Characterization of local pH changes in brain using fast-scan cyclic voltammetry with carbon microelectrodes
Pavel Takmakov1, Matthew K Zachek, Richard B Keithley
1Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
Analytical Chemistry
|November 5, 2010
Summary
This study clarifies pH measurement in the brain using fast-scan cyclic voltammetry (FSCV). Researchers identified capacitive peaks and the influence of brain compounds like DOPAC, improving in vivo pH monitoring.
Area of Science:
- Neuroscience
- Electrochemistry
- Biomedical Engineering
Background:
- Transient brain pH changes reflect neural activity and metabolic processes crucial for behavior, learning, and memory.
- Existing methods lack the temporal resolution needed to measure pH fluctuations in freely moving animals.
- Fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes has been used for pH transient measurement, but the origin of its signals in vivo was unclear.
Purpose of the Study:
- To elucidate the origin of potential-dependent currents in in vivo pH cyclic voltammograms (CVs) using FSCV.
- To identify factors causing discrepancies between in vivo and in vitro pH CV data.
- To validate the performance of carbon-fiber sensors for in vivo brain pH monitoring.
Main Methods:
- Investigated the nature of peaks in pH CVs recorded in vivo.
- Examined the effect of electrochemically inert species (aromatic amines, calcium) on pH CV signals.
- Identified the contribution of 3,4-dihydroxyacetic acid (DOPAC) to in vivo pH CVs.
- Induced brain acidosis in anesthetized rats via hypercapnia (carbon dioxide inhalation) to test sensor performance.
Main Results:
- Identified a peak related to the capacitive nature of the pH CV.
- Demonstrated that adsorption of inert species can suppress this capacitive peak, explaining in vivo/in vitro data inconsistencies.
- Discovered an additional peak in vivo pH CVs attributable to the presence of DOPAC.
- Confirmed that hypercapnia reliably induces significant in vivo pH changes, validating the FSCV pH signal.
Conclusions:
- The study clarifies the electrochemical basis of in vivo pH measurements using FSCV.
- Understanding signal origins and interfering substances (e.g., DOPAC, inert species) is crucial for accurate brain pH monitoring.
- Hypercapnia serves as an effective method for validating in vivo pH sensor performance and inducing robust pH changes.
Related Concept Videos
01:10Voltammetric Techniques: Cyclic Voltammetry
Cyclic voltammetry (CV) is an electrochemical technique used to investigate the redox properties of a chemical species. It involves measuring the current response of an electrochemical cell as a function of the applied potential. The setup for cyclic voltammetry typically consists of a working electrode, a reference electrode, and a counter electrode—all immersed in an electrolyte solution. The working electrode is where the redox reaction of interest occurs, while the reference electrode...
01:12Voltammetric Techniques: Linear-Scan (E vs Time)
Polarography is a classical voltammetric technique used to analyze electrochemical reactions. This method applies a linear potential sweep to a dropping mercury electrode (DME), and the resulting current is measured. A dropping mercury electrode is commonly used as the working electrode in polarography. It consists of a capillary tube filled with mercury, where the tiny droplet forms at the tip. This droplet continuously drops from the capillary, creating a new electrode surface for each...