In vivo temporal EPR imaging of the brain of rats by using two types of blood-brain barrier-permeable nitroxide radicals

In vivo temporal EPR imaging was conducted on the brain of rats that received one of two kinds of blood-brain barrier-permeable nitroxide radicals via the tail vein—one is a water-soluble 3-hydroxymethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (hydroxymethyl-PROXYL); and the other is a non-water-soluble 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (PCAM). From temporal EPR imaging data, temporal changes in the distribution of the nitroxide radical in the cerebral cortex, striatum, and hippocampus in the brain were investigated. It was found that the half-lives of the three parts in the brain of hydroxymethyl-PROXYL are longer and their EPR signal intensities are greater than those of PCAM.