TBI). Adult human brain expresses 6 tau isoforms expressing 3 (3R) or 4 (4R) microtubule binding sites; adult mouse brain expresses only 4R tau. A role for tau isoform expression on TBI disease course is tested using wild-type C57/BL6 mice (WT) and C57/BL6 with a knocked-in human tau coding region (MAPTKI). Uninjured WT and MAPTKI mice have similar brain histology and behavior as they age. At subacute times (14 days post-injury (DPI)), injured MAPTKI mice have less white matter damage with similar neuronal loss as WT. At chronic times (90DPI), MAPTKI mice demyelinate while WT mice remyelinate. At 14DPI, tau phosphorylation differs between WT and MAPTKI mice. At 90DPI, thioflavin-S+ protein aggregates in MAPTKI corpus callosum are higher than WT. At 14 or 90DPI, WT and MAPTKI mice acquire Barnes maze, WT retention is impaired at 14DPI and MAPTKI retention impaired at 90DPI. At 14DPI, only MAPTKI mice acquire and retain active place avoidance; at 90DPI, only WT mice acquire active place avoidance. At 14DPI, only injured MAPTKI mice acquire alternating T-maze. These data suggest that WT and MAPTKI differ in both subacute and chronic disease course. At 14DPI, WT mice have greater white matter damage and behavioral impairments than MAPTKI mice. At 90DPI, impairments in WT mice partially recover, yet worsen in MAPTKI mice. This data suggests that 3R tau isoform expression alters the disease course of head injury. HighlightsPost-injury disease course of MAPTKI mice expressing 3R and 4R tau differs from wild-type mice expressing only 4R tau. At subacute times post-injury, MAPTKI mice have less white matter, yet similar gray matter, injury than wild-type mice. At chronic times post-injury, white matter damage in MAPTKI worsens. At subacute times post-injury, MAPTKI mice have fewer behavioral deficits than wild type mice. At chronic times post-injury, MAPTKI mice develop behavioral deficits not present at subacute times.

Falls are a common and debilitating feature of Parkinsons Disease (PD) patients. Prefrontal acetylcholine (ACh) deficits, as well as nigrostriatal dopamine deficits, are implicated in vulnerability to falls. PD patients with loss of cortical ACh and associated cognitive dysfunction experience a higher rate of falls than PD patients without cortical ACh loss. In addition, chemogenetic inhibition of basal forebrain (BF) projections in rats increases the vulnerability to falls on a balance beam task. Here, the impact of transient optogenetic inhibitions of BF-cortical cholinergic projections was assessed in rats with dorsomedial striatal dopamine lesions during traversal of straight or zig-zag balance beams in the Michigan Complex Movement Control Task (MCMCT). Adding transient optogenetic inhibition of BF-cortical cholinergic projections in rats with striatal dopamine lesions increased falls above the level produced by striatal dopamine lesions or BF ACh inhibition alone, especially on the challenging zig-zag task. These results support the critical role of BF-cortical cholinergic circuits in alleviating vulnerability to falls in PD patients with striatal dopamine loss, suggesting that it is combined loss of BF cholinergic projections and striatal dopamine that leads to greatest vulnerability to falls and related complex movement impairments.

