Platelet [³H]-Imipramine Binding Differentiates Major Depression from Alzheimer’s Disease in Elderly

Abstract

The tricyclic antidepressant imipramine binds with high affinity to specific sites in brain (Raisman et al., 1979a, b; 1980; Rehavi et al., 1980; Langer et al., 1981a) and blood platelets (Briley et al., 1979; Paul et al., 1980), which are believed to be associated to the uptake of serotonin (Langer et al., 1981b; Paul et al, 1981; Dumbrille-Ross and Tang, 1981; Sette et al., 1981). In both brain and platelets, the characteristics of [³H]-imipramine binding sites are very similar (Langer et al., 1981b; Paul et al., 1981). Furthermore, these binding sites are decreased in the central nervous system (Stanley et al., 1982) and platelets (Langer et al., 1981b; Briley et al., 1980; Paul et al., 1981; Suranyi-Cadotte et al., 1983) of depressed patients. Hence, platelet [³H]-imipramine binding may be a useful laboratory adjunct to differentiate major depression from other conditions. This may apply particularly to depression in the elderly, where the diagnostic distinction from primary degenerative dementia can be very difficult (McAllister, 1983). Both syndromes can coexist in the same individual (Reifler et al., 1982), and depression itself can present with cognitive impairment in the elderly. An erroneous diagnosis of a non-treatable dementia in a depressed patient has major therapeutic and prognostic implications. The objective of the present study was to investigate the utility of platelet [³H]-imipramine binding in the differential diagnosis of depression from dementia in the elderly.