Biology subjects

Ross, J. D.

Publications and source records attributed to Ross, J. D..

4 recordsLinked to original sources

bioRxiv2026

Chemogenetic excitation and play promote functional recovery in juvenile spinal cord injury

Functional recovery after spinal cord injury depends on whether reorganizing descending circuits form adaptive, task-specific relays rather than maladaptive ones. The corticospinal tract undergoes competitive, activity-dependent refinement during a defined juvenile window, so the timing and polarity of cortical activity may dictate whether injured circuits rewire usefully. Whether biasing cortical activity during this window can steer reorganization toward recovery, and whether naturalistic rehabilitation supplies the activity such steering requires, remain unknown. In juvenile rats we delivered excitatory or inhibitory chemogenetic receptors, or a control vector, to the forelimb motor cortex at postnatal day 5, induced a right cervical hemisection at postnatal day 14, and gave oral clozapine-N-oxide during nightly rough-and-tumble play from postnatal day 20 to 50. Play, the rehabilitation common to all groups, did not differ between them, isolating cortical-activity polarity as the manipulated variable. Outcomes spanned forelimb dexterity, reaching kinematics, cortical output by intracortical microstimulation, descending architecture by intersectional viral tracing, and frequency-dependent depression of the Hoffmann reflex. In untreated injured animals, cortical output re-lateralized maladaptively toward the intact forelimb, driving the ipsilateral (intact) limb in 11 of 15 evoked responses and 3 of 5 animals. Excitation preserved selective drive to the impaired forelimb (38 of 39 responses; concordant-site proportion Kruskal-Wallis H = 9.08, exact P = 0.0031), and pure ipsilateral re-lateralization was absent from all nine treated animals (3 of 5 control versus 0 of 9 treated; Fisher's exact P = 0.027). Across behavioural, kinematic, and anatomical measures a consistent excitatory > control > inhibitory gradient emerged. Excitation enhanced wrist elevation and forward extension during reaching, restored frequency-dependent depression of the Hoffmann reflex, and selectively recruited three parallel lesion-bypassing relays: interhemispheric cortico-cortical-spinal, cortico-reticulo-spinal, and cortico-propriospinal (ipsilesional cortical relay neurons F(2,14) = 56.96, P < 0.0001). Inhibition yielded the weakest behavioural recovery and least relay recruitment, and did not restore contralesional cortical drive. Cortical-activity polarity during a juvenile window thus acts as a developmental switch governing whether descending reorganization is adaptive or maladaptive. Guided excitation, paired with behaviourally meaningful activity, reshapes diffuse sprouting into structured, lesion-bypassing relays and corrects the spontaneous re-lateralization that otherwise misdirects recovery. These findings provide a translational rationale for activity-paired neuromodulation in paediatric spinal cord injury.

neuroscience↗

bioRxiv2026

Parabrachial-amygdala circuit cooperates with a posterior striatal area to drive opioid withdrawal aversion

Opioid addiction treatment is often hampered by the severe dysphoria of opioid withdrawal, but withdrawal treatments are limited by incomplete understanding of brain mechanisms involved. One area frequently implicated in withdrawal symptoms is the central amygdala, whose capsular portion (CeC) is particularly strongly activated during withdrawal. Additionally, a ventral posterior striatal region that resides near CeC, the interstitial nucleus of the posterior limb of the anterior commissure (IPACc), is also activated as strikingly as CeC. However, it is still unknown how these regions are activated, nor whether their activation explains the high intensity of withdrawal dysphoria. Using RNAscope, we found that c-fos expression is induced in the parabrachial nucleus (PB), a key glutamatergic afferent of CeC, after precipitated morphine withdrawal. Chemogenetic inhibition of PB glutamatergic neurons (VG2PB) nearly eliminated withdrawal-induced CeC c-Fos, without affecting IPACc c-Fos, indicating these two nuclei are activated by distinct sources. Furthermore, VG2PB inhibition markedly reduced somatic (jumping) and modestly reduced affective (place avoidance) withdrawal behavior. On the other hand, inhibition of CeC-projecting PB neuronal subtypes expressing calcitonin gene-related peptide (CGRP) or mu opioid receptor (MOR) reduced place avoidance without affecting jumping, indicating their specific role in withdrawal aversion. Strikingly, simultaneous inhibition of VG2PB and posterior striatal region containing IPACc robustly reduced withdrawal-induced place avoidance much more than the modest effects of either inhibition alone, suggesting their cooperative action in driving aversion. Our data suggests that PB-CeC circuit and posterior striatal area constitute a cooperative system driving opioid withdrawal aversion.

neuroscience↗

bioRxiv2026

Kinematics-based assessment of reaching and grasping movements in LRN ablated animals identifies a role for the LRN in endpoint stabilization and reach timing.

The lateral reticular nucleus (LRN) is thought to contribute to skilled forelimb control but its specific contributions to reaching and grasping remain unclear. In this paper, we examine skilled reaching in intact adult female Long-Evans rats after bilateral LRN ablation through single-pellet reaching tasks. Tasks were analyzed using sensitive quantitative kinematic analyses and qualitative behavioral scoring. Overall, limb transport was largely preserved after ablation, with results appearing in temporally restricted differences. The clearest deficits emerged in pellet-directed endpoint control. LRN-ablated animals showed broad variability in end-point covariance, endpoint spread, and increased trial-to-trial variability, indicating that the movement became less precise and less consistent. These effects were more consistent than any single spatial difference seen, suggesting that ablation of the LRN impairs movement refinement rather than inducing a simple directional bias, although the paw height during the reach was significantly effected. Reach duration also changed, but this temporal difference emerged later and was less prominent. Our results suggest that the LRN acts as an important contributor to endpoint stabilization and reach timing during skilled forelimb behavior.

neuroscience↗

bioRxiv2022

Composition and functionality of bacterioplankton communities in marine coastal zones adjacent to finfish aquaculture

Finfish aquaculture is one of the fastest-growing primary industries globally and is increasingly common in coastal ecosystems. Bacterioplankton is ubiquitous in marine environment and respond rapidly to environmental changes. However, little is known about the effect of the aquaculture in the bacterioplankton community. This study aims to examine aquaculture effects in the composition and functional profiles of the bacterioplankton community using amplicon sequencing along a distance gradient from two finfish leases in a marine embayment. Our results revealed natural stratification in bacterioplankton strongly associated to NOx, conductivity, salinity, temperature and PO4. Among the differentially abundant bacteria in leases, we found members associated with nutrient enrichment and aquaculture activities. Abundant predicted functions near leases were assigned to organic matter degradation, fermentation, and antibiotic resistance. This study provides a first effort to describe changes in the bacterioplankton community composition and function due to finfish aquaculture in a semi-enclosed and highly stratified embayment.

microbiology↗