A radioiodinated 7 alpha-O-iodoallyl diprenorphine for mapping opioid receptors

The aim of the current research has been to validate an original radioiodin ated diprenorphine (DPN) derivative suitable for imaging studies of opioid receptors. [I-125]7 alpha-O-iodoallyl diprenorphine (7 alpha-O-IA-DPN) was prepared by radioiododestannylation and in vitro and in vivo opioid recepto r binding assays were performed with CDF1 mouse brains. In vitro binding studies showed high affinity (K-i = 0.4 +/- 0.2 nM) for mo use brain membranes. In vivo studies showed 63% specific binding. Ex vivo a utoradiography of brain sections confirmed high uptake and retention of [I- 125]7 alpha-O-IA-DPN in regions rich in opioid receptors. This new radioiod inated DPN analogue appears to be a potential radioprobe for in vivo visual ization of human cerebral opioid receptors with single photon emission comp uted tomography (SPECT). (C) 1999 Harcourt Publishers Ltd.