Imaging Dopamine Receptors in the Rat Striatum with the MicroPET R4: Kinetic Analysis of [11C]Raclopride Binding Using Graphical Methods

This chapter describes the binding potential computed for 15 [11C]raclopride studies in the rat striatum using the micro-PET R4. In two of these studies, a 1-mg/kg blocking dose of raclopride was coadministered with the tracer to measure nonspecific binding of the tracer. The remaining studies were carried out with varying doses of [11C]raclopride of varying specific activity. Data are summarized as the binding potential as a function of raclopride mass injected. The curve is the best fit to a single-site ligand receptor model allowing for fitting of the modified equilibrium constants. Image data were corrected for spillover from the intraorbital lachrymal glands but were not corrected for partial volume averaging. The microPET R4, with a FWHM resolution is expected to give a truer measure of striatal [11C]raclopride concentration, and therefore, gives a larger binding potential. Determinations of binding potential using the graphical method were compared with the values obtained using a compartmental model without blood sampling. The results support the use of the noninvasive graphical analysis methodology with [11C]raclopride, and the microPET R4 to measure dopamine receptor availability in the rat striatum.