diphenylhexatriene and Depressive-Disorder

Membrane fluidity and adrenergic receptor binding were studied in platelets of depressed patients before and during treatment with desmethylimipramine to investigate the relationship between the alpha 2-adrenergic receptor and its membrane environment in depression. Most samples came from a previous study in which we observed higher 3H-para-aminoclonidine (3H-PAC) binding in platelets from depressed patients compared to healthy subjects. Fluidity was measured by steady state diphenylhexatriene (DPH) anisotropy in both purified plasma membranes and in intracellular membrane preparations from platelets. No differences were observed in DPH membrane fluidity, per se, indicating that fluidity changes probably do not underlie either the increased alpha 2-adrenergic receptor binding in depression or the normalization of binding during treatment. However, lower intracellular membrane fluidity was correlated with higher binding to 3H-PAC site-1 in healthy subjects, but not in depressed patients. Thus, during depression there may be a disruption in the normal relationship between the adrenergic receptor and its membrane environment.

Topics: Adrenergic alpha-Agonists; Adult; Aged; Blood Platelets; Clonidine; Depressive Disorder; Desipramine; Diphenylhexatriene; Female; Fluorescence Polarization; Humans; Male; Membrane Fluidity; Middle Aged; Psychiatric Status Rating Scales; Radioligand Assay; Receptors, Adrenergic, alpha

Double-blind fluorescence studies of platelet membrane fluidity were conducted at 37 degrees C for 51 patients with Alzheimer-type dementia, 24 nondemented depressed patients, and 50 neurologically healthy subjects. The fluidity of the hydrocarbon region of platelet membranes from the demented group, as reflected by the steady-state anisotropy of the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH), was significantly greater than that for the depressed and normal control subjects. Within the demented group, platelet membrane fluidity was significantly correlated with severity of dementia but not with duration of illness or age at onset. Demented patients with "increased" platelet membrane fluidity had an earlier onset, were more severely demented, and deteriorated more rapidly.

Topics: Aged; Alzheimer Disease; Blood Platelets; Cell Membrane; Depressive Disorder; Diphenylhexatriene; Female; Humans; Male; Membrane Fluidity; Middle Aged; Psychiatric Status Rating Scales; Time Factors