No abstract

Summary: Equilibrium models are derived and applied to in vivo binding of spiperone in the rat brain. The models express the concentration of the ligand in the striatum and frontal cortex as a function of the accumulation in the cerebellum. The models differ with respect to the descrip tion of specific binding. Nonlinear regression analysis shows that the in vivo specific binding of 3H-Iabeled spip erone in the frontal cortex (mainly serotonergic) can be described by a noninteracting sites model, whereas the specific binding in the striatum (mainly dopaminergic) can best be described by models that lead to sigmoid satura tion curves. These results were tested and partly con firmed by determining the region-of-interest/cerebellar ra dioactivity ratio of ttC-Iabeled N-methylspiperone, withTo understand the role of dopamine receptors in human brain pathologies and the antipsychotic ac tions of dopamine antagonists, the in vivo charac terization of the dopamine receptor is required. Data obtained from in vitro experiments may not always apply to in vivo situations. The microenvi ronment of the receptor and the affinity and number of available binding sites may be modified during in vitro processing. Recently, such disparities be tween in vivo and in vitro with respect to spiperone