Autoradiographic comparison of [I-125]epidepride and [I-125]NCQ 298 binding to human brain extrastriated dopamine receptors

Extrastriatal D-2-dopamine receptors can be visualised in the monkey and human brain using the benzamides [C-11] and [Br-76]FLB 457 in PET and [I-123]epidepride in SPECT but not with the salicylamide analogues [Br-76]FLB 463 and [I-123]NCQ 298. To clarify the background for the differences in binding seen in vivo, we have compared the in vitro binding of [I-125]epidepride and [I-125]NCR 298, using human whole hemisphere autoradiography. The images obtained with any radioligand showed detailed distribution with very dense binding in the putamen and the caudate nucleus and with the same detailed extrastriatal distribution. Thus, the divergent results obtained in vivo cannot be explained by different binding properties of the extrastriatal receptors. (C) 1997 Elsevier Science Inc.