Individuals with chronic cervical spinal cord injury (SCI) retain voluntary motor unit (MU) activation below the level of the lesion despite profound impairments in muscle relaxation, yet the MU-level mechanisms underlying this dissociation remain unclear. Here, we investigated MU recruitment and derecruitment dynamics using high-density surface EMG (HD-sEMG) and intramuscular EMG (iEMG), in functionally paralyzed muscles across open- and closed-loop tasks in four participants with chronic cervical SCI. Building on prior work that distinguished task-modulated from non-modulated MUs, we combined closed-loop MU feedback with targeted intramuscular implants to determine whether tonic units remain accessible to voluntary control and whether distinct firing phenotypes coexist within individual motor pools. Participants voluntarily recruited MUs and modulated discharge rates (45.2%), but a significant fraction (54.8%) of active MUs could not be derecruited during attempted relaxation. Quantitative analysis of 409 MUs revealed that derecruitment impairment spans a graded continuum rather than the binary distinction between modulated and non-modulated units reported previously. Three phenotypes, controllable (45.2%), modulated-tonic (42.8%), and tonic (12%), partition this spectrum based on derecruitment timing, discharge regularity, and firing persistence and coexist within the same motor pools, including within single muscle compartments sampled intramuscularly. Kaplan-Meier survival analysis confirmed graded derecruitment dynamics: controllable units ceased firing within 500 ms of rest onset, whereas most tonic units persisted throughout the observation window (log-rank{chi} 2= 164.10, P < 0.001). Tonic units displayed highly regular discharge consistent with intrinsic motoneuron excitation via persistent inward currents (PIC). Phenotypes were consistent across recording modalities and task contexts, and phenotype effects on derecruitment metrics exceeded movement-type effects by an order of magnitude. These findings identify impaired MU derecruitment as a core feature of spastic paralysis, driven by maladaptive motoneuron and spinal network properties that preserved descending drive cannot fully counteract. A proof-of-concept spike-train-level temporal filter selectively suppressed tonic firing while preserving voluntary modulation (>94% correlation retained), demonstrating a physiologically grounded strategy for improving neural interfacing after SCI.

Older adults are among the fastest growing groups of traumatic brain injury (TBI) patients and sustain disproportionately poor chronic outcomes. Despite this, the preclinical aging-TBI literature is limited. Beyond the limited presence of aging TBI studies, most studies published in this domain use moderate-to-severe, open head models of TBI, rather than closed head models of mild TBI (mTBI) and repetitive mTBI (rmTBI), the most clinically prevalent presentation. Whether age modulates the chronic behavioral consequences of rmTBI is unknown. In the current study, young (3-4 months) and aged (18-19 months) male C57BL/6 mice received either five mTBIs on alternating days to model rmTBI or sham procedures and underwent behavioral testing in the chronic phase for spatial memory and anxiety-related behavior. Because cross-age behavioral comparisons are confounded by age-related declines in activity and by large sample sizes necessary to detection interaction effects, we applied a three-tier analytical framework combining within-age comparisons, sham-normalized inter-age comparisons, and factorial two-way ANOVA. Contrary to our hypothesis that aging would worsen rmTBI behavioral deficits, age produced domain-divergent effects. Spatial memory deficits were directionally consistent in both young and aged mice but was attenuated in the aged group. Conversely, anxiety-related behavior emerged selectively in the aged mice showing increased thigmotaxis. Locomotion was driven by age alone, with no injury effect, confirming that the aged anxiety signal was not a locomotor artifact. A post-hoc sensitivity analysis indicated that resolving the Age x Injury interaction effect would require at least 44 animals per group. These findings show that age shapes the affective, but not the cognitive, consequences of chronic rmTBI, and underscoring that statistical strategy is inseparable from design in factorial injury studies.

Neonatal hypoxia-ischemia (HI) injury is a major risk factor for lifelong cognitive impairments. Given its systemic impact, the neural mechanisms of impairments associated with HI injury remain unclear. In this study, we used a mouse model of neonatal HI injury to study its impact on goal-directed behavior and neural activity in adulthood using a head-fixed visual discrimination task. While neonatal HI injury did not impair discriminability or learning, it was associated with increased motor output in form of licking, faster reaction times and liberal decision bias, indicating an impulsive-like phenotype. These behavioral changes were accompanied by suppressed neuronal activity in the primary visual cortex (V1) and elevated cue-driven fluctuations in trial-to-trial firing variability in the prefrontal cortex (PFC), the latter of which was predictive of decision bias in HI mice. Our findings identify the long term impact of neonatal HI injury on goal-directed behavior, describe in detail the task-related patterns of neural activity in HI mice, and implicate abnormal neural variability in the PFC as a driver of impulsive-like behavior in adults that suffered neonatal HI injury.

