Biology subjects

Brandon, J. M.

Publications and source records attributed to Brandon, J. M..

4 recordsLinked to original sources

bioRxiv2026

Chronic lower limb pain is not associated with a loss of inhibitory neurons in the human lumbar spinal dorsal horn

The spinal dorsal horn is the primary processing site of nociceptive sensory input from the periphery. Excitatory spinal interneurons releasing glutamate can amplify this information before it is sent to the brain, whereas inhibitory neurons releasing GABA and/or glycine can suppress the outflow of nociceptive signals. An imbalance favoring excitation is thought to underlie certain aspects of chronic pain. Although rodent studies have identified spinal mechanisms underlying hyperalgesia and allodynia, little is known about the anatomical changes associated with chronic pain in the human spinal cord, a gap in knowledge we sought to address in this study. Using immunohistochemistry and in situ hybridization on lumbar spinal cord tissue recovered from organ donors, we characterized neuronal size and density across the human dorsal horn and confirmed the presence of the human equivalent of the lateral spinal nucleus in many individuals. Chronic lower limb pain was not associated with changes in neuronal density in the dorsal horn. Likewise, the ratio of excitatory (SLC17A6+) to inhibitory (PAX2+) neurons remained consistent across laminae for age, sex and chronic pain state, providing no evidence for selective loss of inhibitory neurons with chronic pain in humans. We found no differences in the size or density of the postsynaptic markers Homer1 and gephyrin between groups, suggesting glutamatergic and GABAergic postsynaptic sites remain structurally stable. These findings provide a thorough evaluation of cellular anatomy of the human dorsal horn and form a foundation for future studies investigating neuronal changes that may contribute to chronic pain in humans.

neuroscience↗

bioRxiv2026

Antibiotics modulate activity of mouse and human dorsal root ganglia neurons

Antibiotics are among the most prescribed medications worldwide, yet their direct effects on eukaryotic tissues remain largely unexplored. Here, we used in vitro calcium imaging to determine if clinically relevant concentrations of common antibiotics alter mouse and human dorsal root ganglion (DRG) neuron activity. We found that {beta}-lactams, macrolides, and tetracyclines induce calcium flux in sensory neurons within minutes of application. Regardless of antibiotic class, neuronal responses depend on extracellular calcium entry. Pharmacological manipulations further revealed that cephalexin responses depend on TRPA1 activity whereas doxycycline responses require mitochondrial reactive oxygen species (ROS) production. These findings demonstrate that clinically relevant concentrations of antibiotics directly modulate sensory neuron activity through divergent mechanisms, thus expanding our current understanding of antibiotic side effects.

neuroscience↗

bioRxiv2026

T-cell distribution in the dorsal root ganglion across species, sex, and age

T-cells infiltrate somatosensory ganglia in response to nerve damage, autoimmune disease, and infection, contributing to sensory abnormalities and pain. In naive states, T-cells are rare in the rodent dorsal root ganglion (DRG) but have been reported in human and non-human primates without known relevant exposures. It remains unclear whether there are inherent evolutionary or species differences in DRG T-cell residence. Using a comparative biology approach, we investigated the frequency and distribution of T-cells in the mammalian DRG across humans, non-human primates, pigs, and rodents, and in humans investigated the contributions of sex and age. Spatial transcriptomics and immunofluorescence independently verified the robust presence of DRG T-cells at similar levels in humans, non-human primates, and pigs, but were fewer in rats and largely absent in mice. In humans, premenopausal females were more likely to have elevated DRG endoneurial T-cells than post-menopausal females or adult males. T-cells were detected in human dorsal root ganglion at as early as two months of age but were less abundant within the perineuronal niche. Most human DRG T-cells expressed distinct markers consistent with a resident memory (Trm) phenotype. We discuss the importance of studying the functional roles of DRG-resident T-cells and raise broader considerations for modelling peripheral nervous system disease.

neuroscience↗

bioRxiv2025

A molecular map of the human spinal dorsal and ventral horn defines arrangement of neuronal types and glial sex differences

The spinal cord is the gateway for somatosensory and nociceptive information to the brain and a key locus for sensory-motor integration. Studies in mice have advanced our understanding of spinal cord circuitry, and transcriptomic studies have begun to characterize the human spinal cord; however, major gaps in knowledge persist. We conducted single-nucleus sequencing of lumbar spinal cord tissue from 11 adult organ donors and annotated spinal cord cell types with high resolution spatial transcriptomics. We identified 34 spatially and transcriptionally defined neuronal classes and detected sex-specific cell types and states across multiple glial populations. Electrophysiological recordings from dorsal horn neurons revealed firing patterns for neuronal subtypes and group I mGluR-dependent plasticity. Our work defines previously unknown aspects of human spinal cord molecular anatomy and physiology.

neuroscience↗