Measurement of oxidative stress in the rodent brain using computerized electron spin resonance tomography.

The strategy of this study was to improve the electronic spin resonance (ESR) application used to detect free radical-induced oxidative stress in animal models. We have developed an in vivo ESR imaging system with high-quality ESR-computed tomography (CT) images by using a nitroxyl spin probe--BBB-permeable, 3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-yloxy (MC-PROXYL)--in living small animals. We first measured the distribution of MC-PROXYL in the head region of a living mouse by using ESR-CT imaging after treatment with MC-PROXYL. In the ESR-CT experiments, it was clearly observed that MC-PROXYL was well distributed in the brain of head region of a living mouse. The ESR-CT images taken after treatment with MC-PROXYL demonstrate that the decay of MC-PROXYL in the isolated brain of a spontaneously hypertensive rat (SHR) was more rapid than that in a Wister Kyoto rat. ESR-CT analysis revealed that the region of rapid decay might be located in the cerebral cortex of the isolated brain of an SHR. These results suggest that the present study of ESR-CT imaging would be a useful tool for monitoring and detecting the locations of oxidative stress in the brains of rodent animal models.