Biology subjects

Cornish, J.

Publications and source records attributed to Cornish, J..

7 recordsLinked to original sources

bioRxiv2026

Multi-faceted role of dopamine afferents to the ventral pallidum in reward processing

The ventral pallidum (VP) is necessary for reward processing and a key node in dopamine (DA) pathways. Yet the direct DA inputs have not been studied during reward learning. Here, we elucidate the role of VP DA in reward processing using circuit tracing, fibre photometry, and behavioural pharmacology in male rats. We show that VP receives both non-DA and DA inputs from the midbrain. During an instrumental reward conditioning paradigm, we characterized VP DA activity using a DA sensor (GRAB_DA1h) across learning, extinction, re-acquisition, and motivational test. Followed by pharmacological manipulation using the DA-antagonist (fluphenazine) in VP to demonstrate a causal role in reward learning and motivation. Together our findings advance the functional contributions of non-canonical mesolimbic DA pathways.

animal behavior and cognition↗

bioRxiv2026

Subthalamic Nucleus dynamically encodes reward value and cognitive flexibility

The subthalamic nucleus (STN) is classically associated with motor control but is increasingly recognised as a key component of the neural circuits underlying cognition. However, how the STN encodes learned reward associations and updates these representations when environmental contingencies change remains unclear. Here, we combined fibre photometry calcium imaging and chemogenetic inhibition to identify the contribution of the STN in reward learning and cognitive flexibility. During established Pavlovian conditioning, calcium imaging of the STN showed distinctive responses to reward predictive cue and reward delivery, while no response was detected to unrewarded cues. Upon reversal of reward predictive cues, STN activity initially remained associated with the previously rewarded cue before remapping to the newly rewarded cue as animals acquired the updated contingency. Chemogenetic inhibition of the STN impaired cue discrimination on established Pavlovian conditioning, delayed reversal learning, and disrupted outcome-specific Pavlovian-to-instrumental transfer. Together these results demonstrate that STN activity is required for flexible updating of learned reward associations and goal-directed behaviour. These findings establish the STN as a dynamic integrative hub that encodes and updates learned reward representations to support cognitive flexibility, extending its role beyond motor control to include goal-directed behaviour. We show STN activity tracks reward-predictive cues and updates when contingencies reverse. Overall, these findings demonstrate that the STN is not just downstream of cortical control but actively supports updating of reward associations.

neuroscience↗

bioRxiv2026

SpinForecast: chain-free probabilistic backbone assignment of intrinsically disordered proteins from NMR chemical shifts

Assigning peaks in NMR spectra to specific residues is an essential but time-consuming step in the study of intrinsically disordered proteins (IDPs). Conventional approaches rely on building chains of sequential connectivities between peaks, which are particularly prone to failure in disordered systems due to spectral overlap, missing peaks, and proline-rich sequences. Here we present SpinForecast, a tool that performs chain-free probabilistic backbone assignment of IDPs from chemical shifts alone, without requiring peaks to be linked into sequential chains. SpinForecast predicts residue-specific chemical shift distributions from a disorder-filtered subset of the Biomolecular Magnetic Resonance Data Bank (BMRB), incorporating nearest-neighbour residue effects and corrections for temperature and pH. Experimental chemical shifts are then assigned to residues by Bayes theorem, using residue-specific chemical shift distributions as likelihoods. We validate SpinForecast on three disordered proteins, IAPP (37 residues), NUPR1 (82 residues), and JPT2 (218 residues), achieving 100% confidence assignments for 74%, 57%, and 44% of in-distribution peaks, respectively, all with at least 99% accuracy. Where single assignments cannot be determined for these systems, the correct assignment was contained within the returned set of candidate assignments in greater than 97% of cases. SpinForecast is freely available at https://tools.bindresearch.org/bindbox/SpinForecast.

biophysics↗

bioRxiv2026

Liquid liquid phase separation of the intrinsically disordered protein JPT2compartmentalizes components of NAADP-evoked Ca2+ signaling

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a Ca2+-releasing second messenger that activates two-pore channels (TPCs) on endosomes and lysosomes. Rather than binding TPCs directly, NAADP acts through cytoplasmic NAADP-binding proteins (NAADP-BPs) which are essential for endolysosomal Ca2+ release. Here we characterized the properties of two recombinant, purified NAADP-BPs: Jupiter Microtubule Associated Homolog 2 (JPT2) and like-Sm protein 12 (LSM12). In contrast to LSM12, JPT2 is predicted to be an intrinsically disordered protein, a feature confirmed by circular dichroism and NMR spectroscopy. Under conditions of low Na+ concentration or molecular crowding, JPT2 underwent phase separation, as demonstrated by multiple orthogonal approaches. JPT2 condensates displayed liquid-like behavior and efficiently recruited LSM12, a novel fluorescent NAADP analog, as well as tubulin. JPT2 condensates also interacted with polymerized microtubules and lysosomes isolated from human cell lines. These findings reveal an unexpected capability of NAADP-BPs to undergo phase separation, and segregate with components needed for NAADP-dependent Ca2+ release. We speculate that these signaling condensates dictate cellular NAADP sensitivity, desensitization of NAADP responses, as well as NAADP targeting to TPCs at membrane contact sites between acidic organelles and the endoplasmic reticulum. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=159 SRC="FIGDIR/small/698830v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@108ebc4org.highwire.dtl.DTLVardef@ae9eb9org.highwire.dtl.DTLVardef@36b859org.highwire.dtl.DTLVardef@81053a_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2024