Traumatic brain injury (TBI) is a condition of high incidence worldwide, but remains mostly undertreated. Previous observations in preclinical studies pointed to a beneficial effect of insulin-like growth factor 1 (IGF-1) in TBI. As brain injury is associated to loss of IGF-1 sensitivity, we tested the therapeutic potential of AIK3a305 (AIK3), a novel IGF-1 sensitizer. Twenty-four hours after mild TBI induced by controlled impact, mice received daily intraperitoneal injections of AIK3 during 4 weeks. We found that TBI-associated sensorimotor disturbances measured with the adhesive-removal test were reverted by AIK3 treatment. In addition, neurological and cognitive disturbances measured by the neurological severity score and Y maze respectively, were also ameliorated by treatment with the IGF-1 sensitizer, whereas increased anxiety after mild TBI was also normalized by AIK3. Circulating levels of IGF-1 were increased after AIK3 treatment in TBI mice, while serum IL-6 levels, a biomarker of inflammation associated to TBI were similar to control mice treated with AIK3. Transcriptomic analysis determined that treatment with AIK3 widely affected gene expression in TBI brains, showing a general reduction in both up- and down-regulated genes. Collectively, these data support the use of IGF-1 sensitizers such as AIK3 for treatment of TBI.

Brain neuromodulatory systems exert powerful effects on local neuronal circuit function and behavior. In addition to classical actions directly on neurons, growing evidence indicates that neuromodulators also recruit Ca2+-dependent astrocyte mechanisms to regulate synaptic plasticity and network function. The dorsal striatum integrates cortical and thalamic inputs under strong dopamine (DA) and acetylcholine (ACh) neuromodulatory control. To what extent the circuit and behavioral effects of striatal ACh and DA depend on astrocyte Ca2+ activity remains unclear. We show that locomotion elicits robust DA, ACh, and astrocyte Ca2+ activity in the dorsolateral striatum (DLS). DA and ACh release exhibits a negative correlation on a fast time scale but shows a positive correlation during continuous locomotion as slower astrocyte Ca2+ activity builds. Higher ACh and DA release is associated with higher astrocyte events, suggesting that both neurotransmitters drive astrocyte activity. In agreement, pharmacological blockade of muscarinic ACh or D1/D2 DA receptors decreases locomotion-evoked astrocyte Ca2+. Closed-loop optogenetic inhibition of striatal cholinergic interneurons (CINs) during locomotion reduces astrocyte Ca2+ activity, demonstrating a causal contribution of ACh release to astrocyte activity. Locomotion related ACh release was severely compromised in a mouse model of Parkinsons disease (PD), with the dual loss of DA and ACh attenuating astrocyte Ca2+ activity. Facilitating astrocyte cholinergic signaling via chemogenetics improved both calcium activity and motor deficits in our recent work. Thus, the pathophysiology of PD in part involves attenuated astrocyte Ca2+ signaling, placing these non-neuronal cells as a prime underexplored therapeutic target for PD.

Temporal lobe epilepsy (TLE) is a heterogeneous disorder with most clinical presentations involving unilateral or bilateral hippocampal seizure onsets. Antiseizure medications are often ineffective for TLE, and epilepsy surgery can have variable outcomes. Risk factors for TLE are readily identifiable and typically precede chronic epilepsy, providing a window of opportunity for preventative treatments. However, there are currently no clinically approved anti-epileptogenic therapies. In this study, we investigate the role of Wnt signaling in epileptogenesis using two mouse TLE models, the intrahippocampal kainate model of unilateral TLE (IHK), and the intraperitoneal kainate model of bilateral TLE (IPK). We specifically examined adult-born immature dentate granule cells as these cells have been heavily implicated in the pathogenesis of TLE and clinical TLE is typically initiated in adulthood. We observed that adult-born immature dentate granule cells undergo pathological morphological changes during epileptogenesis in both the IHK and IPK models of TLE. When compared across epileptogenic zones, however, these changes differed between the two models. Wnt signaling also decreased in these cells in epileptic mice during the epileptogenic period. When mice were treated with SB415286, a highly selective Wnt activator, Wnt signaling in immature dentate granule cells was restored to baseline levels and pathological remodeling changes were reduced in both models. These data therefore suggest that a reduction in Wnt signaling in immature dentate granule cells plays an etiological role in epileptogenesis, and that restoring Wnt signaling using Wnt activating drugs or alternative agents may have therapeutic potential as an anti-epileptogenic strategy in TLE.

