In vivo electron spin resonance spectroscopy on signal decay of intrastriatal nitroxide radical after acute administration of haloperidol in rats

Sequential changes in the electron spin resonance (ESR) signal intensity of nitroxide radical perfused in the striatum of rats treated with haloperido l (HPD) were evaluated using a 700-MHz ESR spectrometer, Nitroxide radical was perfused in the striatum by in vivo microdialysis. Nitroxide used was 3 -carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl. Following 6-h perfusion o f the nitroxide radical by dialysis at the rate of 2 mu l/min through the r adical introducer that had been stereotaxically implanted in the rat's stri atum, HPD or saline was injected intraperitoneally into the rats in the res onator, The sequential changes in the ESR spectrum of the nitroxide radical were then evaluated. Spectra were successively observed in all animals. Th e half-life, which was estimated on the basis of the exponential decay in s ignal intensity, was used as a parameter of decay rate of the ESR signal in tensity of nitroxide radical. The half-life in the rats injected with HPD w as significantly longer than that in controls, This finding suggests that t he reducing ability of the striatal extracellular space of a rat acutely tr eated with HPD was decreased in comparison with that of the control, (C) 20 00 Elsevier Science Inc.