Effect of postmortem delay on imidazoline receptor-binding proteins in human and mouse brain

Immunoreactive proteins of 45-kD and 29/30-kD doublet bands are candidate imidazoline receptor binding proteins (IRBP) based on associations with I(1) or I(2) binding sites, respectively. It was reported that the density of cortical membrane 29/30-kD I(2) protein is diminished whereas a 45-kD I(1) protein is increased in depressed suicide victims versus controls. IRBP immunoreactive bands of similar size have been suggested to be breakdown products of the 170-kD protein known as IRAS (putative full-length I(1) receptor). This study compares nonpathologic human brains collected and frozen after postmortem delays of 13.4 hours +/- 1.7 (SEM) with brains of longer postmortem delays (26.1 hours +/- 1.2). The fresher human brains possessed more full-length IRAS (P = 0.05). In another study, the postmortem decay of IRBP bands in mouse brain was shown to be linear over time. The results are relevant to previous studies of IRBP bands in postmortem brains of depressed suicide victims.