Micromolar fluoride contamination arising from glass NMR tubes and a simple solution for biomolecular applications

Fluorine (19F) NMR is emerging as an invaluable analytical technique in chemistry, biochemistry, material science, and medicine, especially due to the inherent rarity of naturally occurring fluorine in biological, organic, and inorganic compounds. Thus, we were surprised to identify an unexpected peak in our 19F NMR spectra, corresponding to free fluoride, which appears to leach out from various types of new and unused glass NMR tubes over the course of several hours. We quantified this contaminant to be at micromolar concentrations for typical NMR sample volumes across multiple glass types and brands. We find that this artefact is undetectable for samples prepared in quartz NMR tubes within the timeframes of our experiments. We also observed that pre-soaking new glass NMR tubes combined with rinsing removes this contamination below micromolar levels. Given the increasing popularity of 19F NMR across a wide range of fields, the long collection times required for relaxation studies and samples of low concentrations, and the importance of avoiding contamination in all NMR experiments, we anticipate that our simple solution will be useful to biomolecular NMR spectroscopists.

biochemistry↗

bioRxiv2023

Palmitic acid reduces viability and increases production of reactive oxygen species and respiration in rat tendon-derived cells

Clinically, there is a positive correlation between BMI and the risk of tendinopathy. However, the underlying mechanisms are not understood. Dyslipidaemia and increased circulating free fatty acids (FFA) are associated with increased BMI. We hypothesised that increased FFA concentrations negatively affect rat tendon-derived cells (rTDCs) through mitochondrial-mediated mechanisms. rTDCs were isolated and treated with oleic acid (OA), stearic acid (SA), and palmitic acid (PA). Cell viability was assessed using AlamarBlue assay, and gene expression using real-time PCR. Cell respiration and reactive oxygen species (ROS) production were measured using high-resolution respirometry and MitoSox staining. PA transport into the mitochondria was blocked by pre-treatment with 50{micro}M etomoxir. Treatment with SA and PA at 10 {micro}g/ml decreased rTDC viability by 40% and 60%, respectively. PA decreased the gene expression of the tendon markers Scx and Tnmd, and increased the expression of Mmp3, Mmp13, and Ptgs2 (encoding Cox-2). FFA treatment increased the expression of Cpt1 and Pdk4, indicating an increase in mitochondrial FFA oxidation. PA, at 10 {micro}g/ml, increased cellular respiration and ROS production. Pre-treatment with etomoxir partially inhibited the effects of PA on cell viability, Mmp3 gene expression, ROS production, and cell respiration, but did not affect PA-induced inhibition of Scx or Tnmd expression. We found that increased saturated FFA concentrations in the microenvironment reduce cell viability and alter ROS production, respiration, and gene expression. Blocking PA transport into mitochondria partially reversed the negative effects of PA. Overall, an increase in saturated FFA concentrations may contribute to poor tendon health.

cell biology↗

bioRxiv2019

The vagus nerve mediates the suppressing effects of peripherally administered oxytocin on methamphetamine self-administration and seeking in rats

BackgroundThe neuropeptide oxytocin has emerged as a promising pharmacotherapy for methamphetamine (METH) addiction, and clinical trials of intranasal oxytocin are underway. However, there is debate as to how peripherally administered oxytocin alters brain signaling to modulate addiction processes. Interestingly, there is evidence for functional interactions between peripheral oxytocin administration and the vagus nerve. Therefore, this study investigated whether the effects of peripherally administered oxytocin require vagal signaling to reduce METH self-administration and reinstatement of METH-seeking behaviours. MethodsMale and female Sprague-Dawley rats underwent surgery for jugular catheterization and either subdiaphragmatic vagotomy (SDV) or a sham operation. Rats were trained to self-administer METH, and the effect of peripherally administered oxytocin on METH intake was assessed. Rats then underwent extinction, and effects of oxytocin were assessed on cue- and METH-induced reinstatement of METH-seeking. ResultsOxytocin treatment robustly attenuated METH intake in both sexes. Strikingly, SDV entirely prevented the suppressant effect of oxytocin (0.3 mg/kg) on METH intake, and partially prevented the effects of 1 mg/kg oxytocin in both sexes. After extinction, SDV impaired the suppressing effects of oxytocin on cue- and METH-primed reinstatement in males, but not females. SDV was functionally confirmed by measuring food intake following administration of the vagal dependent peptide, cholecyostokin-8. ConclusionOur data suggest that vagus nerve signaling is required for the anti-addiction effects of peripherally administered oxytocin, and that this vagal dependency is partially mediated by sex and drug withdrawal. This study has considerable implications for the applicability of oxytocin as a therapy for METH use disorder for both sexes.

neuroscience↗