Abstract
BackgroundCarbon dioxide overdose is frequently used to cull rodents for tissue harvesting. However, this treatment may lead to respiratory acidosis, which potentially could change the properties of the investigated tissue. New methodMechanical tissue properties often change in pathological conditions and may thus offer a sensitive generic readout for changes in biological tissues with clinical relevance. In this study, we performed force-indentation measurements with an atomic force microscope on acute cerebellar slices from adult rats to test if brain tissue undergoes changes following overexposure to CO2 compared to other methods of euthanasia. ResultsThe pH significantly decreased in brain tissue of animals exposed to CO2. Concomitant with the drop in pH, cerebellar grey matter significantly stiffened. Tissue stiffening was reproduced by incubation of acute cerebellar slices in acidic medium. Comparison with existing methodsTissue stiffness provides an early, generic indicator for pathophysiological changes in the CNS. Atomic force microscopy offers unprecedented high spatial resolution to detect such changes. ConclusionsOur results indicate that the stiffness particularly of grey matter strongly correlates with changes of the pH in the cerebellum. Furthermore, the method of tissue harvesting and preparation may not only change tissue stiffness but very likely also other physiologically relevant parameters, highlighting the importance of appropriate sample preparation.
Highlights
Brain tissue is very sensitive to environmental changes, and to a lack of oxygen
Since overexposure of CO2 – but not the other methods – leads to a respiratory acidosis and increases blood acidity, we first tested if the pH of brain tissue changes
The pH trace from animals culled by an overdose of anesthetic overlapped with that of decapitated animals (p = 0.92), indicating that the decrease in tissue pH after CO2 overdose was caused by respiratory acidosis rather than by the time course of the treatment
Summary
Brain tissue is very sensitive to environmental changes, and to a lack of oxygen. CO2 overdose, which is a standard method to cull rodents for tissue harvesting, leads to an impairment. Of the oxygen-carbon dioxide exchange, causing death by asphyxiation It overloads the capacity of the physiological pH bicarbonate buffering system within the body. Carbon dioxide overdose is frequently used to cull rodents for tissue harvesting. This treatment may lead to respiratory acidosis, which potentially could change the properties of the investigated tissue. The method of tissue harvesting and preparation may change tissue stiffness but very likely other physiologically relevant parameters, highlighting the importance of appropriate sample preparation
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