Richardson, M. E. S. | Search bioRxiv

bioRxiv2025

Developmental, time-of-day, and stimulus-specific Golgi-Cox staining patterns detected in the mouse brain

Well-coordinated brain activity is a crucial driver of bodily functions and is refined by environmental input. Understanding the structure of brain areas that regulate various functions and how the environment affects the neural responses in the brain has been fundamental in advancing the field of neuroscience and medicine. The Golgi-Cox method is a histological approach that has allowed researchers to view neuronal structures with unmatched and detailed resolution, allowing for the comparison between non-diseased and diseased models, for instance. However, this method is known to stain neurons sparsely, which is useful for distinguishing structural components, but unpredictably, which is difficult for reproducibility and targeted studies. Here, we use three approaches to demonstrate a predictable pattern of cell staining using the Golgi-Cox method. We show that neuronal maturity, time of day, and response to environmental stimuli affect the number of cells stained by the Golgi-Cox method. Furthermore, we found low variability within each experimental group, which indicates staining reproducibility under controlled environments. Our study highlights important parameters for using the Golgi-Cox method and demonstrates its feasibility for broader application in answering neuroscience-based questions. SummaryOur study provides previously unknown insights demonstrating that the historical Golgi-Cox staining pattern of neurons is specifically linked to age, time-of-day, and light-responsiveness at night in the mouse brain.

neuroscience↗

bioRxiv2023

A mouse model for environmentally induced and reversible circadian arrhythmia using gradual exposure to a fragmented day-night cycle

Arrhythmia is considered the most disrupted state of the biological circadian clock, and usually occurs when circadian regulatory genes are rendered non-functional, or the master clock (Suprachiasmatic Nucleus) is ablated. Since clock gene expression is aligned by the external solar day-night cycle to exhibit a 24-hour rhythm, we hypothesized that ill-timed light and dark exposure could negatively impact endogenous circadian clock function in mice. In this study, we present an environmentally driven approach to induce arrhythmia in mice that is also reversible. Using the previously characterized fragmented day-night cycle (FDN) where the 8-hour night is split into four 2-hour fragments and equally distributed across the 24-hour day, we show that mice gradually exposed to the FDN for 1 month lose their circadian rhythmicity. Furthermore, subsequent exposure to constant light or constant dark conditions does not yield typical circadian rhythms, but instead, reveals circadian arrhythmia. Finally, we show that the arrhythmic locomotion phenotype is reversible with one week of reintroduction to a 12 hr day-12 hr night cycle. This is the first study to show how the light-dark environment induces arrhythmia of an intact circadian clock and how it can be reversed.

neuroscience↗