L-DOPA remains the most effective therapy for Parkinsons disease (PD), yet its chronic use often induces involuntary movements known as L-DOPA-induced dyskinesia (LID). While abnormal cholinergic interneuron (ChI) activity is a hallmark of both PD and LID, emerging evidence suggests that the temporal organization of acetylcholine (ACh) signaling, rather than its overall magnitude, may determine its functional impact. Under physiological conditions, ChIs exhibit intrinsic delta-frequency activity reflected in coordinated, slow oscillations of extracellular ACh, which are thought to organize striatal network function and movement pattering. To determine how dopamine (DA) depletion and L-DOPA treatment reshape these ACh dynamics, we used in vivo GRAB-ACh fiber photometry in the unilateral 6-OHDA mouse model. DA depletion disrupted slow ACh rhythmicity, reducing delta-band regularity while increasing higher-frequency phasic activity. Acute L-DOPA broadly suppressed ACh activity across frequencies, partially normalizing this imbalance, but without restoring slow temporal structure. In addition, chronic L-DOPA treatment, associated with established dyskinesia, further impaired delta-band coordination in the DA-depleted striatum during the ON state, while OFF-state activity retained lesion-associated features. The anti-dyskinetic agent amantadine restored low-frequency temporal structure both before and after L-DOPA exposure. Together, these findings reveal a state-dependent reorganization of striatal ACh dynamics, characterized by a shift from coordinated slow oscillations to irregular phasic activity following DA loss, and a further breakdown of slow temporal organization during dyskinetic states. These results highlight the temporal structure of cholinergic signaling as a critical and underappreciated dimension of striatal function in PD and LID.

Cortical slow oscillations (SOs; 0.1-1.0 Hz) are suppressed after ischemic stroke, and their recovery is often read as evidence of circuit reorganization and functional restoration. Whether SO recovery is coupled to behavioral improvement, and whether pre-stroke network organization shapes recovery, has not been tested within individual animals. Using longitudinal wide-field calcium imaging in Thy1-GCaMP6f mice (n = 25), we tracked ipsilateral and contralateral SO power across baseline, 24 hours, and one week after photothrombotic stroke of the left somatosensory forepaw cortex, classifying animals by the presence (STI+; n = 14) or absence (STI-; n = 11) of secondary thalamic injury (STI). Acute ipsilateral SO power was markedly suppressed and tracked concurrent behavioral deficit ({rho} = -0.718, p < 0.001), capturing dysfunction beyond lesion volume (partial {rho} = -0.448, p = 0.025). By one week SO power had recovered, yet this recovery was dissociated from forelimb use. Week 1 SO power showed no association with behavior in any region or hemisphere (all |{rho}| [&le;] 0.074, all p > 0.5), and STI+ and STI- animals recovered SO equivalently despite STI+ animals remaining more impaired (p = 0.011). In contrast, pre-stroke SO laterality predicted week 1 forelimb use independent of infarct size ({rho} = -0.518, p = 0.008; partial {rho} = -0.446, p = 0.026). Acute SO suppression thus tracks injury severity beyond infarct volume, but its recovery does not track functional recovery; instead, pre-stroke interhemispheric SO balance predicts outcome, identifying pre-injury brain state as an underappreciated prognostic factor. Significance StatementSlow oscillations are suppressed by stroke and recover over time, and that recovery is often read as a sign of functional repair. Whether oscillatory recovery actually tracks behavioral recovery had not been tested within individual animals. Tracking slow oscillation power and forelimb use longitudinally, we show that acute suppression marks injury severity beyond lesion size, but that recovery of slow oscillation power over the first week does not track recovery of forelimb use: animals with good and poor outcomes recover oscillations equivalently. What predicts recovery is instead the interhemispheric balance of slow oscillation power (its relative distribution across the two hemispheres) present before the stroke. These results separate oscillatory recovery from functional recovery and point to pre-injury brain state as a prognostic factor.

