PLATELET-I-1 IMIDAZOLINE BINDING-SITES ARE DECREASED BY 2 DISSIMILAR ANTIDEPRESSANT AGENTS IN DEPRESSED-PATIENTS

Previous studies have indicated that there may be a dysregulation of a lpha(2)-adrenoceptors and imidazoline receptors in depression. This st udy compares the effects of chronic antidepressant treatment with a se rotonin reuptake inhibitor (fluoxetine) versus a noradrenaline reuptak e inhibitor (desipramine) on the binding parameters of the platelet im idazoline binding site (subtype I-1) and of the platelet alpha(2)-adre noceptor in depressed patients. After 6 weeks of treatment with either antidepressant, platelet I-1 binding sites became normalized (i.e. do wnregulated). A negative correlation was obtained between plasma epine phrine concentrations and platelet alpha(2)-adrenoceptor B-max values within the samples, but no correlation was obtained between any plasma catecholamine and a platelet I-1 binding parameter. An additional fin ding was the increased affinity of alpha(2)-adrenoceptors for p(125)I- clonidine in untreated depressed patients compared to healthy subjects . Because of the density of platelet I-1 binding sites was downregulat ed by both of the antidepressants, we postulate that a decrease in pla telet I-1 binding site density may be related to an improved state fro m depression that these antidepressants produce. Copyright (C) 1996 El sevier Science Ltd.