A number of researchers have reported that
free radicals generated in the brain are involved in various brain dysfunctions, including
ischemia-reperfusion injury,
brain tumors, and
neurodegenerative diseases. It has been reported that the spin probe
MC-PROXYL can penetrate the blood-brain barrier and can be useful for evaluating oxidative stress in the brain. Preliminary comparisons were made by ESR imaging of the heads of live mice and isolated rat brains using the spin probe
MC-PROXYL and the blood-brain-barrier impermeable probe carbamoyl-PROXYL. The results showed that
MC-PROXYL, but not carbamoyl-PROXYL, was widely distributed in the brain. These methods were also applied for the imaging of brains from
stroke-prone spontaneously hypertensive rats (SHRSPs). The rapid decay of 2D ESR images of
MC-PROXYL in isolated SHRSP-brain was observed, compared to Wistar-Kyoto rats (WKYs), using the ESR imaging system. Furthermore, we provide evidence, by using L-band ESR non-invasively, that the decay rate of
MC-PROXYL in the head region is faster in live SHRSPs than in live WKYs. Taken together, the high oxidative stress sustained by
oxygen radical generation in SHRSPs may cause the alteration of
MC-PROXYL metabolism in the brain. Our results suggest that in vivo ESR could be applied to the assessment of
antioxidant effects on oxidative stress in the brain in
animal disease models, such as the SHRSP.