Microelectrode Sensor for Real-Time Measurements of Nitrite in the Living Brain, in the Presence of Ascorbate

The impaired blood flow to the brain causes a decrease in the supply of oxygen that can result in cerebral ischemia; if the blood flow is not restored quickly, neuronal injury or death will occur. Under hypoxic conditions, the production of nitric oxide ((NO)-N-center dot), via the classical L-arginine-(NO)-N-center dot synthase pathway, is reduced, which can compromise (NO)-N-center dot-dependent vasodilation. However, the alternative nitrite (NO2-) reduction to (NO)-N-center dot, under neuronal hypoxia and ischemia conditions, has been viewed as an in vivo storage pool of (NO)-N-center dot, complementing its enzymatic synthesis. Brain research is thus demanding suitable tools to probe nitrite's temporal and spatial dynamics in vivo. In this work, we propose a new method for the real-time measurement of nitrite concentration in the brain extracellular space, using fast-scan cyclic voltammetry (FSCV) and carbon microfiber electrodes as sensing probes. In this way, nitrite was detected anodically and in vitro, in the 5-500 mu M range, in the presence of increasing physiological concentrations of ascorbate (100-500 mu M). These sensors were then tested for real-time and in vivo recordings in the anesthetized rat hippocampus; using fast electrochemical techniques, local and reproducible transients of nitrite oxidation signals were observed, upon pressure ejection of an exogenous nitrite solution into the brain tissue. Nitrite microsensors are thus a valuable tool for investigating the role of this inorganic anion in brain redox signaling.

Automated summary

Impaired blood flow to the brain can lead to cerebral ischemia, resulting in neuronal injury or death. A new method using fast-scan cyclic voltammetry and carbon microfiber electrodes has been proposed for real-time measurement of nitrite concentration in the brain extracellular space, providing valuable insights into the role of this inorganic anion in brain redox signaling.