Separation of Short- and Medium-Chain Fatty Acids Using Capillary Electrophoresis With Indirect Photometric Detection: Part II: Validation of Endogenous Concentration in Rat Feces

As a public health crisis, cocaine addiction has no lasting treatments to prevent relapses, and adolescent behavior has been linked to risky behavior, including drug use. Addiction treatment may benefit from targeting the gut–brain axis. Short- and medium-chain fatty acids (SMCFAs) are produced by bacteria in the gut and communicate with the brain, therefore influencing drug reinforcement. The study has three primary objectives. To obtain dried feces, a simple, efficient desiccation time is first optimized. Second, we examined the analytical figures of merit for method validation to establish selectivity, linearity, limit of detection, limit of quantitation, precision, accuracy, matrix effects, and stability. Third, we establish baseline concentrations of SMCFAs (including branched-chain fatty acids) in the feces of healthy adults and adolescent rats. In addition, this study examines whether capillary electrophoresis with indirect photometric detection (IPD) can be used to determine whether antibiotics, cocaine, or both deplete SMCFAs in healthy rats. The results suggest that antibiotic treatment severely reduces fatty acid content in healthy rats, while cocaine exposure causes only modest decline. Therefore, the role of SMCFAs should be investigated as a possible route for gut–brain communication in addiction. To our knowledge, this is the first capillary electrophoresis IPD method that establishes baseline concentrations of fecal SMCFAs in adults and adolescents rats.