Platelet I1-imidazoline binding sites are decreased by two dissimilar antidepressant agents in depressed patients

Platelet imidazoline receptors as state marker of depressive symptomatology

“…Previous studies have shown that IR-1 are increased in frontal cortex and platelets of depressed patients (Garcia-Sevilla et al, 1996;Piletz et al, 2003a;Piletz, Halaris, Nelson, Qu, & Bari, 1996a;Piletz, Halaris, Saran, & Marler, 1991;Piletz, Halaris, Chikkala, & Qu, 1996b;Piletz, Schubert, & Halaris, 1986), and this up-regulation is normalized (down-regulated) after antidepressant drug treatments (Garcia-Sevilla et al, 1996;Piletz et al, 1991;Piletz et al, 1996b;Zhu et al, 1999;Zhu, Halaris, & Piletz, 1997). In two western blotting studies, the immunoreactivity of IRAS in 33 kD and 45 kD bands (peptides of IRAS (Zhu, Hayes, Chen, Baldwin, & Piletz, 2003a) was increased in platelets and prefrontal cortical membranes (Garcia-Sevilla et al, 1996) but decreased in hippocampal homogenates (Piletz et al, 2000b) from depressed patients relative to matched controls.…”

“…These were suspended in 3.0 ml ice-cold buffer containing 1 mM Pefabloc (Sigma) and homogenized at 9,000 rpm for 1 min (30 sec twice) with a tissue-mizer. The sample was then centrifuged at 100,000 × g for 60 min at 4°C, washed in 6.0 ml of 5.0 mM Hepes, 0.5 mM MgCL 2 , 0.5 mM EGTA, pH 7.4 (HME) buffer with 1 mM Pefabloc, centrifuged again at 100,000 × g for 60 min, followed by resuspension in 0.5 ml HME buffer (Ernsberger, Piletz, Graff, & Graves, 1995b;Piletz et al, 1996b;Piletz & Sletten, 1993). Using this preparation, the radioligand binding assays were done in batches on different days.…”

“…Radioligand binding was performed according to a previously described glass fiber filtration procedure (Ernsberger et al, 1995b;Piletz et al, 1996b;Piletz et al, 1993). Binding assays were performed at a single concentration of 8 nM p-[ 125 I]clonidine (New England Nuclear).…”

“…To ensure this, six pre/post-treatment pairs of platelet samples were retrieved from which Bmax values were already known from a previous study (Piletz et al, 1996b). These six samples -herein called "depression controls" -were taken from the frozen (−80°C) supply of a previous study (Piletz et al, 1996b) which had shown platelet IR-1 down-regulation after desipramine treatment (Piletz et al, 1996b).…”

“…Desipramine, a norepinephrine (NE) reuptake inhibitor type antidepressant, was administered for six weeks to 12 healthy human subjects in order to simulate the length of time and dosing used to obtain a therapeutic response in depressed patients (Piletz et al, 1996b). Plasma concentrations of desipramine were measured throughout the six weeks of treatment and again after 2 weeks following discontinuation of treatment.…”