Effect of bupropion on immunodensity of putative imidazoline receptors on platelets of depressed patients

A substantial number of studies have demonstrated increased imidazoline rec eptors (I-1 binding sites) on platelets of depressed patients and downregul ation following antidepressant treatments. Herein, imidazoline receptor bin ding protein (IRBP) antiserum was used to quantify imidazoline receptors on platelets of depressed patients before and after treatment with the atypic al aminoketone antidepressant, bupropion. Western blots revealed an increas e in IRBP-immunodensity (p=0.01, two-tailed) in a 33 kDa protein band in un treated depressed patients (n=21) as compared with controls (n=17). This ba nd has been positively correlated with I-1 binding sites on platelets. Foll owing 6 weeks' treatment with bupropion, IRBP-immunodensity was downregulat ed in depressed patients (p=0.03, paired t-test); predominantly in responde rs (p=0.005). Patients non-responsive to bupropion (n=5) were significantly different from responders (p=0.05) by exhibiting no elevation in IRBP-immu nodensity at pre-treatment and no downregulation of the 33 kDa band after t reatment. IRBP-immunodensity was negatively correlated (r=-0.79, p=0.01) wi th plasma concentrations of bupropion and its metabolites at week-4 of BUP treatment. Thus, a 33-kDa IRBP on platelet plasma membranes is elevated in depression and normalized in responders to bupropion. (C) 1999 Elsevier Sci ence Ltd. All rights reserved.