PROLACTIN PLASMA-LEVELS AND D-2-DOPAMINE RECEPTOR OCCUPANCY MEASURED WITH IBZM-SPECT

By the application of (123)([I-123]IBZM), an iodine-labelled dopamine D-2-receptor antagonist, brain D-2 receptors in humans can be visualiz ed with single photon emission computed tomography (SPECT). The ratio of IBZM binding to striatal regions versus binding to frontal cortex ( ST/FC ratio) provided a semiquantitative measurement of D-2 receptor b inding in the striatum. This study investigated the relationship betwe en receptor occupancy and plasma prolactin levels in 12 male patients treated with haloperidol, benperidol or clozapine. Prolactin levels we re positively correlated with D-2 receptor occupancy, reflecting at le ast in part a comparable dopamine receptor antagonism in different dop aminergic pathways.