Stroke is the leading cause of chronic disability in the United States, and advancing age is associated with worse recovery. Despite this, relatively little is known about how aging influences the repair and reorganization of neural circuits and large-scale cortical networks after stroke. To address this question, we compared cortical network dynamics and behavioral recovery after focal photothrombotic stroke in forepaw somatosensory cortex in young (3-month-old) and aged (18-month-old) Thy1-GCaMP6f mice. Both young and aged mice developed significant somatomotor deficits after stroke; however, only young mice exhibited substantial behavioral recovery despite similar infarct volumes across groups. Two age-dependent effects on cortical network function emerged. First, somatosensory-evoked activity and somatosensory functional connectivity were disrupted in both cohorts early after stroke, but their trajectories diverged over time. Forepaw-evoked GCaMP responses in the affected cortex were similarly reduced in both groups early after stroke; yet by 7 weeks, responses recovered in young mice but remained persistently depressed in aged animals. Likewise, bihemispheric somatosensory functional connectivity was initially disrupted in both groups but improved between 1 and 7 weeks only in young mice. Second, global temporal measures of network function evolved differently after stroke. At baseline, stimulus-locked fidelity and interhemispheric coherence were higher in young than aged mice, but after stroke, these measures declined in young animals to levels comparable to aged mice and did not recover by 7 weeks. Stroke also altered large-scale cortical entrainment dynamics, and reductions in cortical entrainment area between baseline and 1-week post-stroke predicted long-term behavioral recovery across animals. Together, these findings indicate that impaired behavioral recovery in aged mice reflects a failure of damaged somatosensory networks to reorganize, whereas recovery in young mice occurs despite persistent degradation of global network fidelity and coherence. These results highlight age-dependent mechanisms of circuit repair after stroke and suggest a potential network-level basis for chronic deficits in stroke survivors. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=65 SRC="FIGDIR/small/720447v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@1f23999org.highwire.dtl.DTLVardef@1a3a433org.highwire.dtl.DTLVardef@712dd5org.highwire.dtl.DTLVardef@780eaa_HPS_FORMAT_FIGEXP M_FIG C_FIG

Aldehyde dehydrogenase 1A1-positive (ALDH1A1+) dopaminergic neurons (DANs) are preferentially vulnerable in Parkinsons disease (PD), yet how their activity is modulated by presynaptic inputs remains poorly defined. Here we investigated the role of glutamatergic input by conditionally deleting Grin1, which encodes a critical NMDA receptor (NMDAR) subunit, in ALDH1A1+ DANs. Grin1 conditional knockout (cKO) mice displayed normal locomotion and motor learning; however, females exhibited enhanced operant reward acquisition and excessive feeding with transient weight gain following food restriction. To determine regional contributions, Grin1 was selectively knocked down in ALDH1A1+ DANs of either the ventral tegmental area (VTA) or substantia nigra pars compacta (SNc). VTA-specific knockdown in females was sufficient to reproduce the post-restriction feeding and weight gain phenotype. Bulk whole-brain mRNA sequencing revealed pronounced sex-dependent transcriptional changes, primarily in female Grin1 cKO mice after food restriction. Many differentially expressed genes were associated with mitochondrial function, energy metabolism, and synaptic signaling. Together, these findings reveal a sex-specific role for NMDAR-mediated glutamatergic input to ALDH1A1+ VTA DANs in regulating feeding behavior, providing mechanistic insight into how dysfunction of this vulnerable subpopulation may contribute to PD-associated compulsive eating disorders. Key FindingDisrupted NMDA receptor-mediated glutamatergic input to ALDH1A1+ DANs drives sex-specific feeding abnormalities relevant to PD-associated compulsive eating disorders.

