Biology subjects

Barrow, J. C.

Publications and source records attributed to Barrow, J. C..

9 recordsLinked to original sources

bioRxiv2025

Development of a Novel Benzodiazepine to Delineate Peripheral GABA-A Signaling Mechanisms in Visceral Pain Syndromes

Background and AimsVisceral pain is a cardinal symptom of many disorders affecting the gut. Modulators of gamma-aminobutyric acid (GABA) such as benzodiazepines may attenuate colonic pain but the specific contribution of peripheral GABAA receptors remains unclear as these agents have prominent central effects. MethodsUsing medicinal chemistry optimization of the benzodiazepine scaffold, we developed a novel and potent benzodiazepine-based positive allosteric modulator (PAM) of GABAA receptors, Li633, with no significant central nervous system (CNS) penetration. ResultsThe locomotor activity of rats placed in an open field was unchanged with Li633 at doses up to 30 mg/kg, confirming its lack of a CNS effect. LI-633 produced robust potentiation of GABA-induced inward current, with EC50 values ranging from 8 nM (5{beta}2{gamma}2) to 128 nM (3{beta}2{gamma}2). In vitro electrophysiological studies confirmed its ability to reduce excitability of human dorsal root ganglion (DRG) neurons. LI-633 potentiated muscimol-induced GABAergic currents in rat DRG neurons in a dose-dependent manner, with an EC50 of 70.4 nM. In vivo, LI-633 significantly attenuated visceral hypersensitivity and pain behavior in a rat model of irritable bowel syndrome (IBS) and functional dyspepsia (FD). In the IBS model, administration of the drug also resulted in decreased excitability of colon-specific DRG neurons and significantly reduced the colonic afferent response to balloon distention as measured by recordings of neural activity in dorsal ganglia rootlets. ConclusionsThese findings highlight the potential of targeting peripheral GABAA receptors for pain management in IBS and other disorders associated with visceral hypersensitivity.

neuroscience↗

bioRxiv2024

Ribosomal RNA transcription governs splicing through ribosomal protein RPL22

Ribosome biosynthesis is a cancer vulnerability executed by targeting RNA polymerase I (Pol I) transcription. We developed advanced, specific Pol I inhibitors to identify drivers of this sensitivity. By integrating multi-omics features and drug sensitivity data from a large cancer cell panel, we discovered that RPL22 frameshift mutation conferred Pol I inhibitor sensitivity in microsatellite instable cancers. Mechanistically, RPL22 directly interacts with 28S rRNA and mRNA splice junctions, functioning as a splicing regulator. RPL22 deficiency, intensified by 28S rRNA sequestration, promoted the splicing of its paralog RPL22L1 and p53 negative regulator MDM4. Chemical and genetic inhibition of rRNA synthesis broadly remodeled mRNA splicing controlling hundreds of targets. Strikingly, RPL22-dependent alternative splicing was reversed by Pol I inhibition revealing a ribotoxic stress-initiated tumor suppressive pathway. We identify a mechanism that robustly connects rRNA synthesis activity to splicing and reveals their coordination by ribosomal protein RPL22.

molecular biology↗

bioRxiv2021

Stimulus degradation impairs performance in a rodent continuous performance test

Sustained attention is a core cognitive domain that is often disrupted in neuropsychiatric disorders. Continuous performance tests (CPTs) are the most common clinical assay of sustained attention. In CPTs, participants produce a behavioral response to target stimuli and refrain from responding to non-target stimuli. Performance in CPTs is measured as the ability to discriminate between targets and non-targets. Rodent versions of CPTs (rCPT) have been developed and validated with both anatomical and pharmacological studies, providing a translational platform for understanding the neurobiology of sustained attention. In human studies, using degraded stimuli (decreased contrast) in CPTs impairs performance and patients with schizophrenia experience a larger decrease in performance compared to healthy controls. In this study, we tested multiple levels of stimulus degradation in a touchscreen version of the CPT in mice. We found that stimulus degradation significantly decreased performance in both males and females. The changes in performance consisted of a decrease in stimulus discrimination, measured as d, and increases in hit reaction time and reaction time variability. These findings are in line with the effects of stimulus degradation in human studies. Overall, female mice demonstrated a more liberal response strategy than males, but response strategy was not affected by stimulus degradation. These data extend the utility of the mouse CPT by demonstrating that stimulus degradation produces equivalent behavioral responses in mice and humans. Therefore, the degraded stimuli rCPT has high translational value as a preclinical assay of sustained attention.

