Blocking Studies Using Storage Phosphor Imaging. To determine whether [[sup.123]I]-1 binds selectively to [D.sub.2/3] receptors in vivo, in the following experiments 5 rats received an i.v.
was chosen as time point to sacrifice the rats during the subsequent storage phosphor imaging experiment (see Tables 1 and 2 and Figure 1).
In the storage phosphor imaging experiments, no specific striatal binding was observed for [[sup.123]I]-1 (Figure 2).
However in the storage phosphor imaging experiments it appeared that no binding in the striatum was blocked by the dopamine receptor antagonist haloperidol, suggesting absence of specific displaceable binding to dopamine [D.sub.2/3] receptor.
In the storage phosphor imaging studies it was shown that [[sup.123]I]-1 binds to white matter, which suggests that the tracer has a relatively high lipophilicity.
Particularly, the performed biodistribution studies suggested higher binding in the [D.sub.2/3] receptor-rich striatum than in brain areas devoid of [D.sub.2/3] receptors, while the final storage phosphor imaging studies showed no selective binding of [[sup.123]I]-1 to central [D.sub.2/3] receptors in rats.