Post-stroke inflammation contributes to poor outcomes in both clinical and experimental studies. Interleukin-6 (IL-6) is a key inflammatory mediator in ischemic stroke, and higher circulating IL-6 levels are associated with greater stroke severity and worse clinical outcomes. Targeting IL-6 signaling therefore represents a potential therapeutic strategy. We tested whether inhibition of IL-6 signaling with the IL-6 receptor (IL-6R) blocking antibody tocilizumab (TCZ) improves recovery after experimental stroke. Aged mice (18-20 months) underwent 60 minutes of middle cerebral artery occlusion. TCZ (20 mg/kg) was administered 5 hours after ischemia onset, and behavioral outcomes were assessed weekly for 5 weeks. Delayed TCZ treatment improved long-term functional recovery in aged male mice but not in aged females. To explore this difference, we measured circulating soluble IL-6R (sIL-6R) levels in mice and patients with ischemic stroke. Females exhibited significantly higher post-stroke sIL-6R levels. Increasing the TCZ dose to 100 mg/kg restored efficacy in aged female mice and improved long-term outcomes. These findings support a role for IL-6R pathway modulation in improving recovery after experimental stroke and suggest that therapeutic response may differ by sex and target availability, potentially related to differences in circulating sIL-6R after ischemic injury.

Traumatic brain injury (TBI) has long-term consequences that include chronic traumatic encephalopathy (CTE) and an elevated risk for Alzheimer Disease (AD). These dementias ultimately manifest as tauopathies but may begin with acute neuronal dysfunction including post-traumatic seizures. Provocative evidence suggests that these prodromal seizures are a viable target to mitigate the later onset of dementias, and anti-epileptic drugs (AED) that increase the threshold of action potentials have indeed been shown to mitigate later tauopathies[1, 2]. Here, we test whether AEDs and other compounds that modulate synaptic transmission, applied immediately after TBI, can also act as prophylactics that block subsequent CTE-like tau aggregation and neurodegeneration in a larval zebrafish model. Levetiracetam (LEV) is an AED that modulates synaptic vesicle release. Application of LEV immediately following TBI abrogated TBI-induced tau tau aggregation (IC50 = 3.168 x10-3 mM) and cell death in the larval zebrafish TBI model. We next considered a polypharmacy approach involving mGluR2, because mGluR2 positively allosteric modulators (PAMs) such as JNJ-42153605 have previously been able to improve LEVs action in reducing some recalcitrant forms of seizure in a mouse model. We found that JNJ-42153605 was itself effective at blocking TBI-induced tau aggregation (IC50 = 8.691 x10-5 mM). Moreover, a subeffective dose of JNJ-42153605 (10-5 mM) was able to substantially improve the efficacy of LEV (~16-fold) in its prophylactic actions. Thus, LEV and JNJ-42153605 applied briefly after TBI offer a potent polypharmacy approach, at least in our preclinical animal model, to tackle the later tau aggregation and neurodegeneration that follows from TBI neurotrauma. These results warrant further investigation, including testing into mammalian TBI models (with longer disease course).