neuroscience↗

bioRxiv2021

Post-weaning social isolation modulates reward-seeking behavior in a sex-specific manner in mice

Social isolation is a growing concern in public health. Although isolation at any age is harmful, previous studies have shown that isolation during adolescence, correlating with critical periods of brain development, can impair cognitive function and increase the risk for psychiatric illness later in life. In this study, we utilized a mouse model of adolescent social isolation (SI) and compared performance of isolated and group-housed mice on touchscreen-based continuous performance test (CPT) and fixed ratio/progressive ratio (FR/PR) tasks in adulthood. SI increased sensitivity in the CPT in male mice and had no effect in female mice. The increase in sensitivity was consistent across time bins within the 45-minute testing session and there were no SI effects on reaction times or reward retrieval latencies. A possible confound for performance in the CPT would be SI-induced changes in reward-seeking or motivation for the strawberry milk reward. We next compared the SI mice to their group-housed littermate controls on both FR and PR schedules of reinforcement and found that male SI mice earned significantly more reinforcers on FR schedules of reinforcement and had higher breakpoints on PR schedules compared to their group-housed littermates. SI had no effect on FR or PR performance in female mice. These data indicate that SI during adolescence has striking, sex-specific effects on reward-seeking behavior in adult mice and may provide a useful behavioral model for studying the link between SI and risk for neuropsychiatric disorders.

neuroscience↗

bioRxiv2020

Post-weaning social isolation increases ΔFosB/FosB protein expression in the prefrontal cortex and hippocampus in mice

Social isolation is a growing public health concern across the lifespan. Specifically, isolation early in life, during critical periods of brain development, increases the risk of psychiatric disorders later in life. Previous studies of isolation models in mice have shown distinct neurological abnormalities in various regions of the brain, but the mechanism linking the experience of isolation to these phenotypes is unclear. In this study, we show that {Delta}FosB, a long-lived transcription factor associated with chronic stress responses and drug-induced neuroplasticity, is upregulated in the medial prefrontal cortex and hippocampus of adult C57BL/6J mice isolated for two weeks post-weaning. Additionally, a related transcription factor, FosB, is also increased in the medial prefrontal cortex in socially isolated females. These results show that short-term isolation during the critical post-weaning period has long-lasting and sex-dependent effects on gene expression in brain.

neuroscience↗

bioRxiv2020

Effects of catechol-O-methyltransferase inhibition on effort-related choice behavior in male mice

Effort-related choice (ERC) tasks allow animals to choose between high-value reinforcers that require high effort to obtain or low-value/low-effort reinforcers. Dopaminergic neuromodulation regulates effort-related choice behavior. The enzyme catechol-O-methyltransferase (COMT) metabolizes synaptically-released dopamine. COMT is the predominate regulator of dopamine turnover in regions of the brain with low levels of dopamine transporters, including the prefrontal cortex. Here, we evaluated the effects of the COMT inhibitor tolcapone on ERC performance in a touchscreen-based fixed-ratio/concurrent chow assay in male mice. In this task, mice were given the choice between engaging in a fixed number of instrumental responses to acquire a strawberry milk reward and consuming standard lab chow concurrently available on the chamber floor. We found no significant effects of tolcapone treatment on either strawberry milk earned or chow consumed compared to vehicle treatment. In contrast, we found that haloperidol decreased instrumental responding for strawberry milk and increased chow consumption as seen in previously published studies. These data suggest that COMT inhibition does not significantly affect effort-related decision making in a fixed-ratio/concurrent chow task in male mice.

