SIC, an intracerebral beta(+)-range-sensitive probe for radiopharmacology investigations in small laboratory animals: Binding studies with C-11-raclopride

Our aim was to show the ability of a recently developed P I range-sensitive intracerebral probe (SIC) to measure, in vivo, the binding of radioligands in small animals. Methods: The potential of the device for pharmacokinetic studies was evaluated by measurement of the dynamic striatal binding of C-11-raclopride, a well-documented D-2 dopaminergic receptor ligand, in rat brain after intravenous injection of the labeled compound. The effects of preinjection of the unlabeled ligand (raclopride, 2 mg/kg intravenously) and of increasing the synaptic dopamine level (amphetamine treatment, 1 mg/kg intravenously) or of depleting synaptic dopamine (reserpine pretreatment, 5 mg/kg intraperitoneally) on in vivo C-11-raclopride binding were monitored by SIC. Results: The radioactivity curves measured as a function of time were reproducible and consistent with previous studies using PET imaging (ratio of striatum to cerebellum, 2.6 +/- 0.3 after 20 min). Further studies showed significant displacement of C-11-raclopride by its stable analog. Finally, the device proved its capacity to accurately detect changes in C-11-raclopride binding after a sudden (amphetamine) or a gradual (reserpine) modulation of endogenous dopamine levels. Conclusion: These results show that the new device can monitor binding of PET ligands in anesthetized rodents in vivo, with high temporal resolution