ObjectiveThe ketogenic diet (KD) is a high-fat, low-carbohydrate intervention widely used to treat drug-resistant epilepsy, thought to reduce seizures through a combination of metabolic, neuronal, and microbiota-dependent mechanisms. Additionally, recent studies suggest that the anticonvulsant effects of KD require the gut microbiota, with taxa such as Akkermansia and Parabacteroides contributing to seizure protection by modulating host neurotransmitter balance and neural excitability. While KD has been shown to be effective in reducing seizure burden across different epilepsies, its antiseizure effect on infection-driven seizures, which are often driven by acute neuroinflammation, has not been evaluated. Here, we evaluated the effects of KD on seizure burden, neuroimmune responses, and gut microbiota composition in the Theilers murine encephalomyelitis virus (TMEV) model of virus-induced epilepsy. MethodsMice were maintained on either a KD or a normal diet prior to intracerebral TMEV infection. Seizures were induced by handling and scored twice daily from day 3 to 7 post-infection. Neuroimmune responses were assessed by flow cytometry, and fecal microbial composition was analyzed using 16S rRNA gene sequencing. ResultsDespite achieving ketosis, KD did not reduce seizure incidence, seizure burden, or seizure severity during acute TMEV infection. KD also did not significantly alter overall immune cell infiltration into the central nervous system, indicating limited effects on global neuroinflammation. However, KD significantly reshaped the gut microbiota, reducing alpha diversity (richness, Shannon diversity, and evenness) and strongly altering community structure with clear separation between diet groups, including enrichment of taxa such as Akkermansia, Acetatifactor, Dorea, and Flintibacter, and depletion of fiber-associated taxa including Bifidobacterium and Roseburia. However, these microbial shifts were insufficient to mitigate inflammation-driven seizures. SignificanceThese results demonstrate that KDs anticonvulsant efficacy is highly context-dependent, and that KD-driven changes in microbiota- and metabolite-mediated mechanisms may be ineffective against infection-associated epilepsy, suggesting that inflammation-driven seizures require distinct therapeutic approaches. Key pointsO_LIThe ketogenic diet (KD) does not reduce acute seizure incidence and severity during TMEV infection despite achieving ketosis C_LIO_LIKD does not induce neuroinflammatory changes associated with seizure outcomes C_LIO_LIKD strongly reshapes gut microbiota, reducing diversity and altering community structure. C_LIO_LIMicrobiota changes are insufficient to protect against inflammation-driven seizures C_LIO_LIKD anticonvulsant effects are context-dependent and ineffective in infection-driven epilepsy C_LI

Background and PurposeMild hypothermia provides potent neuroprotection in experimental ischemic stroke, however, its implementation in awake stroke patients is hampered by the induction of intense shivering and inconsistent body temperature control. Pharmacological activation of peripheral/peritoneal TRPV1 channels with non-pungent capsinoids offers a means to induce hypothermia while minimizing TRPV1 activation in the injury region. We tested whether capsinoid-mediated mild hypothermia, initiated within the post-stroke period, reduces brain injury and improves functional outcomes in aged mice. MethodsAged (18-20 months) male and female C57BL/6 mice underwent either permanent distal middle cerebral artery (MCA) occlusion (pdMCAO) or 60-minute MCA occlusion/reperfusion (MCAO/R). At 2 or 4 hours after stroke, mice received intraperitoneal injections of vehicle or capsinoids (>97% purity; 40 mg/kg) every 90 minutes to induce mild hypothermia for 4.5-6 hours. Core temperature was monitored by wireless probe. After pdMCAO, infarct volume was quantified at post-stroke day 3 (PSD3) by TTC and brain atrophy at PSD30 by iodine-enhanced microCT; sensorimotor function (DigiGait, forelimb grip strength, foot fault) was assessed at PSD7 and PSD30. Survival was the primary measured outcome for MCAO/R. ResultsCapsinoids induced a rapid and sustained reduction in core temperature of 2-4{degrees}C, independent of sex. In the pdMCAO model, capsinoid-induced hypothermia reduced infarct volume by 48% at PSD3 and decreased chronic cortical tissue loss by 44% at PSD30. Capsinoid-treated mice showed significant improvements in gait, grip strength, and contralateral foot fault performance at PSD7 and PSD30. In the MCAO/R model, survival was significantly higher in capsinoid-treated mice (80%) versus vehicle controls (33%) through PSD3. ConclusionsIntraperitoneal capsinoid administration after stroke induces mild hypothermia in aged mice and confers robust acute neuroprotection and improved chronic functional outcome and survival. These preclinical findings add support for the use of capsinoids as a means to target peripheral thermoeffectors for promoting neuroprotective hypothermia in conscious stroke subjects.