Comparison of in vivo D-2 dopamine receptor binding of IBZM and NMSP in rat brain.

In vivo biodistribution of S- and R-isomers of [125I]IBZM in rats showed a significant initial brain uptake (3.20 and 2.67% dose/organ at 2 min, respectively). The wash-out from the brain was slower for the S-isomer. The striatum to cerebellum ratio for [125I]S-IBZM decreased with an increasing dose of cold carrier or spiperone, suggesting that the brain uptake is stereospecific and saturable, and may be related to the binding of D-2 dopamine receptors. In a dual isotope digital autoradiography study [125I]IBZM and [3H]NMSP(N-methylspiperone) show comparable regional cerebral distribution in rats.