Precise dynamic control of tissue oxygenation during brain slice electrophysiology

Precise oxygen regulation is essential for maintaining neuronal integrity in ex vivo brain slice electrophysiology, yet conventional chambers provide poorly defined oxygenation. This limitation is particularly problematic when model neurological disorders are characterized by transient or intermittent hypoxia (IH), such as transient ischemic attacks and sleep apnea. We aimed to develop a versatile oxyslice recording chamber (ORC), enabling real-time monitoring of neural activity with rapid, precise oxygen modulation during standard recordings. A polydimethylsiloxane (PDMS)-based ORC comprising a gas-permeable membrane that separates the recording and gas chambers was developed, allowing rapid and uniform oxygen exchange. The device integrates seamlessly into standard electrophysiological setups and operates at low perfusion rates. Tissue oxygenation was measured, and hippocampal slices were exposed to continuous hypoxia (CH, 3% or 1% O₂) and IH (6-1% O₂ cycles every 30 s) while recording field excitatory postsynaptic potentials (fEPSPs) in the hippocampal CA1 region. The ORC achieved precise, reproducible control of oxygen at the cellular level. Both CH and IH induced hypoxia severity-dependent reductions in fEPSP slopes, fully reversed upon reoxygenation. Severe CH (1% O₂) reduced the fEPSP slope by ∼60%, whereas IH reduced it by ∼40%, indicating a partial mitigation during reoxygenation phases. This novel ORC provides a robust, adaptable method for real-time oxygen modulation in ex vivo neuronal standard recordings. Its ability to model continuous and intermittent hypoxia at physiological oxygen tensions fills a major gap in current electrophysiological methodologies, opening new opportunities for mechanistic studies of hypoxia-driven dysfunction and therapeutic discovery.<b>NEW & NOTEWORTHY</b> This study presents the oxyslice recording chamber (ORC), a simple and reproducible system for precise oxygen control during brain slice recordings. The ORC has been developed to be easily constructed and implemented in any electrophysiology laboratory. As a proof of concept, we reproduced continuous hypoxia (transient ischemic stroke) and intermittent hypoxia (sleep apnea), revealing distinct and reversible changes in hippocampal function applicable to various hypoxia-related conditions and brain regions.