neuroscience↗

bioRxiv2019

Development of a PC12 cell-based assay for in vitro screening of catechol-O-methyltransferase inhibitors

The male rat adrenal pheochromocytoma cell-originated PC12 cell line can synthesize and release catecholamine neurotransmitters, and it has been widely used as a model system in cell biology and toxicology research. Catechol-O-methyltransferase (COMT) is involved in the inactivation of the catecholamine neurotransmitters, and it is particularly important for theregulation of dopamine. In this study, we explored the feasibility of using PC12 cells as an in vitro drug screening platform to compare the activity of multiple COMT inhibitors. Incubation of PC12 cells with tolcapone, a highly potent and selective COMT inhibitor, increased the concentrations of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) while reducing the metabolites 3-methoxytyramine (3-MT) and homovanillic acid (HVA) in the cell culture medium. LIBD-3, a novel, non-nitrocatechol COMT inhibitor produced similar effects compared to tolcapone. LIBD-4, a less potent inhibitor, exhibited the expected right-shift in functional inhibition in the assay. These results match the known in vivo effects of COMT inhibition in rodents. Together, these data support the continued use of PC12 cells as an in vitro screen that bridges cell-free enzyme assays and more costly in vivo assays.

neuroscience↗

bioRxiv2019

Novel, non-nitrocatechol COMT inhibitors modulate dopamine neurotransmission in the frontal cortex and improve cognitive flexibility

Cognitive impairment is a primary feature of many neuropsychiatric disorders and there is a need for new therapeutic options. Catechol-O-methyltransferase (COMT) inhibitors modulate cortical dopaminergic function and have been proposed as potential cognitive enhancers. Unfortunately, currently available COMT inhibitors are not good candidates due to either poor blood-brain barrier penetration or severe toxicity. To address the need for safe, brain-penetrant COMT inhibitors, we tested multiple novel COMT inhibitors in a set of preclinical in vivo efficacy assays to determine their viability as potential clinical candidates. We found that multiple COMT inhibitors, exemplified by LIBD-1 and LIBD-3, significantly modulated dopaminergic function measured as decreases in homovanillic acid (HVA) and increases in 3,4-Dihydroxyphenylacetic acid (DOPAC), two dopamine metabolites, in cerebrospinal fluid (CSF) and the frontal cortex. Additionally, we found the LIBD-1 significantly improved cognitive flexibility in a rat attentional set-shifting assay (ASST), an effect previously seen with the COMT inhibitor tolcapone. These results demonstrate that LIBD-1 is a novel COMT inhibitor with promising in vivo activity and the potential to serve as a new therapy for cognitive impairment.

neuroscience↗

bioRxiv2018

Dissecting transcriptomic signatures of neuronal differentiation and maturation using iPSCs

Human induced pluripotent stem cells (hiPSCs) are a powerful model of neural differentiation and maturation. We present a hiPSC transcriptomics resource on corticogenesis from 5 iPSC donor and 13 subclonal lines across nine time points over 5 broad conditions: self-renewal, early neuronal differentiation, neural precursor cells (NPCs), assembled rosettes, and differentiated neuronal cells that were validated using electrophysiology. We identified widespread changes in the expression of individual transcript features and their splice variants, gene networks, and global patterns of transcription. We next demonstrated that co-culturing human NPCs with rodent astrocytes resulted in mutually synergistic maturation, and that cell type-specific expression data can be extracted using only sequencing read alignments without potentially disruptive cell sorting. We lastly developed and validated a computational tool to estimate the relative neuronal maturity of iPSC-derived neuronal cultures and human brain tissue, which were maturationally heterogeneous but contained subsets of cells most akin to adult human neurons.

genomics↗