The peripheral benzodiazepine receptor (PBR), has been recently shown to play a key role in the regulation of the mitochondrial process leading to apoptosis, which occurs during cardiac ischemia. The present work shows that SSR 180575, a novel PBR ligand of potential interest in pathological cardiovascular indications, irreversibly and specifically binds with high affinity on both rat heart mitochondria and on a cell line transfected with the human PBR (K-d = 1.95 +/- 0.22 and 4.58 +/-0.83 nM, respectively). In conclusion, SSR180575 is a specific and potent PBR ligand which irreversible binding to PBR appears of high interest in various therapeutic indications where apoptosis occurs. (C) 2003 Elsevier Inc. All rights reserved.